924Board.org

[bureau13]

I wasn't paying attention and didn't notice I no longer get the charging light when ignition is moved to ON, and of course the battery went dead. Thinking the bulb in the dash might be burned out, and since I need to replace the steering column bushing anyway, I pulled the steering wheel and console switches, and popped out the gauge with the charging light. However, when I put voltage across the pins that connect to blue and black wires (I believe blue is the alternator excitor terminal and black is +12V from the ignition switch?) the bulb lights up just fine.

With ignition ON and car not running, the blue wire from the alternator seems to be grounded, as it should be. But I'm not getting +12V at the black wire.

Before I tear even more stuff apart to try to get to the ignition switch...does that seem a likely culprit? The car starts and runs fine, so I'm skeptical that the ignition switch is not working correctly. If that output were bad, wouldn't there be other symptoms?

Possible other hint, with ignition ON, none of the lamps along the left side of that gauge light up. The ones on the right side do. I don't know for a fact that the bulbs on the left are working, other than the charging bulb.

Any thoughts?
_________________
1982 931
1986.5 Silver 928S
2008 Volvo XC90 (Daily)

Past lives (I miss them all):
2007 Hummer H3 (Timing chain guide failure)
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)

[Raize]

I think if you had no power from the ignition switch then none of the lights would work. There are two black wires, the one from Pin 7 is the one you need voltage on. The one from Pin 12 just connects to other dash instruments.

[bureau13]

I have to go look at the connector, I don't remember which pin number I was using. But I was thinking that as well, if it were really the ignition switch that can't be the only symptom. Yet everything else seems fine.

[bureau13]

Glad I didn't start ripping out the ignition switch. Sure enough, I'm getting proper voltage on pin 7, including if I measure it with the blue wire from the alternator as ground (I forget which pin that is, 11 I think). Perfect. So then I put a 9V batter across the corresponding pins on the gauge, the bulb lights up. Plug the gauge into the connector...nada. WTF?

Possibly something with the connection itself when plugged in? It seems fine, but not sure what else would cause this. I can't imagine it's a current issue, the little bulb is not much of a load and a 9V lights it up just fine.

[924RACR]

The female socket in the connector itself can get worn and not make good contact...
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Raize]

Either corrosion on the connector, the connector has expanded/worn so it doesn't make contact with the pin, or the locking tab is not engaging so the connector pushes back in to the plug instead of on to the pin when installed.

[bureau13]

I did some additional experimentation and noticed that as soon as I attached the bulb to the incoming harness connectors from alternator blue wire and the 12V from ignition, the voltage was dropping to nothing. So I came to the conclusion that the problem was at the alternator. I started unscrewing the bolts holding in the voltage regulator, since I had an older one that still worked, but before I could get it out I bumped the alternator ground strap and...it just fell apart. I'm guessing it was completely frayed, but just sort of held together by a couple strands, which wasn't enough to conduct any sort of current with a load attached. So dumb.....
_________________
1982 931
1986.5 Silver 928S
2008 Volvo XC90 (Daily)

Past lives (I miss them all):
2007 Hummer H3 (Timing chain guide failure)
2004 RX-8 (Wrecked)
1993 RX-7 (Sold)
1987 RX-7 Turbo II (Sold)
1985 RX-7 GSL (Stolen)