Lights/Dash lights/Alternator flicker under load

[billschroeder5842]

I have a funny things happening to my '69 electrical system.

My alternator gauge seems to be hopping around (on the positive side) with the lights on and under load--anything above 1500 rpms. Also, the lights flicker on the dash to match the alternator gauge hop.

When the car is idling, the alternator gauge stays steady, slightly positive and the lights stay consistant. I have an electronic ignition and the alternator and battery are newer. Funny, but when I apply the brake, everything return to "normal."

Is my regulator toast? Any way to check before getting a new one?

Full disclosure... I was working on it a lot this weekend so plenty of doors open, engine starts, stops and a wacky tachometer wiring issue. Could the battery just be drained a bit?

Thoughts?? Thanks!

[elacruze]

These are always tough to diagnose over the phone so to speak.

If you have a digital multimeter, check to see that you have no voltage drop from the alternator housing, engine block, and body at the ignition module mounting point. Have a helper and test whether these readings change when you apply the brakes. If you find more than 1/2 volt difference, you have ground issues that need to be corrected.

Even so, there is no guarantee that ground will be the only issue.

[billschroeder5842]

Okay will do-thnkad for the suggestion.

Is there anything else I shoudl check--the commet stuff like switches or something?

This just started happening after I was trying ot rig up my tachometer (I'm going to scrap that project and tell myslf that I need the factory look!) and some of the wiring got messed up (grounding issues)

Thanks!