Battery draining
10-05-2006, 03:32 AM
#61
Drifting
Thread Starter
Two steps forward, one step back...
Before starting the process all over again, I decided to test the current with the suspicious third party accessories disconnected. Namely, the radar detector which I had never turned on, and the stereo.
Stereo: bingo! There was a wire coming off one of the main power feeds into the fuse panel, so my initial test was to just pull the fuse. First, I tested to see that the current was still where I had it measured before (.15) and it was. Then I pulled the fuse and tried it again. Down to .01! Yes!. Went to start the car to verify that everything still worked; it fired right up, no new issues. There was still a buzzing coming from the panel area as reported before. See photo
. The white circle shows the location of the relay that buzzes, and the red circle shows the fuse pulled that reduced the current. I determined which relay was buzzing by touching it; definite vibration.
Here are the numbers that are on this relay:
* 928 615 117 00
* there's a schematic on one side with the numbers 30 85 86 87 on it
* 3rd side reads 12v max 25A
What is this for?
I traced the wire leading from the fuse I pulled to verify it's use, and found this rat's nest of wires and stereo components under the passenger seat:
To confirm that the stereo was the purpose of the wiring, I turned on the stereo with the fuse in, confirmed that it was working the same, and pulled the fuse. The stereo continued to play but only through the rear speakers. That's an acceptable solution for me until I can have the stereo redone, which I intended to do eventually anyway.
Now that "step back". Starting to clean up, and put things back. Fuse still pulled, reconnect the power antennae wire from Monday, and start the car again. No go. Dash lights very dim. No stereo. Starter doesn't engage at all. Car acts like battery is dead, but testing it with the multimeter shows that it's still just a bit below 12v after all this, measured from the end of the grounding strap. Made sure strap is solidly grounded, still no start. I don't really think it's a low battery, but I put it back on the trickle charger until tomorrow morning to be sure.
Did I blow a circuit somewhere?
Before starting the process all over again, I decided to test the current with the suspicious third party accessories disconnected. Namely, the radar detector which I had never turned on, and the stereo.
Stereo: bingo! There was a wire coming off one of the main power feeds into the fuse panel, so my initial test was to just pull the fuse. First, I tested to see that the current was still where I had it measured before (.15) and it was. Then I pulled the fuse and tried it again. Down to .01! Yes!. Went to start the car to verify that everything still worked; it fired right up, no new issues. There was still a buzzing coming from the panel area as reported before. See photo
Here are the numbers that are on this relay:
* 928 615 117 00
* there's a schematic on one side with the numbers 30 85 86 87 on it
* 3rd side reads 12v max 25A
What is this for?
I traced the wire leading from the fuse I pulled to verify it's use, and found this rat's nest of wires and stereo components under the passenger seat:
To confirm that the stereo was the purpose of the wiring, I turned on the stereo with the fuse in, confirmed that it was working the same, and pulled the fuse. The stereo continued to play but only through the rear speakers. That's an acceptable solution for me until I can have the stereo redone, which I intended to do eventually anyway.
Now that "step back". Starting to clean up, and put things back. Fuse still pulled, reconnect the power antennae wire from Monday, and start the car again. No go. Dash lights very dim. No stereo. Starter doesn't engage at all. Car acts like battery is dead, but testing it with the multimeter shows that it's still just a bit below 12v after all this, measured from the end of the grounding strap. Made sure strap is solidly grounded, still no start. I don't really think it's a low battery, but I put it back on the trickle charger until tomorrow morning to be sure.
Did I blow a circuit somewhere?
10-05-2006, 04:57 AM
#62
Rennlist Member
Not likely, with all those symptoms. More likely the + cable is loose, or you didn't hook the power feeds to the CE panel. Check ALL of your work....
10-05-2006, 05:38 AM
#63
Under the Lift
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If this is a 79, the relay you have circled is XI, the AC compressor relay, but the PN is not correct. It should be 928.618.105.00
https://www.928gt.com/t-7879fuse.aspx
https://www.928gt.com/t-7879fuse.aspx
10-05-2006, 12:52 PM
#64
Drifting
Thread Starter
It works! After taking a charge all night, this morning it fires right up.
The patient is is resting comfortably at home, with everything hooked up except the fuse for the amp. So that will be the real test, I guess, to see if the battery drain has really been eliminated.
Dave, I hear what you're saying about loose cable/checking connections, but I did all that last night. I really thought I blew something. Is it possible something got overloaded for a brief period?
Bill, that's that great chart. But what I wrote down is what's actually in that plug. Looking at the chart, it's immediate neighbors aren't supposed to have that number in it, and obviously *something* has to be in that plug for it to start. So maybe it's not *right*, but close enough to work. When I tested all the fuses, relays and plugs I was careful to only remove one at a time and then put them back where they came from before moving on to the next one. So I'm sure that it's where it was when I got the car. But that doesn't mean the previous owners did everything right.
So I'm thinking that my next project will be to audit the fuses and relays - with the help of your chart - to be sure they are correct.
The patient is is resting comfortably at home, with everything hooked up except the fuse for the amp. So that will be the real test, I guess, to see if the battery drain has really been eliminated.
Dave, I hear what you're saying about loose cable/checking connections, but I did all that last night. I really thought I blew something. Is it possible something got overloaded for a brief period?
Bill, that's that great chart. But what I wrote down is what's actually in that plug. Looking at the chart, it's immediate neighbors aren't supposed to have that number in it, and obviously *something* has to be in that plug for it to start. So maybe it's not *right*, but close enough to work. When I tested all the fuses, relays and plugs I was careful to only remove one at a time and then put them back where they came from before moving on to the next one. So I'm sure that it's where it was when I got the car. But that doesn't mean the previous owners did everything right.
So I'm thinking that my next project will be to audit the fuses and relays - with the help of your chart - to be sure they are correct.
10-05-2006, 12:55 PM
#65
Drifting
Thread Starter
Originally Posted by bronto
and obviously *something* has to be in that plug for it to start.
10-05-2006, 01:58 PM
#66
Rennlist Member
I went back and re-read your post -- the AC relay is connected to the tach signal. The car will not run right with a standard relay there. It has to be the correct "speed relay" for the AC, or nothing. If it won't run with that socket empty, you'll have to dig in and figure out what's been hacked.
10-05-2006, 02:13 PM
#67
Drifting
Thread Starter
Now I'm lost. It's running now, with the relay I listed in the socket I circled in the photo. It may be the wrong relay, but it's apparently close enough to work.
The only difference between now and last night was that I put the battery on the charger last night. Why that made a difference is a bit mysterious.
The only difference between now and last night was that I put the battery on the charger last night. Why that made a difference is a bit mysterious.
10-05-2006, 02:30 PM
#68
Rennlist Member
OK, you said the relay is buzzing, right? That's because the tach signal is connected to that socket properly, and is being grounded through the relay coil. You should note that the buzzing changes pitch with engine speed. If everything were wired properly, the car should run without a relay in the AC relay socket. If it won't run without that relay, that to me is very suspicious. There is nothing about the way the car is wired from the factory that would cause this behavior, which is why I made the comment about trying to figure out what's been hacked.
10-05-2006, 03:55 PM
#69
Drifting
Thread Starter
Got it. I've not tried to run the car without that relay, nor have I paid attention to variation in pitch according to RPMs. But I will try that tonight.
10-05-2006, 04:04 PM
#70
Under the Lift
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Order the correct relay.
Funny, now when I click on the PN in the link I provided, it no longer finds the part in 928 Specialists' ordering system. Give them a call or find it elsewhere.
Check around your panel too. Perhaps that relay got swapped into another hole. It might work, but things will work better with the right relays in the right holes.
Funny, now when I click on the PN in the link I provided, it no longer finds the part in 928 Specialists' ordering system. Give them a call or find it elsewhere.Check around your panel too. Perhaps that relay got swapped into another hole. It might work, but things will work better with the right relays in the right holes.
10-05-2006, 05:02 PM
#71
Rennlist Member
If it's wired correctly, having a standard relay in that socket may run OK at idle but the engine will cut out at mid-to-upper RPM ranges. Don't ask me how I know. 
10-05-2006, 05:24 PM
#72
Drifting
Thread Starter
I would like to know
I'm 99.9% certain that this is how it was when I got the car in early August, and that included a run home through the Utah/Nevada desert from Denver. We didn't push it *too* hard, but did hit 105mph at one point. Still pretty low revs I guess. I've been fairly gentle with it other than that. Under what conditions would I see a problem?
I'm 99.9% certain that this is how it was when I got the car in early August, and that included a run home through the Utah/Nevada desert from Denver. We didn't push it *too* hard, but did hit 105mph at one point. Still pretty low revs I guess. I've been fairly gentle with it other than that. Under what conditions would I see a problem?
10-05-2006, 08:07 PM
#73
Rennlist Member
When I put a standard relay in there in my n00b ignorance, it would stumble at idle and begin cutting out around 3500RPM. I imagine the inductance of the coil affected the tach signal, but not enough to kill the motor completely under all circumstances.
Basically, the correct relay employs a frequency counter attached to the tach signal to keep the AC clutch disengaged at low RPM, while cranking.
Basically, the correct relay employs a frequency counter attached to the tach signal to keep the AC clutch disengaged at low RPM, while cranking.
10-06-2006, 02:34 AM
#74
Drifting
Thread Starter
Well, this is getting annoying. But I'm beginning to suspect a 2nd problem. I'll not leave out any details in the event some little thing triggers a helpful thought.
Got home, excited to test the above solution. Car starts right up. Yea! Turn it off.
As suggested, observe "buzzing" in sync with the rpms. Start up again without giving any gas to keep revs low, and notice that the voltage warning stays on. Note low frequency buzz from the relay. Rev motor, buzzing stops and voltage light goes out. For the buzzing, I take this as confirmation that the buzz is in sync with RPMs since it changed with the rpms. Turn off motor.
Heed warning that a standard relay shouldn't be in that plug, but that no relay should be OK. Pull relay, start car, confirm buzzing is gone. Note that at low idle voltage warning is on. Turn off motor.
Latch the battery cover and put the spare back in place and cover to go for a drive. Start motor with no gas, voltage warning is on. Rev motor, goes off, idle, stays on. Turn on lights. "Taillight" warning goes on. With lights on/engine running, get out and check rear lights. Sure enough, right tail marker light is out. Left is on. Get back in car and drive around the block. All seems well except (I'm really paying attention) the voltage warning is on at low idle. Come back, park, stop motor.
Remove taillight lens and pull bulb. Glass comes out without the socket, so I'm kind of relieved that its just a bad bulb. I should be so lucky. I put in a new bulb, and it still doesn't work. (I'm testing it by starting the car and turning on the lights. Do they come on otherwise?) Try another bulb, still fails. Do a visual check of the fuse panel, all look OK.
Intend to check circuit with multimeter. Go to start car, and the battery barely turns it enough to start, but it does. Rev the engine high enough for the voltage warning to go off, run it there for a minute, turn off motor. Try to start again, and the starter motor just clicks. As it does this the interior lights dim way down and stereo face goes out.
From here on, the start motor doesn't even click.
Note that through out this, there were numerous engine starts that were very strong, then a precipitous drop off in cranking power. This is a brand new battery. Use multimeter to test battery voltage, and from strap to strap it's 12v. This is the same phenomena as last night. Suddenly steep drop in cranking power, although battery tests with full voltage. I don't know what the heck is going on.
* Is there any component of the ignition/power system that can impede the flow of power at a sudden dropping rate like this?
* What does the voltage warning issue suggest? I can't say for certain that it hasn't done this for a while; driving mostly during the day, it's not a terribly bright light. I can say for certain that it didn't do this before I took it to the mechanic, but at that time it idled high - about 1000 rpm. That might have been high enough to keep it from coming on. It idles much lower now.
* This power dropoff issue is coincidental with pulling the stereo amp fuse; is there any possible way that could affect things?
* Is the taillight issue just a coincidence?
* I am wondering if the trickle charge last night accomplished anything, since the battery tested high last night too. I am leaving everything hooked up tonight, and will be curious to see if the cranking power "comes back" on it's own overnight.
* Bad/incorrect battery?
Got home, excited to test the above solution. Car starts right up. Yea! Turn it off.
As suggested, observe "buzzing" in sync with the rpms. Start up again without giving any gas to keep revs low, and notice that the voltage warning stays on. Note low frequency buzz from the relay. Rev motor, buzzing stops and voltage light goes out. For the buzzing, I take this as confirmation that the buzz is in sync with RPMs since it changed with the rpms. Turn off motor.
Heed warning that a standard relay shouldn't be in that plug, but that no relay should be OK. Pull relay, start car, confirm buzzing is gone. Note that at low idle voltage warning is on. Turn off motor.
Latch the battery cover and put the spare back in place and cover to go for a drive. Start motor with no gas, voltage warning is on. Rev motor, goes off, idle, stays on. Turn on lights. "Taillight" warning goes on. With lights on/engine running, get out and check rear lights. Sure enough, right tail marker light is out. Left is on. Get back in car and drive around the block. All seems well except (I'm really paying attention) the voltage warning is on at low idle. Come back, park, stop motor.
Remove taillight lens and pull bulb. Glass comes out without the socket, so I'm kind of relieved that its just a bad bulb. I should be so lucky. I put in a new bulb, and it still doesn't work. (I'm testing it by starting the car and turning on the lights. Do they come on otherwise?) Try another bulb, still fails. Do a visual check of the fuse panel, all look OK.
Intend to check circuit with multimeter. Go to start car, and the battery barely turns it enough to start, but it does. Rev the engine high enough for the voltage warning to go off, run it there for a minute, turn off motor. Try to start again, and the starter motor just clicks. As it does this the interior lights dim way down and stereo face goes out.
From here on, the start motor doesn't even click.
Note that through out this, there were numerous engine starts that were very strong, then a precipitous drop off in cranking power. This is a brand new battery. Use multimeter to test battery voltage, and from strap to strap it's 12v. This is the same phenomena as last night. Suddenly steep drop in cranking power, although battery tests with full voltage. I don't know what the heck is going on.
* Is there any component of the ignition/power system that can impede the flow of power at a sudden dropping rate like this?
* What does the voltage warning issue suggest? I can't say for certain that it hasn't done this for a while; driving mostly during the day, it's not a terribly bright light. I can say for certain that it didn't do this before I took it to the mechanic, but at that time it idled high - about 1000 rpm. That might have been high enough to keep it from coming on. It idles much lower now.
* This power dropoff issue is coincidental with pulling the stereo amp fuse; is there any possible way that could affect things?
* Is the taillight issue just a coincidence?
* I am wondering if the trickle charge last night accomplished anything, since the battery tested high last night too. I am leaving everything hooked up tonight, and will be curious to see if the cranking power "comes back" on it's own overnight.
* Bad/incorrect battery?
10-06-2006, 02:47 AM
#75
Drifting
Thread Starter
As I hit the submit button for the above, it occurred to me that surely someone is going to suggest (again) that I have a bad positive battery connection. I don't know for sure the best place to test this, but I figured that the "jump start" post in the engine compartment would be a good test; if that's 12v, then it should be good(?). Well, this is interesting. I connected the multimeter, and sure enough it's 12v. But I left it connected, and over the next 30-45 seconds or so it descended all the way down to 0v. Went back to the battery itself, and it's still 12v. Went back to the jump post, and it's still 0v.
What the heck????
What the heck????