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Lights dim intermittently at higher rpm

1K views 6 replies 6 participants last post by  schwim 
#1 · (Edited)
Hi there guys!

79
New alt, reg and batt

Drove it tonight and lights began to dim intermittently at 2000 rpm and higher, putting the clutch in and allowing it to return to idle would cause it to stop dimming.

All lights internal and headlamps dim. Headlamps are feeding through relays directly off of the battery so switch feed is not the culprit.

Alt light came on once for just a brief moment then went back out. It illuminates when switched to on so bulb is not burnt.

Most likely culprit? It sounds like a regulator but the alt light makes me wonder.

Thanks for your time!

 
#2 ·
Are you grounded good?

Another thing a friend had trouble with, although not the same symptoms, was his dimmer switch, even though it was fairly new. But, I don't know if that would apply since you have a HD headlight wiring system.

Just thinking out loud, hope you can figure it out!
 
#6 ·
Can you replicate the problem sitting in park in the driveway with the hood up?
I'd rev it and see if the belt is slipping, they can occasionally slip with no sound, its possible you can actually see the slip
I'd hook up a meter, rev it, and watch and see if the output to battery (or straight off alternator) drops
the regulator's job is to 'shunt' and excess electricity when its rev'd
If you hook up meter straight off alt, when the lights dim you will see alt output drop or possibly not
That should divide the problem in half right there

From there on, bad connection, bad regulator, so many possibilities
 
#7 ·
Hi there guys,

I woke up this morning and put my voltmeter on the battery. During rev, voltage would go from 14.2 to 12.4-13.1, etc. I rooted around in the trash and grabbed the old regulator (since it's easiest to replace) and plugged it in. Voltage stayed at or above 14.2.

I went to Carquest and they gave me a replacement(BWD R400). I think I remember having a failure problem from new with this particular brand twice before. If I'm right, that's the third BWD regulator that has been a non-operable or faulty part from new.

I haven't installed the new BWD regulator yet. The old regulator has been through three alternators now so I want to swap it but I may see if I can get a FoMoCo replacement on Amazon or eBay.
 
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