The car is a 1972 Olds 442 with Externally regulated Alternator. Was driving at night time, with headlights on. Heard a loud POP from the fire wall, and immediately after the pop, the red GEN generator light came on, and all the headlights and instrument/Gage lights lost about half of their power. Good news is that I was 3 miles from the house, so drove it home.

Sunday I go to trouble shoot. Red GEN light is still on. Checked the alternator, and it appeared to be OK. Replaced the firewall mounted voltage regulator with a spare one from the shelf, and the red GEN light finally went away.

Took apart the voltage regulator, and found that the yellow wire was burned as you can see in this photo. Looks like it was damaged by some sort of an extreme voltage spike.

So what is the root cause here? Anyone knows what would cause this yellow wire to melt like this?

How do I test to make sure the new Voltage Regulator won't have the same problem?

 

I don't know the answer, but lets move it to the top and see if someone else can help you! John

 

Looks like something shorted in the regulator, an alternator will not make much more than 18 volts unregulated.
Use a multimeter to check the voltage across the battery, it should be about 12 volts before you start the engine and 13.5-15 volts with the engine running. while the engine is running turn on all the electric services (lights, fan, rear window defogger etc) and the voltage should remain stable if the regulator is doing its job properly.
Regulators can fail at any time, however there isn't much you can do to see if it's about to fail, they normally either work or not.
It could have been much worse - you didn't have an electrical fire which in a worst case scenario might have destroyed the car.

 

What rusty said. If you have another regulator failure, have your alternator checked for a bad diode.

 

If the new reg is a lightweight solid state one, it will be built differently and will not have that same failure mode.
Of course, any regulator or other electrical part may fail at any time.
It is possible that the connection of that yellow wire was getting weaker and weaker until the current flow finally opened it.
Do the voltage chaecks above and if it all appears normal, continue driving. It is also a good idea to have an extra regulator in the trunk, just in case something like this happens again, whether tomorrow or 30 years later...

 

Ali,

Long time no see.

My guess is one of the coils inside the unit overheated and went south, taking the wire with it. If the new one works good, sounds like no major damage was done anywhere else, like to the alternator itself. Might want to run it up to O'Reillys and have them check the output on it, just to be sure tho.

You coming down for the BOP drags?

C.J.
STILL working on the Cutlass!

 

I'd be interested in getting one of these solid state. Do you have a p/n or a source for one?

 

Remember that a new one will probably be of Chinese manufacture, while an old one, such as one from a parts car, will probably be American made and of higher quality. If you buy a new solid state regulator, I'd recommend carrying a used mechanical one as well, just in case.

- Eric

 

You can also go with an internally regulated GM alternator like a 12SI case and get rid of the external regulator see this link I did it and haven't had trouble since especially needed the extra amperage because I run An aftermarket Stereo and CD ignition system I run a Summit racing Black powder coated 100 amp 12si case alternator

http://www.rowand.net/shop/tech/Exte...Alternator.htm

 

I do not know a particular source of solid state regs as I got mine from a hole-in-the-wall aleternator shop out in the boonies.

I heard that napa or advance may have them. Easy way to tell is by weight. The solid state one will feel much like an empty housing when compared to the mechy one...

 

thats what I want to do I checked it out not sure I follow it maybe Im to tired
Tony

 

How much the same is the buick? I have a 66 cutlass no air
Tony

 

ther are 2 differend voltage regulator's internal and external regulation as do the alternators.
in my chassis manual 1969 it say's that only the 442 had transistorized alternators? and like mine 69 delta 88 had external regulators.

so refering to my question, external alternator with internal voltage regulator and vice versa?