Noisy alternator

Wooluf1952

Original poster
Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Looking for info on a noisy alt.

The alt on my 2003 Envoy is noisy, especially at start-up. I've confirmed it is the alt using a stethoscope. Also, the voltage is a bit low at idle (the gauge fluctuates around 11.5-12.5 volts), the t-body is clean, the RPM's are right at 600 and HVAC has no affect on it.

I know it needs to be replaced, but I want to change the t-stat, the temp sending unit and it's almost time for a coolant change. So I'd like to do it all at one time.

My question is to those that have replaced one:
Did you replace it because it failed?
Or did you replace it because the noise just got to irritating?

Thanks for any in-put.
 

CaptainXL

Member
Dec 4, 2011
2,445
Wooluf1952 said:
Looking for info on a noisy alt.

The alt on my 2003 Envoy is noisy, especially at start-up. I've confirmed it is the alt using a stethoscope. Also, the voltage is a bit low at idle (the gauge fluctuates around 11.5-12.5 volts), the t-body is clean, the RPM's are right at 600 and HVAC has no affect on it.

I know it needs to be replaced, but I want to change the t-stat, the temp sending unit and it's almost time for a coolant change. So I'd like to do it all at one time.

My question is to those that have replaced one:
Did you replace it because it failed?
Or did you replace it because the noise just got to irritating?

Thanks for any in-put.

Either or. A good alt shouldn't be making any noise. In fact it could be a sign of impending failure of the bearings. If you are only reading 11 volts then the alt has failed. It should be charging at a minimum of 13 volts. Remember the alternator doesn't charge the system, it charges the battery. And the battery is 12 volts. So the alt need to constantly charge higher than that to replace the draw on the battery.

In my case. I replace them when they are getting too noisy taking into consideration mileage. But I have had alternators go out before they were noisy. If you get a carbon pile or any other load placed on the battery the voltage output on the alternator should increase.
 

Sparky

Member
Dec 4, 2011
12,927
I replaced mine because the bearing was making a racket.
 

Wooluf1952

Original poster
Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Thanks guys.

As stated, I know it's going. The gauge reads 14 volts while driving. Then drops down at idle.

In days of old, when knights were bold. OOPS, wrong forum. :biggrin:

Anyway, time was I would just rebuild the old one. I'm not sure if rebuilding parts are even available any more.

I've got a trip tomorrow, about 250 miles round trip. So I bought a new alt and will take it with me just in case.

The alt has been making noise for quite a few month, so I should be OK.

I know what I'll be doing this weekend. :yes:
 

Decembersend

Member
Dec 3, 2011
316
I replaced mine a couple of years ago do to a burning smell turned out to be an open diode that Midas almost missed. They claimed they didn't smell anything and that I must have accidentally turned on the heat in the middle of Oct. here in Fl. :no::crazy:.

In the end I replaced the new aftermarket for a HO Alt for my stereo.
 

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