Alternator or Battery?

[GMCGoat]

I took the alternator and battery out of my truck. Need to get them tested first but from what I know, when a vehicle is running and the alternator is working correctly, the battery should read between 13-14 volts.

In my case, when vehicle was running (after boosting it), the alternator was only reading 11, then 10, then 9. then I shut vehicle off and of course it didn't start.

Thoughts?

I'll get some free tests at Napa or something tomorrow.

I'll clean all connections, check negative to frame connection before re-installing.

PS. Do I need anti-seize on my pivot bolt and/or adjusting bolt?

[Wrenchbender Ret]

You are right. It should go up to about 14 volts when it is running. It's obvious your charging system is not working.

[mr48chev]

Originally Posted by Wrenchbender Ret

You are right. It should go up to about 14 volts when it is running. It's obvious your charging system is not working.

Yep, somewhere between 14 and 14.5 is good with 14.2 being ideal by what I learned years ago.

You are still going to need a full charge on the battery before they can test it unless they have some real sophisticated equipment.

If the alternator is putting out what it should and has no blown diodes and the battery checks out it's time to check out your wiring and see where the break or restriction is.

The last time I was at Bonneville with my 48 I spent a few hours getting my battery charged and troubleshooting the electrical system only to find that I had a broken wire right at the alternator. Got it fixed and made a banzi run across Nevada until I started hallucinating on the paint stripes and pulled off at the Valmy rest area for a nap. I stretched out on the lawn in my sleeping bag and bailed out a few hours later when I heard the distinctive pop of a sprinkler getting pressure to it. I moved fast enough not to get wet and gave a couple of truckers a great laugh in the process. But the gist of the story is along with checking out your battery and alternator take a bit of time to check out the wiring to make sure it is good.

[GMCGoat]

Thanks guys.

[Zach B]

Sounds like the altornator needs replaced.
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[parkwood]

If your alternator is working like it should hold a piece of metal to the back of it and if it sticks it's charging, if not it needs to be replaced.

[mr48chev]

Originally Posted by parkwood

If your alternator is working like it should hold a piece of metal to the back of it and if it sticks it's charging, if not it needs to be replaced.

I haven't heard that one for 30 years, you must have been spending a bunch of time with the good ol boys down at the spit and whittle club.

Actually in the hands of someone who doesn't know much about what he is doing with an alternator that is probably a great way to short it out and blow all of the diodes out. You can buy a multimeter for chump change why risk shorting something out using a method that may or may not have worked when old Fred thought it up 50 years ago.

Maybe it's the old shop teacher coming out in me but I would much rather see guys give solid advice and instructions to someone who is struggling with something a bit and help them learn rather than come up with something that may or may not work that they heard about somewhere.

[GMCGoat]

Guy at parts store said it was the battery. weird.

I think I'll pick up my stuff and go to another parts shop to double check.

The reason this is so importnat is that the truck is supposed to be in a Canada Day Parade this weekend.

I asked the guy to test it a 2nd time to be sure (and mentionned parade) and he was reluctant....hate that atitude.

I might pickup the alternator just in case...return it if it isn't needed.

[mr48chev]

It could be that the battery would take enough of a charge to start the truck when it was cold but couldn't keep up with the demand when the engine was hot.

I'd put it back together with the new battery and old alternator, fire it up and check the output of the alternator. Worse case of buying one just in case is having that money tied up for a few days if you don't need it but that may trump not being able to get the truck squared away for the parade. It wouldn't be the first time one of us bought something just in case and then took it back later because we didn't need it and won't be the last.

[GMCGoat]

Took it to cruise night tonight with no problems.

[parkwood]

Originally Posted by mr48chev

I haven't heard that one for 30 years, you must have been spending a bunch of time with the good ol boys down at the spit and whittle club.

Actually in the hands of someone who doesn't know much about what he is doing with an alternator that is probably a great way to short it out and blow all of the diodes out. You can buy a multimeter for chump change why risk shorting something out using a method that may or may not have worked when old Fred thought it up 50 years ago.

Maybe it's the old shop teacher coming out in me but I would much rather see guys give solid advice and instructions to someone who is struggling with something a bit and help them learn rather than come up with something that may or may not work that they heard about somewhere.

Yes it's the shop teacher coming out.... if a guy can't touch the back of an alternator in the center where there are no wires to touch and without blowing the thing up then he shouldn't be playing with cars...about the best solid advice I can give.... I've done it hundreds of times and never blow anything up..

[mr48chev]

Originally Posted by parkwood

Yes it's the shop teacher coming out.... if a guy can't touch the back of an alternator in the center where there are no wires to touch and without blowing the thing up then he shouldn't be playing with cars...about the best solid advice I can give.... I've done it hundreds of times and never blow anything up..

There is really no politically correct way to say what I am thinking so I will not say it.
I will go back to what I stated before. When someone doesn't seem to have a lot of skills I think it's prudent to give proper testing info rather than a shade tree test method. The man already stated that he had a test meter along with taking the alternator to Napa to have it tested.

[OrrieG]

I still use that shade tree method as a "go-no go", then move on to the meter. And Mr48 you are right alot of the time it is a bad battery terminal, failing crimp, short starting etc. but it seems it really should be something more complex. One of my main diagonostic tools is a 6 foot piece of wire with alligator chips on each end to jump around suspect wiring.

[tttuba]

One way I have tested the alternator on old cars....NOT new computer cars is once started take the battery out of the equation by disconnecting the NEGATVE battery cable. If it continues to run, turn everything on inside and if it didn't die, it has enough to keep up with the load. If it dies, the alternator is bad.

[lazypineapple]

And this is a good way to ruin an alternator.

Originally Posted by tttuba

One way I have tested the alternator on old cars....NOT new computer cars is once started take the battery out of the equation by disconnecting the NEGATVE battery cable. If it continues to run, turn everything on inside and if it didn't die, it has enough to keep up with the load. If it dies, the alternator is bad.

Posted via Mobile Device

[mr48chev]

Originally Posted by tttuba

One way I have tested the alternator on old cars....NOT new computer cars is once started take the battery out of the equation by disconnecting the NEGATVE battery cable. If it continues to run, turn everything on inside and if it didn't die, it has enough to keep up with the load. If it dies, the alternator is bad.

That works but again is in the Duck Dynasty methods of doing automotive testing. And as lazypineapple said is a good way to blow the diodes in an alternator or even worse blow expensive electronic pieces in the rigs.

Chrysler perpetuated that one when they first came out with alternators in the late 50's early 60's when they took the batteries out of two cars and drove them several hundred miles cross country. Since the early 60's I've probably had 300 guys tell me that I can check an alternator that way while I am hooking up the test meter on their car.

There are a lot of shade tree methods of testing and doing things on cars and Jim Willy over at the wrecking yard that was within walking distance of my house when I was a kid showed me most all of them but that doesn't make them the proper way to do things. You can imagine what the results will be if you short a pair of pliers across the top of a battery to see if it gives a nice spark to show that it is charged up will be most of the time but Jim showed me that one when I was 16 and needing a battery for my 51 Merc.