Start relay pin 85 ground location?
08-23-2014, 09:50 AM
#16
Team Owner
Keep Em Flyin!
06-24-2019, 02:53 AM
#17
Burning Brakes
Thread Starter
Sigh, after five problem free years this problem is back. I have had to fight this issue periodically for many years like this. No crank no click, but if I touch 12v to the yellow wire at the 14 pin connector w key in run position, instant start. And the problem is intermittent, it worked yesterday not today and may well work tomorrow.
The problem seems to be a flaky ground and/or connector on the ground wire under the RR quarter panel. This grounds pin 85 allowing 12v to flow to the starter yellow wire. I don’t want to have to pull the rear quarter panel again.
Idea: can I simply wire pin 85 from the back of the CE panel to one of the ground points above the CE panel? It’s crazy that the wire has to travel to the back of the car, on the manual transmission car, just to be grounded there!
Cheers,
Rick
The problem seems to be a flaky ground and/or connector on the ground wire under the RR quarter panel. This grounds pin 85 allowing 12v to flow to the starter yellow wire. I don’t want to have to pull the rear quarter panel again.
Idea: can I simply wire pin 85 from the back of the CE panel to one of the ground points above the CE panel? It’s crazy that the wire has to travel to the back of the car, on the manual transmission car, just to be grounded there!
Cheers,
Rick
06-24-2019, 11:00 AM
#18
Burning Brakes
You can access that ground without removing the quarter panel. There is one or two screws to remove and carefully pull back the panel just enough for access.
06-24-2019, 11:52 AM
#19
Chronic Tool Dropper
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Take a look at the ground point at the front of the spare tire well above the battery. On my later car, there's a plastic shield over the connections and ground, held on with a nut over a welded stud. Wedge-shaped plastic cover, with a sort of a hinged pivot at the rear edge. Anyway, cover comes off, and the connectors for neutral safety and gear selector wiring, fuel pump wiring, and on S4+ cars there's a conductor passing through the connector for the transmission temperature switch (part of the fan control circuitry). The connectors and the ground point may be casually exposed to battery fumes especially if the gasket for the battery lid is deteriorated. IIRC that ground point serves the fuel pump too.
"Tired" electrical connections behave differently when the potential across connector resistance changes. In the case of the starter protection relay, the circuit for the relay coil includes the contacts at the ignition switch, three CE panel connectors, the two relay socket connections, the relay coil, two more connectors at the rear on the way to the switch, the switch connector pins, the switch contact, and the ground point. With the inherent low current demand, even a small resistance buildup in that array of connections and contacts may keep the relay from seeing the voltage it needs to actuate. We stress the need to manage ground point resistance, as those are relatively easy to access and clean, plus most of them affect multiple circuits. Lots of bang for the effort. In this case, with so many the other possible causes, the effort needs to include cleaning and inspecting every possible failure point in the circuit.
Most of the connectors are tinned-pin or brass (copper alloy with tin) "self-wiping" connections, where the simple act of disassembling and reassembling the connector will clean off an oxide barrier layer. Add a spritz of DeOxit or other good contact cleaner to the process, and you improve chances of success even more. I love DeOxit, but in practice I keep 10x larger spray cans of contact cleaner handy for such projects.
Circuit sleuthing that includes pulling any single CE panel connection for cleaning usually means pulling all of them one by one for cleaning. Once I'm in there, with the rugs out and a plastic tray under the CE panel to catch the runoff, it only makes sense to clean all of them. They all live in the same environment after all.
While working on the relay coil circuit like this, you can lift the 14-pin under the hood to prevent the starter from turning. Then go after each element in the switch-side coil circuit with meter and a jumper wire to find the section that's intermittent. With the CE panel cover off, you'll be able to hear the starter interrupt relay click when things are working.
In later cars anyway, the starter interrupt relay is replaced with a socket jumper in manual-gearbox cars. This eliminates the wiring and connections to the rear of the car and puts the solenoid current across the 50 terminals at the ignition switch itself. Others may have a jumper plug in the gearbox switch connector, and have all those potential failure points still in the circuit. Fun Stuff!
"Tired" electrical connections behave differently when the potential across connector resistance changes. In the case of the starter protection relay, the circuit for the relay coil includes the contacts at the ignition switch, three CE panel connectors, the two relay socket connections, the relay coil, two more connectors at the rear on the way to the switch, the switch connector pins, the switch contact, and the ground point. With the inherent low current demand, even a small resistance buildup in that array of connections and contacts may keep the relay from seeing the voltage it needs to actuate. We stress the need to manage ground point resistance, as those are relatively easy to access and clean, plus most of them affect multiple circuits. Lots of bang for the effort. In this case, with so many the other possible causes, the effort needs to include cleaning and inspecting every possible failure point in the circuit.
Most of the connectors are tinned-pin or brass (copper alloy with tin) "self-wiping" connections, where the simple act of disassembling and reassembling the connector will clean off an oxide barrier layer. Add a spritz of DeOxit or other good contact cleaner to the process, and you improve chances of success even more. I love DeOxit, but in practice I keep 10x larger spray cans of contact cleaner handy for such projects.
Circuit sleuthing that includes pulling any single CE panel connection for cleaning usually means pulling all of them one by one for cleaning. Once I'm in there, with the rugs out and a plastic tray under the CE panel to catch the runoff, it only makes sense to clean all of them. They all live in the same environment after all.
While working on the relay coil circuit like this, you can lift the 14-pin under the hood to prevent the starter from turning. Then go after each element in the switch-side coil circuit with meter and a jumper wire to find the section that's intermittent. With the CE panel cover off, you'll be able to hear the starter interrupt relay click when things are working.
In later cars anyway, the starter interrupt relay is replaced with a socket jumper in manual-gearbox cars. This eliminates the wiring and connections to the rear of the car and puts the solenoid current across the 50 terminals at the ignition switch itself. Others may have a jumper plug in the gearbox switch connector, and have all those potential failure points still in the circuit. Fun Stuff!
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Musse (03-17-2024)
06-24-2019, 05:24 PM
#20
Burning Brakes
Thread Starter
Thanks Alex, Dr. Bob! I have two connectors and no grounds in the wheel well. My car is a manual. The first connector is a 4-pin where only 2 pins are used, and the connector acts as a jumper. This is one of the connectors Dr. Bob mentioned that is in between terminal 85 of the relay, and the grounding point under the RR quarter. (If there's a second connector in that ground circuit somewhere, I'd love to know where). And clearly this takes the place of some switch inside the auto transmission cars to prevent starting except when in P or D. The second connector is a 6-pin connector, of which 4 are used, and this appears to include the speedo and reverse light connections among others and is not relevant to my starting problem.
At the RR quarter, even after removing all the screws at the back edge/pillar and cargo holddown, I'm only able to access two connectors at the very back edge, another 2-pin and a larger, circular connector. Neither connector is relevant to terminal 85 (I pulled and reconnected them both while measuring ohms from 85 to ground, and the circuit remained unbroken). I cannot see, feel or access any other connector -- or most importantly the ground point -- without pulling the panel.
FWIW, car started first thing this morning, and the last thing I checked last night was to verify that it didn't start! Also, I measured about 6 ohms from terminal 85 to ground (well, I guess I should subtract about 1 ohm which is what I read when touching measurement leads together), but on two separate occasions the measured ohms started drifting up.The first time it got up to about 10 ohms, then I disconnected and reconnected my leads and it went to normal. Many other tests, wiggles, and connecting/reconnecting tests were solid around 6 ohms. But later, I watched while ohms drifted up... and up... eventually reaching about 60 ohms. Even with lots of wiggling, but not disconnecting, the leads. Crazy. I finally disconnected and, suspecting a voltmeter battery or other issue, immediately touched my two measurement leads together and of course read only about 1 ohm. When I re-tested the ground circuit it was back at 6. I really don't know what to say. Oh, and I also popped the relay back in, and it started.
My plan is to pull out the loopback connector in the spare tire well tonight and test for resistance from a) terminal 85 to the connector; and b) from the connector to ground. Hopefully that can help me isolate which part of the circuit may have an issue.
When I have pulled off the RR quarter panel in the past to look at the ground there, it has always been pristine. I think I've always unplugged and plugged the spare wheel well connectors too, though I may not have understood what they were. I guess I'll see what my resistance readings are from the spare tire area connector to the ground, and unless they are close to zero I'll know it's either a ground point issue or a flaky wire from the connector to ground.
One other note: I'm still leaning toward the conclusion that the ground point back there is OK (and of course don't want to pull the panel). It's always been pristine, no corrosion. And also, note that even when the car doesn't start, the fuel pump and rear lights work fine (I get instant start when touching the yellow wire for the starter). That tends to suggest, but not prove, that the ground itself is ok. (I suppose at some level of resistance, the starter relay won't engage, but the pump circuit would still operate). But it's frustrating that I can't conclusively identify the cause or the fix.
At the RR quarter, even after removing all the screws at the back edge/pillar and cargo holddown, I'm only able to access two connectors at the very back edge, another 2-pin and a larger, circular connector. Neither connector is relevant to terminal 85 (I pulled and reconnected them both while measuring ohms from 85 to ground, and the circuit remained unbroken). I cannot see, feel or access any other connector -- or most importantly the ground point -- without pulling the panel.
FWIW, car started first thing this morning, and the last thing I checked last night was to verify that it didn't start! Also, I measured about 6 ohms from terminal 85 to ground (well, I guess I should subtract about 1 ohm which is what I read when touching measurement leads together), but on two separate occasions the measured ohms started drifting up.The first time it got up to about 10 ohms, then I disconnected and reconnected my leads and it went to normal. Many other tests, wiggles, and connecting/reconnecting tests were solid around 6 ohms. But later, I watched while ohms drifted up... and up... eventually reaching about 60 ohms. Even with lots of wiggling, but not disconnecting, the leads. Crazy. I finally disconnected and, suspecting a voltmeter battery or other issue, immediately touched my two measurement leads together and of course read only about 1 ohm. When I re-tested the ground circuit it was back at 6. I really don't know what to say. Oh, and I also popped the relay back in, and it started.
My plan is to pull out the loopback connector in the spare tire well tonight and test for resistance from a) terminal 85 to the connector; and b) from the connector to ground. Hopefully that can help me isolate which part of the circuit may have an issue.
When I have pulled off the RR quarter panel in the past to look at the ground there, it has always been pristine. I think I've always unplugged and plugged the spare wheel well connectors too, though I may not have understood what they were. I guess I'll see what my resistance readings are from the spare tire area connector to the ground, and unless they are close to zero I'll know it's either a ground point issue or a flaky wire from the connector to ground.
One other note: I'm still leaning toward the conclusion that the ground point back there is OK (and of course don't want to pull the panel). It's always been pristine, no corrosion. And also, note that even when the car doesn't start, the fuel pump and rear lights work fine (I get instant start when touching the yellow wire for the starter). That tends to suggest, but not prove, that the ground itself is ok. (I suppose at some level of resistance, the starter relay won't engage, but the pump circuit would still operate). But it's frustrating that I can't conclusively identify the cause or the fix.
06-24-2019, 07:15 PM
#21
Chronic Tool Dropper
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So 6 Ohms is a lot for a circuit like that. More is worse. Trace back connector by connector from the CE plug after the relay, to the connector in the spare tire well (2 points) to find the component of connector component conductor (any or all) with the resistance.
If still no good/definitive test results, lift the 14-pin (T14 under the hood), and separately energize 50 from the ignition switch in start position, and test for voltage at those same spots but with everything connected. Current through the loop is low so you may end up looking for millivolts.
The wiring diagram shows the circuit from relay pin 85 to CE panel U7, Brown/yellow to spare well 4-pin connector pin 1, back through a brown/yellow jumper to the same spare well 4-pin connector at pin 2, where it changes to brown and on to the chassis ground point 2, which it shares with (at least...):
-- the fuel pump and the fuel sender unit
-- rear window heater
-- hatch alarm switch if so equipped
-- rear window wiper motor
-- right and left rear lamp housings
-- rear roof and hatch interior lights
-- rear lid light switch
-- license plate light
Lots of potential interaction among those users if a ground connection stack isn't excellent from top to bottom. I like to use a brass detailer's toothbrush to brighten each ring terminal under a ground point bolt. The same brush brightens the chassis metal where the bolt threads in, the washer and the bolt head surfaces too. Brush to make the grey surfaces on any tin-plated rings shine a little, brass or copper until bright.
If still no good/definitive test results, lift the 14-pin (T14 under the hood), and separately energize 50 from the ignition switch in start position, and test for voltage at those same spots but with everything connected. Current through the loop is low so you may end up looking for millivolts.
The wiring diagram shows the circuit from relay pin 85 to CE panel U7, Brown/yellow to spare well 4-pin connector pin 1, back through a brown/yellow jumper to the same spare well 4-pin connector at pin 2, where it changes to brown and on to the chassis ground point 2, which it shares with (at least...):
-- the fuel pump and the fuel sender unit
-- rear window heater
-- hatch alarm switch if so equipped
-- rear window wiper motor
-- right and left rear lamp housings
-- rear roof and hatch interior lights
-- rear lid light switch
-- license plate light
Lots of potential interaction among those users if a ground connection stack isn't excellent from top to bottom. I like to use a brass detailer's toothbrush to brighten each ring terminal under a ground point bolt. The same brush brightens the chassis metal where the bolt threads in, the washer and the bolt head surfaces too. Brush to make the grey surfaces on any tin-plated rings shine a little, brass or copper until bright.
06-25-2019, 10:19 PM
#23
Burning Brakes
Thread Starter
Reporting back. I haven’t driven the car. Confusing results, I’m afraid. Have not cleaned or touched RR ground point but have cleaned loopback connector in spare tire area. New battery in multimeter and resistance values below adjusted for lead resistance.
- Total resistance 85 to ground now very low, under 2 ohms
- Resistance from spare tire connector to ground under .1 ohms (this tests the RR ground point, looks good)
Battery voltage 12.6
Voltage at cpe at 3 input connectors 12.58v
The following tests are with 14 pin disconnected
With start relay XIV removed, pin 86 receives 11.9v when in “crank” but over the course of 10 seconds continuously falls to about 11.8v and still falling when test stopped
With relay re-inserted:
Voltage at pin 85 under crank about 170 mV but again over ten or so seconds continuously falls to about 164 mV
Voltage at spare tire connector under same test 12mV falling to about 11.7
Also with 14 pin reconnected the car started.
Seems to me that everything looks quite normal now EXCEPT for the falling input voltage at pin 86 even when relay is removed. I’m assuming that this also causes the falling values at pin 85 (and rear connector) even with the relay in. Is this abnormal? Bad cylinder lock? I hope I can catch the car when it doesn’t start and find out what’s going on. Next steps?
Cheers!
Rick
- Total resistance 85 to ground now very low, under 2 ohms
- Resistance from spare tire connector to ground under .1 ohms (this tests the RR ground point, looks good)
Battery voltage 12.6
Voltage at cpe at 3 input connectors 12.58v
The following tests are with 14 pin disconnected
With start relay XIV removed, pin 86 receives 11.9v when in “crank” but over the course of 10 seconds continuously falls to about 11.8v and still falling when test stopped
With relay re-inserted:
Voltage at pin 85 under crank about 170 mV but again over ten or so seconds continuously falls to about 164 mV
Voltage at spare tire connector under same test 12mV falling to about 11.7
Also with 14 pin reconnected the car started.
Seems to me that everything looks quite normal now EXCEPT for the falling input voltage at pin 86 even when relay is removed. I’m assuming that this also causes the falling values at pin 85 (and rear connector) even with the relay in. Is this abnormal? Bad cylinder lock? I hope I can catch the car when it doesn’t start and find out what’s going on. Next steps?
Cheers!
Rick
06-26-2019, 03:02 AM
#24
Chronic Tool Dropper
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The 86 comes from the igitioon switch 50 (start) contact. I'm not at the WSMs so don't have the exact CE panel connector/pin from the ignition switch. But you get the idea. the 50 circuit there carries enough current to pull in the relay, so not much at all; contact heating should not be an issue. The voltage and resistance numbers you share should be plenty to close the relay.
06-26-2019, 05:56 PM
#25
Burning Brakes
Thread Starter
Hi Dr. Bob,
My plan for now is to keep my multimeter and leads in the car and just drive it until the issue pops back up, then perform all the tests. Seems to me the problem is either, hypothetically, a) too-low voltage on 86; b) too-high resistance on ground from pin 85; or c) intermittent relay issue. I think I may rig a spade connector off the back of terminal 85 with a piece of wire and, if the problem re-appears, touch the wire to ground and try cranking again. If it works that would mean a ground problem, and if no difference then (a) or (c). It's starting just fine now...
In the meantime, two specific questions: Do you think it unusual for the voltage on pin 86 to be nearly .7v less than battery voltage (this is with the relay removed)?
And also, is it unusual for that voltage to fall a tenth of a volt over a few seconds as I observed? (again with relay removed)
Thanks as always, I appreciate your expertise!!!
Rick
My plan for now is to keep my multimeter and leads in the car and just drive it until the issue pops back up, then perform all the tests. Seems to me the problem is either, hypothetically, a) too-low voltage on 86; b) too-high resistance on ground from pin 85; or c) intermittent relay issue. I think I may rig a spade connector off the back of terminal 85 with a piece of wire and, if the problem re-appears, touch the wire to ground and try cranking again. If it works that would mean a ground problem, and if no difference then (a) or (c). It's starting just fine now...
In the meantime, two specific questions: Do you think it unusual for the voltage on pin 86 to be nearly .7v less than battery voltage (this is with the relay removed)?
And also, is it unusual for that voltage to fall a tenth of a volt over a few seconds as I observed? (again with relay removed)
Thanks as always, I appreciate your expertise!!!
Rick
06-26-2019, 08:24 PM
#26
Chronic Tool Dropper
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The voltage from ignition switch terminal 50 should be exactly what you see at relay terminal 86, while the relay is removed. There is no load on that circuit with the relay out.
Power -to- the ignition switch exit the CE panel at A2, where one red conductor goes to the ignition switch and the other to the headlight switch. A2 should read the same voltage to ground as the incoming power 30 rail at the top of the CE panel, where the conductors with power from the jump post are connected.
Power -from- the ignitions starter circuit terminal 50 comes back into the CE panel at terminal A6, which should be a yellow conductor. With key in start position .and. start relay removed, A2 and A6 should have exactly the same voltage, referenced to chassis ground. It should be the same with the relay installed, but test that with the 14-pin underhood connector lifted please or the starter will spin. If those two don't have exactly the same voltage,, look at the electrical part of the ignition switch, the switch connector, and the wiring between the ignition switch and terminal A at the bottom of the CE panel.
Power -to- the ignition switch exit the CE panel at A2, where one red conductor goes to the ignition switch and the other to the headlight switch. A2 should read the same voltage to ground as the incoming power 30 rail at the top of the CE panel, where the conductors with power from the jump post are connected.
Power -from- the ignitions starter circuit terminal 50 comes back into the CE panel at terminal A6, which should be a yellow conductor. With key in start position .and. start relay removed, A2 and A6 should have exactly the same voltage, referenced to chassis ground. It should be the same with the relay installed, but test that with the 14-pin underhood connector lifted please or the starter will spin. If those two don't have exactly the same voltage,, look at the electrical part of the ignition switch, the switch connector, and the wiring between the ignition switch and terminal A at the bottom of the CE panel.
06-26-2019, 08:45 PM
#27
Burning Brakes
Thread Starter
WOW! I've been staring at the diagrams and didn't figure that out. I see it on the current flow diagram, now that you pointed it out exactly (I think I am slowly understanding these diagrams). That is exactly what I need to trace the voltage drop. I can verify that A2 is red, and A6 yellow, from some recent photos I took of the panel. THANKS!!! Will check tonight and report back!
06-27-2019, 01:23 PM
#28
Burning Brakes
Thread Starter
Recording readings for future reference.
XIV relay out, 14 pin disconnected
With no key in ignition, triple input at panel is 12.45V
With key moved to run, input falls to 12.2 initially then to 12.03 over a few secs. I saw this yesterday going straight to “crank” but it really appears to happen whenever the key is moved to run. Perhaps just the effect of load on the battery.
In “crank” after voltage stabilized in “run”:
Panel input 12.03V
A2 11.9V (going to cylinder)
A6 11.75V (coming from cylinder)
86 11.75V (on XIV relay, from A6, same voltage)
There is a slight drop from panel input to A2, and also from A2 to A6 out to cylinder and back. Does the fact that voltages are not identical indicate a problem?
Car starts when everything reconnected.
And now... I wait for the no-start to reappear.
XIV relay out, 14 pin disconnected
With no key in ignition, triple input at panel is 12.45V
With key moved to run, input falls to 12.2 initially then to 12.03 over a few secs. I saw this yesterday going straight to “crank” but it really appears to happen whenever the key is moved to run. Perhaps just the effect of load on the battery.
In “crank” after voltage stabilized in “run”:
Panel input 12.03V
A2 11.9V (going to cylinder)
A6 11.75V (coming from cylinder)
86 11.75V (on XIV relay, from A6, same voltage)
There is a slight drop from panel input to A2, and also from A2 to A6 out to cylinder and back. Does the fact that voltages are not identical indicate a problem?
Car starts when everything reconnected.
And now... I wait for the no-start to reappear.
Last edited by rjtw; 06-27-2019 at 04:14 PM.
06-27-2019, 04:16 PM
#29
Chronic Tool Dropper
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There's no capacitance or other magic involved. When the key moves to RUN (position 2) but the engine isn't running yet, all the normal driving consumers of power are connected and drawing from the battery. Exception is the fuel pump, which draws continuous power only after the ignition generates tach pulses and the fuel pump relay closes. Result: battery terminals drop from 12.6V at-rest voltage closer to 12V with most of the running-the car load attached.
While cranking, only the minimum systems required for running are left connected. Main users like headlights and wipers for instance, have power supplied through either the X contact on the ignition switch or through the X-bus relay that's energized by the ignition switch X connections.
---
Check the battery condition. My annual maintenance protocol includes sampling the electrolyte for specific gravity. A cheap (~~$3) tester from Wal-Mart or your parts store is fine. It has an eye-dropper with colored ***** inside. Each ball is a different density, so a low specific gravity of fluid in the tube may not float the heavier *****. the colors give you an idea of cell condition based on the heaviest ball still floating when you draw a sample from a cell. If any sample has a green ball falling, you are casually comparing battery price and availability. When any yellow ***** are sinking, you are seriously shopping. If any red ***** start falling, immediately take a car other than the 928 to the battery store.
The specific gravity test offers you a little warning before you get stranded. The test must be done with a fully-charged battery, and the battery must be allowed to stabilize for at least 30 mins after charging ceases.
I performed this test a couple months ago now, and showed three yellow (marginal) and one red (critical) cells. the car seemed to start just fine, and the maintainer is connected when I'm not driving. The fancy "smart" maintainer I have (CTEK 7002US) has a recovery mode available, and I figured I had nothing to lose trying that. After one "recovery" round, I have five green and one yellow, so I guess it works to a certain extent. I've driven the car a few times since, just local stuff mostly, and otherwise it's been on the maintainer in normal mode. I'll probably go disconnect things and run it through another "recovery" cycle for grins and see if the $100 maintainer can really extend the life of the $100 replacement-cost battery. It will get a new battery anyway before any touring adventures, just playing and seeing whether the $$ invested in the smart maintainers (3 now...) will ever pay off. So far they are fun and interesting, do great at maintaining plus they supply support voltage while I change batteries in the more, um, "modern" stablemates. All the vehicles have hardwired plugs for the maintainers at this point, so use couldn't be easier.
While cranking, only the minimum systems required for running are left connected. Main users like headlights and wipers for instance, have power supplied through either the X contact on the ignition switch or through the X-bus relay that's energized by the ignition switch X connections.
---
Check the battery condition. My annual maintenance protocol includes sampling the electrolyte for specific gravity. A cheap (~~$3) tester from Wal-Mart or your parts store is fine. It has an eye-dropper with colored ***** inside. Each ball is a different density, so a low specific gravity of fluid in the tube may not float the heavier *****. the colors give you an idea of cell condition based on the heaviest ball still floating when you draw a sample from a cell. If any sample has a green ball falling, you are casually comparing battery price and availability. When any yellow ***** are sinking, you are seriously shopping. If any red ***** start falling, immediately take a car other than the 928 to the battery store.
The specific gravity test offers you a little warning before you get stranded. The test must be done with a fully-charged battery, and the battery must be allowed to stabilize for at least 30 mins after charging ceases.
I performed this test a couple months ago now, and showed three yellow (marginal) and one red (critical) cells. the car seemed to start just fine, and the maintainer is connected when I'm not driving. The fancy "smart" maintainer I have (CTEK 7002US) has a recovery mode available, and I figured I had nothing to lose trying that. After one "recovery" round, I have five green and one yellow, so I guess it works to a certain extent. I've driven the car a few times since, just local stuff mostly, and otherwise it's been on the maintainer in normal mode. I'll probably go disconnect things and run it through another "recovery" cycle for grins and see if the $100 maintainer can really extend the life of the $100 replacement-cost battery. It will get a new battery anyway before any touring adventures, just playing and seeing whether the $$ invested in the smart maintainers (3 now...) will ever pay off. So far they are fun and interesting, do great at maintaining plus they supply support voltage while I change batteries in the more, um, "modern" stablemates. All the vehicles have hardwired plugs for the maintainers at this point, so use couldn't be easier.
06-30-2019, 03:02 AM
#30
Burning Brakes
Thread Starter
Some “final” thoughts on this issue for anyone else with a similar problem. Although this happened to me twice in the last five years and I couldn’t conclusively prove the cause either time, I am of the opinion that the loopback connector in the spare tire well is the real culprit. As soon as I cleaned that connector this time around, the resistance of pin 85 to ground went from 5-6 ohms (or more) to under 2 ohms and the problem disappeared. Last time around, I likewise cleaned that connector and also checked the actual ground point which looked brand new. I still need to test my battery and yes, Dr Bob is right, a less than fully healthy battery may well have been a contributing cause (with too-high ground resistance) and not allowing the starter relay to be triggered properly.
In any event, I’ve decided to perform sacrilege and not rely on the ridiculous rear ground circuit for pin 85. The ground leaves the central panel via connector U, pin 7. That line does not ground anything else just pin 85. I plan to simply remove the female connector from connector U (leaving it covered to prevent contact with anything else but unconnected at the base of the panel) and insert a new female connector attached via a short lead (brown 1mm2) to a ring connector which I will ground at one of the ground points above the panel. The nice part of this is that it’s easily and fully reversible. Of course, this only works properly for a manual car. That should provide a permanent, corrosion free low resistance ground and hopefully a PERMANENT fix to this recurring problem!! Will report back if it ever crops up!!
Dr Bob, thanks again for all your superlative guidance!!
In any event, I’ve decided to perform sacrilege and not rely on the ridiculous rear ground circuit for pin 85. The ground leaves the central panel via connector U, pin 7. That line does not ground anything else just pin 85. I plan to simply remove the female connector from connector U (leaving it covered to prevent contact with anything else but unconnected at the base of the panel) and insert a new female connector attached via a short lead (brown 1mm2) to a ring connector which I will ground at one of the ground points above the panel. The nice part of this is that it’s easily and fully reversible. Of course, this only works properly for a manual car. That should provide a permanent, corrosion free low resistance ground and hopefully a PERMANENT fix to this recurring problem!! Will report back if it ever crops up!!
Dr Bob, thanks again for all your superlative guidance!!
Last edited by rjtw; 06-30-2019 at 03:18 AM.