I just picked up a 1995 sunfire in a trade and I can't figure out the problem with it, other than the previous owner. The voltage regulator was fried in the alternator so I went to pick and pull and installed it. The previous owner wired up a wire to the ignition fuse with a switch to tell the alternator to start charging, and when its hooked up, it works great, but when the original engine harness is all thats hooked up, the battery light stays on and the car doesn't charge. Is there a way to bypass the engine harness and go straight to the ecu to check whether its a harness problem or an ecu problem? I've got another harness, but i don't wanna pull the whole thing just to find out I have to track down another ECU as well....

There's a bulb check wire and an ignition wire. You can get new harnesses for cheap that solder on. The regulator wire should power up with the ignition. If not start checking fuses.




Your car may do 13 sec @ 103 mph, but my car does 146db @ 35 hz.

The ignition wire is the one thats hacked up, but the fuses are all good, this car is just a hell of a mess, was just hoping for a temp fix to see if i needed to pick up an ecu when i go to the yard.

I'm trying to think where the ignition wire comes off of... let me get back to you on that because I'm not 100 percent sure that wire goes to the ecu. the bulb check wire does though because it feeds back as serial data to the gauge cluster.




Your car may do 13 sec @ 103 mph, but my car does 146db @ 35 hz.

If I wasn't on my phone, I would give you the url.

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Cavalier wiring diagrams

Its everything from the hayes manual. Hope it helps.