Voltage gauge waay high, way low
#31
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Tim - you need to take it to a place that specializes in alternator rebuilds. They should have a load bench setup that can run for a while with a current load on the output and monitor voltage & current - I very much doubt Autozone does more than a very cursory & brief check.... its not going to be enough for this case.
Alan
Alan
#32
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
Tim - you need to take it to a place that specializes in alternator rebuilds. They should have a load bench setup that can run for a while with a current load on the output and monitor voltage & current - I very much doubt Autozone does more than a very cursory & brief check.... its not going to be enough for this case.
Alan
Alan
So at least during that more thorough bench testing, this remanufactured alternator seemed okay. I am truly curious about the possibility of a grounding issue here. The guy who ran the test (his name was Dusty - really) suggested that an alternator will mistakenly crank out more volts if it thinks the battery is dead. There is no battery wire run to this type of alternator, but a problem ground could cause such a mistake. The fact that the spiking happens most commonly in wet weather conditions has be wondering if there is wiring insulation issues somewhere. Within the main wiring harness maybe?
Ready for the next test. I'm open to all suggestions
Continued thanks...
#33
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Well its hard to imagine the alternator isn't well grounded the way its bolted to the block. So that would leave the battery ground or battery supply if there is any chance it disconnects.
This can cause erratic voltages or spiking but usually not to the extent or stability that you are seeing.
I understood you had already replaced the battery and ground strap - which seemed to rule that out.
One option is to run leads to the battery posts direct and back to your DMM located where you can see it.. then see if you ever get a case where the DMM says ~12.8v and the car gauge looks like 16-18v. That would be very interesting...
Usually when you have any issues with the battery not providing enough load/store to stabilize the regulator it also shows up in very weak starter cranking - or occasional failure to crank at all... have you experienced this at all recently?
Alan
This can cause erratic voltages or spiking but usually not to the extent or stability that you are seeing.
I understood you had already replaced the battery and ground strap - which seemed to rule that out.
One option is to run leads to the battery posts direct and back to your DMM located where you can see it.. then see if you ever get a case where the DMM says ~12.8v and the car gauge looks like 16-18v. That would be very interesting...
Usually when you have any issues with the battery not providing enough load/store to stabilize the regulator it also shows up in very weak starter cranking - or occasional failure to crank at all... have you experienced this at all recently?
Alan
#34
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
Nope. Car turns over just fine all the time.
#35
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
I'm guessing that would isolate the problem to the alternator. But I'm still curious about voltage leaks within the wiring harness and at the jump post. If water was getting into the circuitry, could that create an unwanted ground and then "pull" more voltage from the alternator? Same way that a dying battery might cause such a pull?
See if it happens... if yes it questions the battery itself, the battery ground strap to the frame, the engine ground strap, the battery feeder to the starter or the starter to alternator connection. much of this is newly replaced...
If any of these other than the starter to alternator connection were intermittent - the car would not start reliably...
It does throw suspicion on that starter to alternator connection - but its actually usually a reliable one...
Check the smaller connection to the large stud of the starter motor - clean the ring terminals well and assemble tightly... similarly check the alternator connections - are all of them clean and secure to the alternator large stud.
Alan
Last edited by Alan; 03-25-2008 at 11:49 PM.
#36
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
March 30 update:
Dave McKenzie assisted me with the reinstallation of the alternator yesterday. In doing so, he noted that the ground wire that splits off of the alternator cabling bundle and connects to the oil pan was unplugged from its connection point. This wire is extrememly brittle and and I tried to repair it when I was replacing the oil pan gasket.
We crimped the female connection end of this wire and Dave snapped it back on to the oil pan connection.
This morning, I took the car out in slightly damp weather. On its third start, the voltage jumped to 16.6V for about 10 seconds and then settled back to 14.2V.
I will reinvestigate the connections between battery, starter, and alternator. I thought that, after start-up, the starter no longer factored into the electronics. But I'm reading Alan to say that if the wiring between the started and alternator is compromised, the alternator can think that the battery is not working and then possibly elevate its voltage output.
Continued thanks.
Dave McKenzie assisted me with the reinstallation of the alternator yesterday. In doing so, he noted that the ground wire that splits off of the alternator cabling bundle and connects to the oil pan was unplugged from its connection point. This wire is extrememly brittle and and I tried to repair it when I was replacing the oil pan gasket.
We crimped the female connection end of this wire and Dave snapped it back on to the oil pan connection.
This morning, I took the car out in slightly damp weather. On its third start, the voltage jumped to 16.6V for about 10 seconds and then settled back to 14.2V.
I will reinvestigate the connections between battery, starter, and alternator. I thought that, after start-up, the starter no longer factored into the electronics. But I'm reading Alan to say that if the wiring between the started and alternator is compromised, the alternator can think that the battery is not working and then possibly elevate its voltage output.
Continued thanks.
#37
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
Connected DMM to battery posts. Started car from cold and gauge briefly rose to 16. DMM also read 16. Twice more the gauge spiked and the DMM spiked with it. Thus, the battery was putting out the increased voltage as well.
Restarted the car a couple times after taking it for a brief spin. Most of the time, the DMM read 14.2V.
In the last trial, I waited about 10 minutes to restart the car. Upon start, the gauge dropped to 10V. The DMM read 11.97V (with the headlights on). Drove the car for about five minutes and the voltage never returned to normal.
So does this prove that the alternator is funky?
Continued thanks to Alan and Roger!
#38
Rennlist Member
Tim and Alan and other electrical guru's,
It seems to me the problem here is voltage spikes. I've heard that if you disconnect your battery while the engine is running (WHICH YOU SHOULD NEVER DO) you will cause voltage spikes. Is there a way that something could be causing a poor connection to your battery, making your alternator think you are disconnecting the battery?
It seems to me the problem here is voltage spikes. I've heard that if you disconnect your battery while the engine is running (WHICH YOU SHOULD NEVER DO) you will cause voltage spikes. Is there a way that something could be causing a poor connection to your battery, making your alternator think you are disconnecting the battery?
#39
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
#40
Team Owner
Please reinspect your hot post connections with battery disconnected . this will include removing the 11mm securing bolt and then opening up both sides of the 14 pin connector. You will be looking for shredded/crumbling wire insulations , make a diagram of the wires positions so they dont fall out whilest your working on the connector, Look down the black insulation and see if the insulation is good here as well you may need to install some heatshrink on the fouled up wires, and clean everything with a pink eraser and then install the hot post cover for a 88 S4 dont let the car get wet till your hot post cover is in place
#41
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Tim - The battery serves 3 purposes:
1) Start the car - provide power to the starter and ECU's before the alternator starts generating.
2) Serve as a stabilizing load for the alternators regulator to maintain stable voltage
(and meanwhile recharge to be ready for Job 1 next time).
3) Serve as a backup power source under high electrical load & low rpm conditions (where the alternator may not be able to generate all the power needed - should be a very rare occurrance).
Tim is not seeing voiltage spikes - he is seeing consistent substantially elevated system voltage. Voltage spikes are characterized as very short duration (in the case of an alternator usually related to the field rotation per phase) and not a high rms value. Clearly we aren't seeing that here and we know there is a good connection to the battery.
I told Tim in a PM that battery - internal damage - is also a possible issue but seems umnlikely since I believe it is new since ths problem surfaced.
The jump post doesn't figure in the connection of the Alternator to the Starter to the Battery - which in any case we know is good...
The alternator exhibits both poor regulation (stable high voltage) and failure to initiate some of the time. Whilst there could be several issues together - the Alternator is the most suspect here and much of the rest (even the alt) are new...
I suggested some tests to Tim - ideally the alternator shop could test his alternator and battery together...
Alan
1) Start the car - provide power to the starter and ECU's before the alternator starts generating.
2) Serve as a stabilizing load for the alternators regulator to maintain stable voltage
(and meanwhile recharge to be ready for Job 1 next time).
3) Serve as a backup power source under high electrical load & low rpm conditions (where the alternator may not be able to generate all the power needed - should be a very rare occurrance).
Tim is not seeing voiltage spikes - he is seeing consistent substantially elevated system voltage. Voltage spikes are characterized as very short duration (in the case of an alternator usually related to the field rotation per phase) and not a high rms value. Clearly we aren't seeing that here and we know there is a good connection to the battery.
I told Tim in a PM that battery - internal damage - is also a possible issue but seems umnlikely since I believe it is new since ths problem surfaced.
The jump post doesn't figure in the connection of the Alternator to the Starter to the Battery - which in any case we know is good...
The alternator exhibits both poor regulation (stable high voltage) and failure to initiate some of the time. Whilst there could be several issues together - the Alternator is the most suspect here and much of the rest (even the alt) are new...
I suggested some tests to Tim - ideally the alternator shop could test his alternator and battery together...
Alan
Last edited by Alan; 04-01-2008 at 04:34 PM.
#42
Team Owner
please check the 14 pin connectorat the hot post for damaged insulation, alternator wires go through this and this could be part of your problem.Battery disconnected.
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
#43
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
please check the 14 pin connectorat the hot post for damaged insulation, alternator wires go through this and this could be part of your problem.Battery disconnected.
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
I've already begun this cleaning, following your earlier post. Took snapshots of where all the pins, both male and female, go. There is only minor corrosion here, though a little eraserheading might help. I see no apparent wiring damage here, but will inspect more closely.
In the meantime, my main man Roger Tyson is sending along another alternator. One by one, we'll eliminate variables and get to da bottom of dis.
Thanks for your suggestion.
Tim
#44
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
please check the 14 pin connectorat the hot post for damaged insulation, alternator wires go through this and this could be part of your problem.Battery disconnected.
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Thus the battery is connected at all times... lets not go in circles here... cleaning the battery posts would make more sense.
The only possible battery connection fault given the measurements taken is an intermittent internal open circuit - this would certainly also manifest in a no-start condition at least some of the time - but apparently does not...
Tim - you did have the DMM connected directly to both the positive and negative battery terminals directly right?
Alan
#45
Addict
Rennlist Member
Artist Formerly Known As 84totheFloor
Rennlist Member
Artist Formerly Known As 84totheFloor
Thread Starter
please check the 14 pin connectorat the hot post for damaged insulation, alternator wires go through this and this could be part of your problem.Battery disconnected.
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Make sure to get a hot post/14pin connector cover( from the 88 S4) after your done and dont let the car get wet till you do
Thanks.