Alternator belt squeal
 

Guys my 89 vert has a squeal from the alternator at high RPMs. Had alternator tested, it’s fine. Tried several types of belts . Cures it for a while, then comes back. I’m afraid I’m tightening the belt too much.
suggestions?

Maybe too loose. How much deflection in the belt?

Check the belt tension/deflection per the FSM procedure, belts that are too tight or too loose will squeal.

Another point is if you removed your air pump, and are only running a single belt on the alternator/water pump, you really need to get a dual belt alternator pulley. With the air pump removed, there's not enough belt contact on the WP to give enough traction to reliably run both loads with the FSM specified belt tension.

Thanks
 

I’ll check the FSM, air pump still on.

Check the fan clutch tension and the water pump weep hole for leaks.