Troubleshooting Alternator!!!, don't know the next step!! Options

[porsha916]

the car is a 1973, the engine we just installed is a 75 1.8 with carb, the red alt warning light is on when engine is reved up, at idle light is out or on, but very dim.When engine is reved up, voltage gauge goes up to 16, if I turn everything on the voltage drops to about 14, but the alt (red) light remains on. I have changed the voltage regulator with about four other used ones, no change. Is the wiring on the circuit board or alt different for different years. I need help!!!!!
Thanks
Bill

[bd1308]

should be the same for all years....something is toast....

i would say the VR, but since you replaced that....wait, used ones? Get a brand spanking new one and see if it doesn't change anything...the OE type VR is a mechanical one (i think) uses latches and what-not to regulate voltage. the magic smoke goes away after awhile and you have a paperweight left.

I'd check the diodes....or even maybe the brushes, but that would not make it run up to 16V....


got me....

b

[Dave_Darling]

I would check the wiring going to the alternator, and check the relay board. Usually, when alternators die they won't put out enough voltage. When VRs go, they can let the alternator put out too much voltage--so your symptom is much more likely to indicate a bad VR than a bad alternator.

Having some specific wiring problems may also be able to cause this symptom. So I'd check the wiring next. And then buy a brand-new VR and see if that helps.

If not, I guess it would be alternator replacement time. Or at least time to have it tested at a shop.

Remember to wash down the battery tray and suspension console area with a baking soda and water solution; you're probably causing the battery to puke acid every time the voltage goes up to 16V.

--DD

[Dr. Roger]

Ebay self regulating 100A alternator and a custom made bracket.

It works and alt runs <$100.00.

[brp914]

rank speculation, but I'll give it a try. It seems unlikely that 4 VR's would be bad. Also, 14 - 16V under load makes it seem Alt is ok. I just went thru a bunch of #@^% where the alt light would come on that ultimately had nothing to do with the charging system. There is a bunch of stuff that runs thru fuse 9 (check if blown). A short in any of that stuff and the alt light will come on. Hopefully you're handy with a voltmeter and circuit diagram and can track it down if it comes to that.

Still, I would pull the alt and have your flaps check it. While its out, check that the alt cover plate isn't causing shorts. Also the harness where it goes thru the engine tin - I had a meltdown there once. I'd get a new VR to have as a reference. good luck