Alternator dead?

BlackVert

BlackVert

15 Year Member
Oct 3, 2003
5,589
9
98
Bethesda, MD
#1
I think my alternator must be dead. Symptoms:

After I charge my battery and start the car, there is a terrible squealing noise after a few minutes. Also, the voltage gauge reads around 12 (usually it is closer to 14).

I just charged it a couple days ago and now it is dead again.

What can I do to either verify that is it the alternator or rule it out? Is an alternator the kind of thing that you can return?

Lastly, I think I must have my belt tensioned incorrectly. This is the 2nd alternator that has gone bad on me. How tight is it supposed to be?

I have March brackets and no tensioner.

Thanks,
 
#2
Is the battery light illuminated? If not, does the light prove-out when you turn the key on?

Put a DMM on your battery with the car off. Note the reading (12.6V is nominally charged 100% - your charger might have put it up around 13.X volts). Start the car and see if the reading drops. Turn on the headlights, fogs, HVAC fan and see if the reading drops more. It probably will based upon what you said. It should never go below 12.6V no matter how much crap you turn on, unless your idle is set at like 500 RPM or you have a huge underdrive.

If you want you can just have the alternator bench tested (take it out and to a parts store). You can also have a dymanic test done (the system is tested with the alt in the car - you can basically handle that with your meter if you choose. Testing yourself with a meter yields more precise results IMHO).

If you pass a bench test or want to test the wiring first:

Ensure the alt fuse (underhood fusebox) is not blown. Check that the fusible links in the charge cable are not blown. The reg is labeled A, S, I. Ensure A shows battery voltage, I shows 2-6V while the car is idling, and S floats ~1/2 battery voltage with the car running.

If your results vary, post up for a diagnostic pathway.

If you got your alt at a parts store, it might have a lifetime warranty. Otherwise, it will depend upon the vendor/supplier.
 
#3
Oh, tension. Too much or little does cause issues. I don't know a spec since the tension is supposed to be handled with the auto tensioner. Does the bracket supplier list a spec?

If you have doubts, I'd probably tension it on the loose side. If you're too loose (which can cause issues), you should be able to note slippage. We'd almost need deflection gauges to offer an objective comparison for you however.
 
#5
i took the alternator off tonight. it spins freely, but there is a slight, well, roughness (for lack of a better word) to the way it spins, almost like it would be if a little sand got in the bearings.

i know there isn't sand in there, but that is the best way i can think of to right now to describe it.

i'm taking it to autozone and my mechanic tomorrow for evaluation.

the AC compressor spins freely and smooth

the water pump has some resistance ... not a lot, but definately some

the power steering pump also has some resistance
 
#12
A loose belt can cook the alt bearings as well.

When you take it for the load test, you can hear bearing squeal (if an issue) when they put a big load on it.
 
#14
BlackVert said:
is this something i can do myself? how?
Click to expand...

I definitely agree with all of the responses, this can be caused by one of two things the serpentine belt or the alternator. Both fairly easy to install but one more expensive than the other. I would suggest to take the alt out yourself (very easy procedure) it basically just sits there in your car with one bolt locking it in and there is a plug in the back of it. Take the bolt out, unplug it, and if your standing on the passenger side pull the alternator towards you. Take the alternator in by its self and test it, if it is working properly and your still having car troubles there may actually be some fluid in your alternator, maybe from coolant or whatever, that doesnt show up as easily when you test the alternator you would have to take the alternator apart to see that. If there is fluid you need a new alternator that should fix the problem, if not check the serpentine belt.
 
#15
i took the alternator out tuesday night. i am going to take it to autozone to be checked over lunch.

getting it out was ... fun. i have march brackets and the top bolt was easy enough to get apart, but the bottom one was a pain because it is a huge allen headed thing and there is very little space, so i had to back it out one sixth of a turn at a time while fighting with the big coolant hose that runs above the alternator.

how would i get the shaft out of the alternator to check/replace the bearings inside?
 
#16
BlackVert said:
i took the alternator out tuesday night. i am going to take it to autozone to be checked over lunch.

getting it out was ... fun. i have march brackets and the top bolt was easy enough to get apart, but the bottom one was a pain because it is a huge allen headed thing and there is very little space, so i had to back it out one sixth of a turn at a time while fighting with the big coolant hose that runs above the alternator.

how would i get the shaft out of the alternator to check/replace the bearings inside?
Click to expand...

Well if your going to replace the bearings in the alt it probably wont be long before the regulator assembly to go bad a well. And if you have a bearing going out most likely it will have other issues like rectifiers or pulley wear. So if it were me I would go and check some prices on a new or rebuilt alternator.
 
#17
got one at advance for $155 with the core. it has a lifetime limited replacement warranty that replaces it twice if it goes bad. hopefully i'll be able to get the tension right before burning up 3 more alternators.
 
#19
You never told us if the old one turned out to be bad. And let me tell you from personal experience, Autozone and Advance have told me in the past that my alts were bad when in fact there were good. I still catch them hooking them up wrong and have to show them the proper way.

As for Autozone, their machine is a piece of crap! It's a stupid computer that just tells you if it's bad or good, nothing else.

I've been rebuilding these alternators for 6 years now so I know them pretty well. Bearings are super easy to swap and I've never once heard of "fluid" causing any issues if it did get in there. It's just a HUGE electromagnet so a little fluid wouldn't have the slightest affect unless it got into the regulator/plug.

Also, the regulator in these alternators RARELY EVER goes bad. It is usually the brushes that get fubard up. Either they get worn down to the nub or they break off completely.

I wish I would have saw this sooner Chris, I could have done a lifetime warranty POLISHED unit for 100 bucks! Oh well..I'm glad you got it fixed.
 
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