No 12v from alternator exciter cable
 

1992 Volvo 940 GL non-turbo.

Hey Guys, I'm still having issues with the alternator charging on my 1992 Volvo 940 GL non-turbo, but the problem seems to be deeper than just swapping some major parts like the alternator and battery.


Here is what I did to the car so far.

- went through two new alternators thinking the first was defective

- new battery

- checked and cleaned ground wires from alternator.

- a few new bulbs and some fresh solder in some areas of the instrument cluster

symptoms that might help you guys figure out what's going on.

- upon replacing the old ORIGINAL alternator, there was a great 14v charge while running for about a week, then nothing. only 12v from the battery.

- we have tracked this problem down to no voltage coming from the exciter wire that plugs into the alternator.

- no warning lights except seatbelt and overdrive when key is in and in position 2, car engine is not running. (overdrive relay has been acting up for years now so I doubt it's causing the issue)

- when ignition is in position 2, blower and electricals work, but as soon as the car starts, the electricals are off. When I then move around the key and wiggle it around, things turn back on. This also randomly happens while driving. A simple key wiggle turns things back on.


- don't know if this is related, but only the back speakers and the front left dash tweeter work, It's been like that for a few years as well. I'm thinking blown speakers.

Some questions

- could either the ignition lock cylinder or ignition switch be causing this?
- could one burnt out warning light be causing ALL of them not to work?

- could the overdrive relay be messing things up?

The alternator exciter line is supplied 12volts through the key and also illuminates the idiot light if not charging when running.
If you have to wiggle the key to operate electrical functions, that's not good.
If the key is in the on, number 2 position, you should see 12 volts at the back of you alternator field line.
If not, I'd suspect the key would be a good place to start.

indeed, if that alternator light doesnt come on before you start the motor, then the alternator won't work when you do start the motor.

if wiggling the key is causing electrics to go on and off, then you need to replace the ignition switch behind the lock cylinder.

okay, I'm going to pick up an ignition switch today and see if that helps.

Okay so after replacing the ignition switch the warning lights now work, and the alternator is charging. BUT..

Seems like sometimes the warning lights don't work, but after around 10-20min of driving they work again, and they stay on normally after that (so far). I'm guessing the heat in the cabin and the engine bay have something to do with this. I will keep updating you guys with symptoms though. For now I have a car that won't get stuck with no charge at least...

When the warning lights work, the SRS light is on, when they don't work, my overdrive light is on (remember the relay is screwy)

bad grounds behind the dashboard can cause screw stuff like that, so can corroded wiring from water intrusion.

Sounds like the instrument panel circuit board solder is in need of a refloat. Minor cracks develop, cause the problems you describe...


see this:
https://www.brickboard.com/FAQ/700-9...anelRepair.htm

Another thing to check is the two main connectors to the instrument panel. Our '90 240 used to experience periodic dropout of the whole instrument cluster. I pulled it out and found that there was extreme dirt on the two circular connectors. Cleaned it up nicely and the problem has not returned.

I have the same thing. It only happens when it's cold outside. My gauges, dash lights, speedometer (works at about half speed), etc. don't operate normally. I can sometimes move my dash light level switch back and forth and it can help speed up the process. Sometimes, flipping on my fog lights, honking my horn, or anything that draws current, can sometimes get all to work. Usually though, Once things warm up inside, all "clicks" on and everything works again until the next cold start. Here in L.A. with warm summers, I won't see it for months.

My Swedish mechanic told me there is a cold sensitive relay that would have to changed out in the dash. After the labor involved, I decided to just live with it. Now, it's been probably ten to twelve years of just dealing with it.