Voltage drops when hitting bumps???

[ComancheKid45]

Alright ive been chasing this issue and will continue to do so but figured Id see if I could find anything new about it here. This is my 88 4.0l AW4.

 

What ive got here is at night with headlights and driving lights on whenever i hit a bump while off the gas my voltage gauge (which isnt really accurate to start with) drops all but into the red for a second or 2 then revives itself back to normal, all my lights dim at that time as well. If I'm on the gas going down the road it doesnt phase it, its just when RPMs are low. Ive tested votage at the battery with every single load i could put on it and I get a reading of app. 12.6v at the posts. With just headlights and driving lights i get 13.7v so the Alternator is doing its job fine, however I havent seen what it drops to when i hit bumps with a load on the alternator. My ground cable is in good shape and the terminal is tight on the battery, I'm going to rechack everything here today but was wondering if theres a regulator or something that could be going bad or knocked loose somewhere.

 

Ill post up if i come across anything else, and thanks for any help :hmm: ;)

[mkbruin]

Serpentine belt loose?

[jimoshel]

My money is on a intermittent short in the light wiring. Rare but has happened is a loose plate in the battery. Generally one of the posts. With a load on the battery , motor off, tap, wiggle each of the battery posts.

[flyn2er]

How about the wire connection inside the alternator?

[ComancheKid45]

Alternator is a new 1 installed last spring. I drove it this evening and it only managed to drop on me 1 time throughout a decent trip in the mountains.....idk excatly what it is but i might look into upgrading the headlight harness in the future. For now both terminals and cable are tight and in good shape and it does its job so we'll see what comes of it. :thumbsup:

[Automan2164]

Alternator is a new 1 installed last spring. I drove it this evening and it only managed to drop on me 1 time throughout a decent trip in the mountains.....idk excatly what it is but i might look into upgrading the headlight harness in the future. For now both terminals and cable are tight and in good shape and it does its job so we'll see what comes of it. :thumbsup:

 

How's the chassis ground?

 

Rob L.

[ComancheKid45]

The ground behind the tail light was clean a few months ago when i checked it, i will pop the light out and check it again. the ground to the engine is clean and tight as well.