Electrical bug !!!

[bohn]

I've been chasing this problems since i put my truck together and it pretty much has me baffled. So i'd appreciate and ideas on what it could be.

When i start it it only has 9 volts and very dim interior lights. Within about 30 seconds it jumps to 14 volts and lights shine nice and bright. It will stay at 14 volts for awhile and then drop down to 9 volts for awhile, then back up to 14. It even does it going down the road. I checked every ground i could find and are all good, i checked the battery, alternator and starter and everything is good.

I even ran a wire from the accessories directly to the alternator to energize it all the time and it does the same thing.

Anybody have any ideas.

[lazyass]

i was going to guess voltage regulator? not sure

[nos2go]

regulator

[jdsgallops]

Either a regulator, or underdrive pulley.

[NEW BUILD]

Start with regulator

[bohn]

On a GM isn't the voltage regulator part of the alternator. Its got the stock pulleys on it to.

[lazyass]

i don't understand how it could be a pulley, but yeah regulator is part of alt.

[nos2go]

what kind of vehicle..Im sure you can get a kit

[cevan]

i had a problem just like that last year on my pick-up, mine was the alternator, check it again

[jdsgallops]

i don't understand how it could be a pulley, but yeah regulator is part of alt.


The larger diameter pulley slows down the exciter reaction, which could cause a problem as such. My car does this all the time and didn't start to do so until I installed the alternator pulley of my underdrive kit. Still charges and starts the next morning which is all I worry about.

[lazyass]

i would think it would be more constant, not just every thirty seconds or so, dont' know

[Wasted Income]

It's obviously intermittent, and may be a function of heat from charging, engine bay heat, vibration, etc. Might be something as stupid as a broken solder joint inside the alternator. There's no doubt it's the alternator though.

[UPdragracer]

I'm not one to over think stuff so I'll just say I bet that damn belt is slipping
Try a new belt and adjust it properly .
If all that stuff is ok then the field wire to the alt might be loose at the connector at the alternator . make sure it pushes on snug {make sure the female part of the connector is tight } Good luck and let me know if I can help I could take a spin down and check it out with you :D:

[bohn]

Its got a serpintine belt so its on there tight. I will check the alternator again, the weird thing is that this is the complete set-up i ran in the bird and it never gave me this problem. It isn't consistent to every 30 seconds, sometimes it holds 14V for hours but will drop down and then jump back up. It still charges the battery, but its just annoying.

[UPdragracer]

Well I have seen some pretty messed up instrument clusters also it might just be the gauge . Have you tested the actual voltage coming out of the alternator ?

[bohn]

yes i tested it with a volt meter, i'll take the alternator off and have it tested again. If you get down this way to pick up those parts UPdragracer, maybe you can take a look at it if i don't have it completely apart by then.

[abot316]

what about all the grounds?

[Slow Ride]

battery?

I wrecked 3 alternators and did all kinds on trouble shooting only to find a broken plate in the battery was shorting out intermittently. New battery no more problems

[bohn]

I'm gonna go back over the grounds probaly this weekend if i get time. The battery was new this summer, and i also ran that in the bird, thats why i think its in the wiring somewhere. Maybe i'll just swap out the engine harness (it only takes a few minutes) and see what happens.

Its pretty much down for the winter anyways so i can get the body and suspension down for next year.

[UPdragracer]

what about all the grounds?

Good point those chevys have a bunch of those damn grounds attached to the cylinder heads. I have also seen those hanging on by one strand of wire causing an intermittent problem :chnsw: