chances are its not your alternator.

I will post a link to a thread when I was having charging issues. If it isnt the grid heaters than it is a wiring issue.
Most alternators are grounded internally which doest do it sometimes when grounds arent the greatest. Most times alternators have a post where you can do an external ground. So I like to ground them to that and make a ground post on the wheel well or frame (or find a good existing ground post).
alot of times a 112-16 gauge wire is used. I prefer a 8 or lower. Also, because you have an amp gauge that is in series with your amp and battery. So if you had a loose connecting it could make this happen.

 

Interesting...

So what kind of symptoms were you seeing?

The other day, I was having some issues - low voltage on the guage and the check guages light was on. Got back home and checked votage - definitely was low. Charged batteries, and started it back up yesterday. It wasnt even showing 12V. Seems pretty clear that its the alternator but youve got me second guessing myself.

To my knowledge this is the original alternator in a 11 year old truck.

 

and an FYI most of the alternators made in the last 10 or so years are solid state and dont have brushes.

like I said after doing lots of reading on alternators 9 times out of ten the alternator is fine.

 

Thanks Bill - excellent info

A foot of wire is a cheap fix eh?

 

yeah to rule out your alternator or at least see if it might be the problem is take two wires(the bigger the better) and put one on the battery + terminal and then touch it to the alt + with your meter on the battery + and -. If the batttery voltage goes up when the wire is touched to the alt then you have a wiring issue on the + side. Do the same with the Ground and watch the voltage. and that would rule out that side. I actually had a + and - wiring issue and found it by doing both wires. Test of course must bee done when truck is running and warmed up

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and if nothing shows up there and you can remove the alternator quickly and there is a parts store close it doesnt hurt anything to get it tested.

make sure you unhook the battery or you will blow the fusable link (I know from experience) if the positive cable hits the alt case.

 

Thats funny,the last two that I worked on had brushes,I don't know what 9 out of 10 have in them,but I can tell you for a FACT that the last two times I had the problem that is described above I pulled the alternators and BOTH times the brushes were bad.
Go ahead and pull the batteries and replace em' for $75 bucks a piece,then screw around with changing the wiring all around,then once you've done all that then try what I said,I could have just had the same thing happen to TWO DIFFERENT trucks and got lucky and BOTH times the unimaginable happened.

 

The rectifier is made up of a bank of solid state diodes. Still requires brushes to operate though. Is that what you mean?

 

Okay,bear with me,I'm not an electrical genius so all I can do is describe what I did.
Hell,I'll take a picture,I have a spare alternator...

 

Sorry Krabs I was agreeing with you, that was meant towards GRI. I should have quoted

 

Unwad your panties....(Is that why they call you Krabs???..... )