bccan

70 Cutlass, External Regulator (electronic)

Started car this morning to find "GEN" light illuminated on dash, checked voltage, not charging. Drove it to work as I didn't have time to screw w/ it. Full fielded alternator, voltage rose, seemed not entirely up to snuff (didn't load heavily) but figured the battery was drawn down a bit so voltage was a little low ( high 13's). Called NAPA, got a new, mechanical regulator, GEN still lit, would go out & charge when rpm brought up but started making a buzzing noise. "GEN" would come back on once back @ idle, buzzing would disappear or might have just quieted down.

I grabbed a spare (new 63A) alternator & swapped it in, same thing as above except when I full fielded the new alt it loaded noticeably more. So for hahas I tried another new regulator, light stayed lit full time, did not charge @ higher rpm. Swapped other new reg in, same thing. Put original electronic reg in & it charged, but unregulated like it was full fielded.

I checked wires, see no physical issues. Checked continuity - all good, though ground wire on reg connector was measuring 16 ohms. Blue wire on reg connector is grounded w/ key off, red wire has power w/ key off.

Any ideas or guidance?

bccan

Bump - I'm embarrassed to say I am stumped & hope someone can give me a direction that will save a whole bunch o' searching.

defiant1

Try a separate hard ground wire to the regulator and see if the GEN light goes off...

Does the GEN light stay on with the key off?

Wish I had clear cut answer for you.

MDchanic

I am NOT an expert on charging systems, though I could learn a bit more if I studied the schematics.
That being said, I would recommend isolating the components.
First, the alternators, either by installing each one with NO connections, or by taking them to a chain auto parts store that has a test rig. Spin them, full-field them, and measure the voltage. If they're good, then connect the wiring, and take measurements and full-field it from the regulator connector - that will prove the wiring good. If there's a problem, try it again with the battery disconnected. Sometimes measuring continuity with a meter can be misleading, because you aren't using the actual plugs the way they are connected in practice, and you miss a weak point.

Finally, if you're REALLY desperate, follow the troubleshooting steps in the CSM - they'll isolate the problem!

- Eric

Rickman48

I had weird problems w/a '69 442 - turned out the ground straps to the valve covers from the firewall weren't connected from the previous owner, causing the positive cable to corrode internally!
Check all your grounds - could be the problem.

stellar

See if the power to the red wire at the reg plug is equal to the battery voltage. You may have a high resistance connection to that wire causing an over charge with solid state reg. I will pm you with other options.