1992 940GL Alternator Exciter wire no voltage.

alext72888 · Post by **alext72888** » 18 Nov 2014, 09:07

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 such as the alternator or 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?

93Regina · Post by **93Regina** » 18 Nov 2014, 10:58

alext72888 wrote: - we have tracked this problem down to no voltage coming from the exciter wire that plugs into the alternator.

Is the alternator warning light on/off when key is switched to on position, with engine not running?

alext72888 · Post by **alext72888** » 18 Nov 2014, 12:17

its off regardless of what you do with the engine or the key. Always off. We checked the bulb and it was fine.

93Regina · Post by **93Regina** » 18 Nov 2014, 14:11

alext72888 wrote:....its off regardless of what you do....

Your instrument-cluster's printed circuit board may have a break in copper line(s), your electrical plug(s) that feed it may not be feeding it voltage....etc.

One could hookup an exciter wire, that is manually controlled, or via light bulb hooked to a switched circuit.

Also, if you jerk the cluster, might fix the key switch also.

Electrical: Instruments

940 Instrument Cluster Removal

740/940Instrument Cluster Repair (1991+)

Volvo 700/900 Speedometer Repair

alext72888 · Post by **alext72888** » 19 Nov 2014, 09:02

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)

lummert · Post by **lummert** » 19 Nov 2014, 10:51

I had a bad main head light relay that caused the overdrive light to come on, head lights not come on, and intermittent stalling that was cured by replacing the relay. It was the rectangular relay that's the size of 2 standard relays on my 1988 760 Turbo.

Karander · Post by **Karander** » 08 Oct 2018, 15:55

Anyone try bypassing the instrument cluster and using a diode in-line to alternator? Check out this video