I have a 95 Tahoe with the an R4 compressor. After the AC has been running a few minutes I get a growling rattle sound. I turn the AC off and it's gone. It is most noticeable coming from the alternator. Even using a stethescope it is loudest at the alternator. Pressures appear normal. I suspect it's my aging compressor going out making the noise. I thought it was being caused by an old tensioner so I changed that without making any difference. The alternator and AC both spin freely by hand with the belt removed.
Alternator rattle with AC on
- Thread starter 95 Tahoe
- Start date
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someotherguy
Even more awesome in person
I've seen a practically new (cheap) tensioner be the source of excess noise when the compressor engages, so don't write off the tensioner as the cause just yet. *Very* carefully use a pry bar, broom handle, etc. to hold the tensioner still so that when the compressor engages, you can see if it's still making the noise or not. Really, be careful that you don't get yourself caught up in the moving belt, fan blades, etc.
If it's not the tensioner, my -guess- would be the bearings in the alternator are going bad but just not bad enough to make noticeable noise when free spinning; it takes the extra load on the belt drive of turning the A/C compressor to make it speak up. Don't think I've seen that particular failure though.
Richard
If it's not the tensioner, my -guess- would be the bearings in the alternator are going bad but just not bad enough to make noticeable noise when free spinning; it takes the extra load on the belt drive of turning the A/C compressor to make it speak up. Don't think I've seen that particular failure though.
Richard
I went and checked it again after driving. I definitely feel a metallic drag in the compressor now. It is on its way out. I have no idea how old it is. I resealed it 2 or 3 years ago. I"ll run it until it stops cooling then replace everything.
Chevyman1969
Newbie
Good job, hope this helps other out aswell
someotherguy
Even more awesome in person
There's definitely drag on the belt drive system when the compressor engages, and can make marginal items in the assembly talk to you. You looked closer and found what it was. Good job!
Richard
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