Generator light with key off

xgregx

Member
Hello all,
I recently brought home a 66 Wildcat convertible with the accessories, intake, and one head in the trunk from the previous owner who started to pull the engine.
I decided to test the electrical so I got a new battery and connected it to the positive lead, and grounded it by bolting the negative lead to the block.
Electrical started to work, and I could run the lights, power windows, blinkers, heater motor etc. Even the 'cold' and 'oil' lights came on when the key was on.
I disconnected the battery before leaving it.
Today I reconnected the battery to test the courtesy lights and now the 'generator' light comes on when I connect the battery and I'm not getting any power. So the lights, blower etc that worked before don't go on. Cold and oil lights do come on when the key is turned. Starter still turns.
Keep in mind, the alternator is out, along with all other accessories/brackets and the normal grounding mount for the battery on the power steering bracket.
Based on my research, the generator light goes on when there is a bad diode (which I think is not the case since the alt is removed). It could also be the voltage regulator. Anybody know what this issue might be? Should I not even bother to worry about it until I have the alternator back in?
I would like to be able to work on electrical stuff while the engine is out and figured grounding the battery to the frame would allow me to do that.
Maybe something shorted and I messed up the voltage reg?
Thanks!
Greg
 
Hey Junkman - It is an alternator. Thanks for the reply. Yeah maybe there was a loose wire somewhere that shorted and burned up the regulator. Previous owner disconnected lots of stuff, I'm still learning my way around things.
Greg
 
Since it is an alternator, then this makes this a lot easier to diagnose, in the sense that almost all GM alternators of that vintage use the same voltage regulator. I suggest that if you have a local electrical repair shop nearby, you should take the alternator and the regulator to them, and have them test the alternator for any bad diodes. DO NOT swap it at a local auto parts store, because generally speaking, they are not quality rebuilds. If you want to keep your Buick as-built, then have the original alternator repaired. Check the date code and the part number on the alternator to determine if it is original to the car. I prefer to find NOS electrical components because some of the junk that is coming from overseas is worse than an original part that you would take off a car in the salvage yard. I many times will use a junkyard part when a NOS part isn't available because every car runs on used parts. The factory service manual is the best advice that you can find quickly. When that fails, then ask on the forums. Solutions to complex problems are not complex to the elderly that grew up with these cars. My first Buick was a used 1926 Buick Master Country Club Coupe, Model 54C
 
Hey Junkman,
I don't think the alternator on there is original but I'll double check. The alternator isn't in play here though. It was never on the car when I got it. Previous owner had taken the accessories off. Alternator was in the trunk when I got it. I wired a new battery to the positive junction terminal and the negative to a head bolt just to test the electrical as the engine is non-running. At first everything worked, but later the generator light would come on when I would connect the battery. Again, alternator is still not in the car. I was mainly wondering if the light was a false-positive due the alternator being removed, but I was a bit confused why I lost power to the lights/windows/wipers etc after they were working the first time I hooked up the battery. I was hoping I didn't fry something. Something else to add to the to-do list. Thanks for the advice. I like the have most parts rebuild if I can.
Greg
 
Greg,
From the symptoms described, it sounds like the ground to the body and front end sheet metal was lost between the first test session and the second. The now inoperative loads depend on having a ground path back to the NEG battery terminal. The original negative battery cable has a short #14 gauge stinger that goes from the battery connector to a sheet metal screw fastened near the battery tray. See attached page from the Chassis Service Manual.

This #14 wire carries the ground current from the body and front end sheet metal back to the battery for the loads not mounted on the engine or transmission. With all the vibration isolators on the body, there may not be an electrical connection between the body and frame. Or the previous owner may have taken off any jumpers for that purpose.

The starter, OIL light, and COLD light still worked later because their ground is through metal of the engine and the #2 gauge heavy negative cable. Hopefully nothing is damaged from the testing. The voltage regulator has no solid-state components to get zapped.

Trying to analyze the behavior of the GEN light at this point becomes very complex if there are missing grounds or other disconnected wiring. I would say for now restore the cables, grounds, etc to the factory set up as far as possible, then worry about what the GEN light is doing.
 

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Hi Todd,
Yes - that was it. Body ground came off. I knew it had to be something simple. Wire going from an inner fender bolt was hanging loose. I grounded it and things went back to working.
Thanks for the help!
Greg
 
The positive battery cable gets connected to the junction block & everything is then picked up from there.
Looking at the wiring diagram posted you can see this. SO there has to be a problem at the junction block.

Tom T.
 
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