Alternator question.

[JohnQ]

Originally posted in the 60 forum but thought I might get more response here-


Recently I purchased a reman alternator from Rock Auto. It seemed to work ok for a couple of days and then I was driving one morning and noticed the voltmeter reading very low.
I took the reman alternator and the stock alternator to the local parts place and had them tested. The guy there said both failed the "light circuit test" and he had no idea what that meant.
I found a shop nearby this morning that will sell me a new voltage regulator and brushes for $28. Which sounds good but I'm curious what the "light circuit test" is and whether or not a new regulator and brushes will fix the problem. I'm trying to remember if the battery warning light illuminated when starting the truck in the past. It does not illuminate now when starting the truck. I switched bulbs with the high beam indicator so I know the bulb is not blown.

Any ideas?

Also-The battery in the truck was old so I replaced it a day or so ago. I also redid the ground to the block and check the ground to frame. The truck is stock with no electrical add ons. Fusible link seems to be fine.

 

[GLTHFJ60]

So your problem is that "the voltmeter reads very low"? What exactly is it reading? When does it read low? What electrical components are on when the voltmeter reads low?

Do your brake or battery lights ever come on while driving?


Keep in mind that the stock 60 alt puts out a whopping 55 amps, so it doesn't take many extra circuits to consume that power.

 

[JohnQ]

The day the voltmeter began reading low it didn't leave me stranded and I was able to get to work but after getting there and shutting it off it wouldn't start anymore that day. I had to get a jump that evening and made it home about 18 miles away but lights were dim (only electrical I had running, no radio, a/c, or heat, etc.) and once I got it home it died.

ETA- neither battery or brake light never came on.

 

[krzyabncanuck]

Battery is to start your rig. It should be needed after that as your alternator should run everything after it starts. I say should on these older ones. I would take the alternator to a shop just for them and have them rebuilt. Right now you are just running off your new battery.

 

[JohnQ]

Battery is to start your rig. It should be needed after that as your alternator should run everything after it starts. I say should on these older ones. I would take the alternator to a shop just for them and have them rebuilt. Right now you are just running off your new battery.

It's just sitting in the driveway right now. I've not run the truck off the new battery because I knew the alternator wasn't charging the battery and I don't want to ruin the battery. I've taken the reman'd alternator off and can send it back for a replacement. While I'm waiting for the replacement I thought about picking up the brushes and regulator to rebuild the stock alt.

I should say both alternators were tested out of the truck and on the bench at the parts store. I can't find anything to tell me what "light circuit fail" (which is what the bench test said) means and the guy at the parts store didn't know what it meant either.

 

[kulangot]

Take it back to Rock Auto! Call them up and ask for RA - they might send you another one right away or they might ask you to pay for another one and get a refund when they get that one.

Electrical components live a long happy life or they fail out of the box.

(edit) your reply came at the same time as mine.

Smart, send it back. They should make good on it.

Not a bad idea to have a good spare if you want to get it up running with a local fix.

 

[GLTHFJ60]

The day the voltmeter began reading low it didn't leave me stranded and I was able to get to work but after getting there and shutting it off it wouldn't start anymore that day. I had to get a jump that evening and made it home about 18 miles away but lights were dim (only electrical I had running, no radio, a/c, or heat, etc.) and once I got it home it died.

ETA- neither battery or brake light never came on.

What do you mean by "the voltmeter began reading low"? That gauge has numbers. What exactly were you running at?

I'm with Darin, take your alternator to someone who knows how to test it. Whoever you talked to at the parts store was obviously an idiot if they didn't know how to use their own machine.

 

[JohnQ]

What do you mean by "the voltmeter began reading low"? That gauge has numbers. What exactly were you running at?

I'm with Darin, take your alternator to someone who knows how to test it. Whoever you talked to at the parts store was obviously an idiot if they didn't know how to use their own machine.

It was reading just above 8 with the needle pointing where the orange paint on the face begins.

 

[GLTHFJ60]

It was reading just above 8 with the needle pointing where the orange paint on the face begins.

Gotcha. That indicates that the alternator was not charging the battery and it was reading around 8 because it was under load.

Definitely take that alternator to get tested, or better yet, I have a factory 2F alternator I can ship you for not much. It worked great on my 2F before I ripped it out.

 

[GarnerFJ40]

Did you replace with a new belt when you replaced the alternator? Possible slipping? Sets in the pulley groove nicely?

 

[JohnQ]

Did you replace with a new belt when you replaced the alternator? Possible slipping? Sets in the pulley groove nicely?

All belts are new but there could have been some slipping I suppose since the pulley on the reman'd alternator was a little narrower than the stock alternator. Even so, it still tested bad on the bench.

I opened up the stock alternator tonight and the brushes are very worn. Voltage reg looks to me to be in bad shape also but I don't really have any past reference to go on with that.

Ultimately, I'll likely just rebuild the stock alternator and when the replacement for the faulty reman'd gets here I'll put it up as a spare.

 

[JohnQ]

Gotcha. That indicates that the alternator was not charging the battery and it was reading around 8 because it was under load.

Definitely take that alternator to get tested, or better yet, I have a factory 2F alternator I can ship you for not much. It worked great on my 2F before I ripped it out.

Thanks for the offer but I'm going to probably rebuild the stock one I have here.