Alternator ? cut wire ?

[OldTee]

Found a cut wire under the left rear fender. One side went to ground the other disapeared into a wire bundle that went into the engine compartment somewhere. So, I spliced the wire back together. Ran around the block and found the gen light on pink, not the red-red when you turn on the ignation. Cut the wire and ran the engine. Light behaved normally. PO said he did not upgrade the alternator in the 20 years he owned the car. He did not know anything about a cut wire.

Any hints or explanations????

[OldTee]

de Bump. Could this wire go to the airconditioning? Since it is deinstalled, via removing the fan belt, no way to check now. The wire has a hint of yellow in it and maybe some brown.

[targa80]

what year and model do you have? That might help with figuring out what the wire is.

[OldTee]

Opps, Sorry. 79SC coupe.

[targa80]

The next question would be where in the lower left rear quarter panel is the wire? Is it close to the tail lights or close to the door frame or somewhere in the middle?

[john70t]

My post would be theoretical, as I'm terrible with electrical, so....
-the alternator dash light light works (so I've been told) by having 12v go to one side and light it up(don't know how it's grounded).
-when the alternator starts making voltage, that goes to the other side of the bulb and cancels out the flow through it.
-so if the grounded wire is taking current out of the dash bulb, the wire must be related to the charging system.

My hail-mary guess is that it's part of the alternator sensing that goes to the battery/regulator and controls field coil current for voltage regulation.
The other fat alterntor wire off the alternator is for battery return current so that's the only other function(?).

[john70t]

Fender is front, quarter panels are back BTW.

[OldTee]

It is the left rear fender well. One of the cut wires went to a ground lug about near the top of the fender seam. The other wire went into a wire bundle that headed for the engine compartment through the fender well. Other wires went to the tail light assy. When I connected the wires (see the first note) and drove around the block I had smoke come through the heater/defroster outlets. I thought at the time it was from residual oil in the heat exchangers but now I wonder if it was from something burning. I can find no chared wires yet. There are about 6 or more items connected to that ground lug. It is not an alternator problem because the car runs fine, the light works properlly etc. Thanks

[Jim Sims]

No alternator wires were originally located in the left rear wheel well (if by that you mean the area above the left rear wheel and not in the engine compartment.) It is poor practice to blindly hook up a cut wire to a brown ground wire or any other wire to see what happens; one could be making a dead short this way which could damage a lot more that just the wires being checked. Like big sections of the wiring harness which are expensive and difficult to replace. Go buy a $10 VOM or an even cheaper 12 volt test light and use these to troubleshoot. The cut wires in the left rear fender wheel may be the unused wires to the "nebel" or fog light which was an option more typically installed in Europe. When these wires were not used they were merely left trimmed, taped at the ends and secured to the rear tail light wiring harness. Cheers, Jim

[targa80]

I agree with what jim has written about those wires. Using a volt meter you can verify that there is voltage on the line with the car off and ignition on accessories then with car running. With car running check with lights on or in reverse or fog lights on. Pull a fuse and try the test again to see if the voltage is gone. this will verrify what circuit branch it is from. Be careful not to pull fuses with the car running. Shut the car off then pull a fuse then start the car. This will be a little safer way to troubleshoot and only do one at a time.

[Rot 911]

First off let's get some more details about the wires. Is the wire that went to the "ground lug" brown? How about the wire going to the wire harness? All 911 ground wires are brown, no other color, just brown. So if the wire going to the harness is not brown don't be trying to ground it out! Finally, was everything working ok before you started messing with the wire? If so, just tape the damn thing off and leave it alone. Later on if you discover something in the car that doesn't work, then do an investigation.

[kpfoten]

rear fog lamp wire?

[OldTee]

Nope. While I don't know where it goes, wherever it does it takes enough power cause the alt lite to come on whild not popping a fuse somewhere. There must be a relay somewhere in the circuit.

[Jim Sims]

Be careful! Some 911 circuits are not fused. Jim

[OldTee]

Warning heeded! Any AC guys know what the ground may be attached to? Some engine control perhaps? Long ago some work was done, ie installing a rebuilt compressor that never came on line.