Bad 3g alternator?

[rhkcommander]

Hey guys,

Not sure if my alternator regulator is shot or not, I upgraded to a 3g a while ago.

I installed a volt meter (along with oil pressure and coolant temperature), truck has been getting harder to start lately. Voltage at all speeds is about 13V, doesn't seem to go up with RPM. The gauge is analogue and my electric pump makes the needle jump quickly... (side question, any way to fix that issue?). When hitting the glow plugs it dives down to high 10s, cranking with them on to low 10s.

If I turn on the blower, wipers, headlights each will cause voltage to drop.

The belt squealed the other day when I revved it after cold starting, so I'm assuming it was trying to generate.

All of the contacts should be clean and tight but I will triple check. I use a 150a re-settable fuse on the lead, with the smaller wire tied into the fuses post to pick up voltage.

Thanks for any advice.

 

[Macrobb]

Pull the alternator and have it tested - really quick, free. I've pulled one from the parking lot at autozone, taken it in and had it tested, then reinstalled.

If it tests OK, go over the wiring. Then, new regulator(I've had a 'good' test with a 'iffy' regulator)

 

[genscripter]

I agree you need it tested by an auto store to ensure a proper diagnosis.

However, I don't trust auto parts stores anymore. If some pimply teenage wallflower tests your alternator, you might want to have it tested elsewhere. They are notorious for incorrectly testing them.

Once at a Pep Boys, I had a teenage clerk "test" my alternator twice and both were "bad." I watched him set up the machine wrong, and claimed he was doing it wrong. He insisted he was doing it right.

I relented and asked for a new alternator. He thought I was going to just buy the alternator, respecting his diagnosis. He went back, brought a box off the shelf, and opened it up. He started ringing it up, and I said, "test this one." He assured me its new, and it will work. I insisted he test it first. Annoyed, he took the brand new alternator to the machine and hooked it up wrong. The machine stated it was "bad." He retested it again. "Bad."

He didn't want to admit it, but he didn't know how to use the machine and as far as I could tell, he was testing all the alternators wrong, giving false results to everyone.

 

[rhkcommander]

Will do, thanks for the infformation! I will pull it in the morning

 

[crash-harris]

IIRC, the test harness for the 3G is N-07 with the machines autozone uses.

What kind of "resettable fuse" are you using and can you get a picture? I was using a breaker and if may have been the reason for killing 2 alternators in a many weeks.

You do have the green wire on the harness connected to the green/red stripe wire on the truck, correct? Battery light bulb isn't burnt out?

 

[rhkcommander]

I have a 150 amp breaker, green wire to red n green ignition wire, yellow hooked to positive post on alternator.

Cables arent hot from charging, belt squeals when i idle rev it cold n sitting. Not loose though.

I will pull it when i get a chance. I installed a volt gauge and get 13 cruising, every feature i turn on drops it under

 

[crash-harris]

My old belt seemed tight, but had more to go before it actually stopped squealing. That was just a bandaid until I could get a new one, which helped. If it's still squealing with the belt as tight as it will go out a new belt, then it may be bearing squeal.

 

[rhkcommander]

New belt, i can deflect it a little with a lot of pressure, i will crank it again and see. I might be able to get a little more. Ive been tempted to find a way to do double belts on it if possible.

I charged the batts up today on 40a setting until it kicked off, still only 13v when started. Wouldnt the alt go higher even if it slipped? I will try direct wiring wihout the breaker, then automotive alt test if that doesnt work.

Ive swapped regulators in the older 3g, piece of cake if thats the only other possibility.

Thanks all for the advice

 

[crash-harris]

Take the breaker out of the equation by putting both cables on the same breaker stud. I did the same thing, pulled my less than a month old alternator off in the AZ parking lot and tested it. It failed all 3 tests. I tested a new reman off the shelf to insure it was good and used the electric impact in the store to swap the pulleys out and tossed the new one in. No issues yet and I've left the breaker out of the loop for now. I'll replace it with a 200A mega fuse when I can.

 

[laserjock]

Second on bypass the breaker and check with a different meter. Gauges can lie to you. My overhead gauge says I’m running really hot (over 15 volts) but dmm on the battery says 14.6-14.7 when it’s charging.