Strange voltage issue

[Roustabout]

Hi

I have recently replaced my battery and had my alternator rebuilt by a reputable guy that has done good work for me in the past.

The last two mornings were pretty chilly. Yesterday morning I fired up the truck and noticed that the battery light stayed illuminated. The voltage was showing 11.5 on the scangauge. I shut if off and immediately fired it back up and the everything appeared fine - no battery light and scangauge showing 14v.

This morning I verified the battery voltage before firing up the truck with a multimeter - 12.5v - no problem. I then fired it up and bingo - battery light and scangauge showing 11.5v. I read the voltage at the alternator and battery with a multimeter while idling and got 11.5v. Switched the truck off and re-started and everything read 14v again.

Any ideas? Does the voltage regulator in the alternator have any moving parts that could stick in the cold? The serpentine belt is relatively new and I didn't notice any slippage.

Thanks

 

[crown14]

Check battery connections

 

[antichrist]

Sounds like the exciter circuit for the alternator is being flaky. I don't know if it feeds though the ignition switch or not, but I'd think it would.

 

[messar]

check the ground wire from the battery to the tie in point.

 

[Roustabout]

Thanks guys

I will check the ground and battery connections one more time. I did notice that the smaller yellow wire on the alternator looks like it had a different connector spliced onto it. Does this wire feed the rotor coil?

 

[Roustabout]

Update:
Checked all of the alternator connections and grounding points as well as the battery connections. All were clean and tight except for the the battery ground connection - the clamping bolt was tight but the clamp was worn so that it didn't grab the battery post tightly.

Always best to check the obvious things first. We'll see if that did the trick - tomorrow morning will be cold.

Thanks again for the suggestions

 

[Roustabout]

Update:

This morning was the coldest morning so far this season and I saw the same issue when starting the truck. I tried this suggestion:

"Next time it does it give the engine a little rev... i have seen regulators not kick in until a certain rpm or voltage was seen,,,mite be a glitchy reg or sticky brush"

Blipped the throttle and the voltage snapped back to where it should be. I guess I'll throw in my spare alternator and take the rebuild unit back to have it checked out.

Thanks again for the suggestions:cheers: