techartisan

84' 944
So last night I went to leave work....I knew something was wrong as soon as I opened my car door. Door chime sounded and the alternator light was illuminated. I tried starting it with no luck.

Im headed to where the car is to try to figure this out. I searched the forum but havent found this particular problem listed anywhere. Im thinking ignition switch maybe? I have a spare so Ill try that first. But if its not that....what else would it be? Is there a mode of failure that would have a bad alternator turn on the light without the key in the ignition? Ive got an hour by bus to think about it...so Ill be checking for tips on my way.

Thanks

Van

Hmm... when you turn the key on, all the "idiot" lights come on as a sort of diagnostic. This should include oil pressure, alternator, coolant temp, etc. Do these other lights turn on when you turn the key?

If I recall how an alternator works, there is the "field" wire, that's blue. When the ignition is on, this wire gets 12v - this wire actually comes through the idiot light bulb. When the alternator is not charging, this circuit is completed by connecting to the car's ground and the light turns on. Once the alternator is making power, this blue wire is no longer going to ground, but rather 12v - there is no voltage differential now, so the idiot light doesn't turn on.

You might have to find the wiring diagram and find out how that's switched...

But, if, when the switch is off, the instruments/lights are grounded; and if the blue wire is somehow touching the large power wire that connects the alternator to the positive battery terminal, then you'd be getting a voltage differential - even with the ignition off - and that might make the light glow.

techartisan

when I try to start everything seems normal except its not starting.

when I got to the car today, I hooked the battery back up and the seatbelt light and alternator light were illuminated. I noticed the drain on my battery compartment was clogged and there was a couple of inches of water, so I cleared it and let the water drain. This is an early 944 so the water on DME issue does not apply here.

I tried to start the car with no luck...but the battery light/seatbelt light/door alert arent turning on without the key in now. Im not sure if it was related to the water or not.

I swapped by ignition switch with my spare to make sure it wasnt the switch causing my "no start". Seemed like a fair guess given the inappropriately timed alternator light/seat belt/door alert. This did nothing to help though. I swapped in my dme relay bypass....I can hear the fuel pump...cracked open the fuel rail and confirmed fuel...though I was unable to test pressure.

My alternator was bench tested a few months ago when I had a charging issue that turned out to be a loose exciter wire.....but even without the alternator charging the car started then....so I really dont think its the issue.

Ran out of light before I could test for spark....and my multimeters battery was dead when I got there so I couldnt test the batteries charge either. I cant make it to the car tomorrow so it will have a day to hopefully dry out and decide to run. Right now its parked on a hilly road with a soft shoulder that drops off about 30 feet so not the ideal place to try to sort this out. If I cant get it started monday Ill have it towed to my work.

Van

When you say "it won't start" - can you be more specific? Does the engine crank over? If it does crank over, is the camshaft turning (broken timing belt??)? If it does turn over, can you smell fuel in the tail pipe? If it doesn't turn over, does it make a click? Did you try a jump with another battery?

techartisan

Turns over but doesnt fire up.
I didnt bother to check the T belt.....the lights/door chime issue has me convinced its electrical in nature. My previous owner was pretty creative in his care of the wiring...so I have always had electrical gremlins...But the door chime/alternator light with no key is a new one by me.

Tomorrow, if it doesnt fire up after having sat a couple of days Ill check for spark. Try to jump it. If that fails Ill swap my spare computer in. After that Ill have to have it towed down the hill to my work so I can get it up on jacks to check the wiring from battery to starter to alternator.

My car is a bit hydrophobic. It likes to stall on not so large puddles....Ive been living in the desert from the time I bought it till now so it was a rare and easy to ignore problem....Portland may be the encouragement I need to seal up the electrical from moisture.

techartisan

Well I hate to leave a thread without resolve....but this is all still a mystery.
I went today....wouldnt start...wouldnt jump start. So I started rolling down the hill....a tow truck wouldnt have been able to turn around on the road I was parked on. As I went down I tried to "push start" it a few times. 3rd time it fired up....drove to the bottom...turned around and drove back up. Killed it....restarted fine. Returned the rental.
Got back to my car and it wouldnt start AGAIN. Turned over fine just wouldnt start. While trying there were a couple of loud pops....didnt sound like a backfire....not sure what it was. Finally I decide to roll back down the hill....and try the "push start" again. AND the engine started...but the rpms were sub500 and any pressure on the gas stalled it....but as I was coasting down a huge hill I was able to "push start" it back.....When I got to the bottom of the hill I popped the hood:

pulled an injector lead....no change.
wiggled the afm wires...no change.
wiggled the afm....and suddenly...the engine woke up. I tightened the AFMs connections....drove to work....later drove home....a trip to the grocery.

Everything seems fine. The lights without keys fault isnt happening. Its running fine. Starting fine.

I was supposed to install new axles and wheel bearings last weekend....
I think my car was just nervous...took the weekend off

Ive no better explanation at this point.