My alternator won't charge unless I jump it from the battery the only lights in my dash that work are high beam, and over drive. My temp gauge only works when I'm in over drive. Any ideas?? I haven't tried anything yet, I did install a new radio a while back. I've tested all fuses fyi. Thanks

 

did all those things work before the stereo install?

 

They didn't just suddely stop they stopped about three weeks after Install??

 

Can you recall when this happened and did everything fail at once . Also what wires were moved around during the stereo installation. How good is the battery.

 

Sounds like the circuit board of the instrument cluster went bad which happens often at this age, and all kinds of crazy things can happen. I'd refloat ALL solder points on the back of the board, see what happens.

 

I re sodered the points it didn't do anything

 

the 91/92 740/940 instrument cluster is problematic, and not directly replacable with any other year. my 92 had speedometer problems and even re-capping it didn't help, my guess is, the ITT 2015 speedometer chip was flakey.

but thats not your problem. I'd check out the ground block thats left of the drivers footwell and just forward of the door hinges, at the bottom. make sure every connection is good.

I'd also check the red wires from the 'positive terminal' to the ignition switch... on a 7/940, the positive terminal is on the firewall above the pedals, its a flat black box about the size of a box of chiclets, with a whole bunch of red wires attached... the plastic lid unsnaps...

for the alternator to start working, it needs juice on D+ to bootstrap the field coil... the ignition key supplies power when its in II or III to the batt/alt bulb in the instrument panel, then this bulb is connected to D+ via a thin wire. If its working, when you turn the key to II, the alt light comes on, indicating that bootstrap current is flowing, then when the engine starts and the alternator is generating power, the light goes out