Alternator went out now new one gets hot when A/C is on

TANNER112

MEMBER
1995 FORD EXPLORER
4 CYL
2WD
AUTOMATIC
12,000 MILES

My alternator went out and I had a new put in. At first it was running good but then I noticed it was making a loud noise and got extremely hot anytime the A/C was on. I took that one back and had it swapped out for another one. But it is still doing the same thing. Any ideas?

3 Replies

HARRY P

MECHANIC
2,293 POSTS

It sounds like there is a bad bearing in one of the pulleys. Are these alternators brand new? Are you 100% sure that it is coming from the alternator, and not some other pulley right next to it? Often times it is a guide or tension-er pulley that is making all the noise.

You can hand check all of the pulleys when the engine is cold. Just take the belt off and start turning them by hand. The crankshaft pulley will not turn though. The others should all turn smoothly and freely. If you find one that does not, that is your issue.

Guide on taking the belt off and putting it back on: https://www.2carpros.com/articles/replace-serpentine-belt

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Monday, September 4th, 2017 AT 7:58 PM

TANNER112

MEMBER
2 POSTS

Thank you, yes I am 100% sure it is the alternator making the noise. The first one was a brand new one, and then the second one we got a rebuilt one. Both have been checked from the auto parts store and they say they are both good. As soon as you unplug the alternator or turn the A/C off the sound goes away.

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Tuesday, September 5th, 2017 AT 5:08 AM

HARRY P

MECHANIC
2,293 POSTS

To me that sounds more like a bad A/C compressor. Take the belt off and check the pulleys as I described earlier. I bet that compressor does not turn smoothly when you turn it.

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Tuesday, September 5th, 2017 AT 8:14 AM