grinding noise where is it from/not alt..

[rental blazer]

i took the altanotr off and had it tested its in perfict cond. so that leaves me with when i turn the a/c on i hear a sound like brushings going out in altnator sound however the alt. has NO PLAY NO WOBBLE AND PASSED THE TEST PERFITLY i i wonder is it the a/c compresser clucth or is it the belt tenster the belt is tigth so.. anyone have any idea's its only when the a/c is on when it makes a grind nosie and it blows cold

[OverBoardProject]

Is it not a single belt system?
If that's the case then it'll have to be in the compressor

[muddog321]

All they test is charging I believe. The front bearings can be getting worn if it grates or grinds when you rotate the pulley. Look at the fixed idler pulley next to it and the spring loaded tensioner also - they are cheap and are known failure items with age and heat - again with the belt off rotate them and listen and see if lots of play. When you turn the AC on a big load or drag is applied to the belt and all pulleys under it. The water pump can also grate so check the weep holes on it to see if any coolant starting to leak out.

[rental blazer]

Originally Posted by muddog321

All they test is charging I believe. The front bearings can be getting worn if it grates or grinds when you rotate the pulley. Look at the fixed idler pulley next to it and the spring loaded tensioner also - they are cheap and are known failure items with age and heat - again with the belt off rotate them and listen and see if lots of play. When you turn the AC on a big load or drag is applied to the belt and all pulleys under it. The water pump can also grate so check the weep holes on it to see if any coolant starting to leak out.

i have a new eng w/ 2 k miles so i know its not the waterpump as that was included with the new motor as its required to change cooling sts. such as rad. etc... to have warranty on motor so that leaves me with the pully or a/c due to the fact the alt did not have any play when i had it off..thanks gusy keep the ideas pouring in....

[BlazerLT]

Sounds like alternator bearings.

When under load from the belt and warmed up, you will hear the noise more pronounced.

[hunter01]

Sometimes you can use a big screwdriver or wooden dowel like a stethoscope by placing it to your ear and then touching the different accessories with the other end to hear which one is making thre loudest noise.