Symptoms


Summer


Turn on AC. Works fine but screeching noise and stops once at >20 mph.


Winter


Turn on defrost. Works fine until rear defroster electric goes on. Then at >20 mph is fine.




I think fan clutch since AC and defroster use it and additional power puts stress on defroster.

 

It could be the belt is loose or glazed. A belt subjected to slipping tends to glaze over and slip even more. The only real solution is to replace it.

Can remove the belt from compressor. Then power the magnetic clutch to check for binding of compressor when rotating pulley.

Are you using A/C to help with car defrosting? If so the combination of A/C compressor, defrost electric fan and rear electric defrost load on the alt could be causing the belt to slip.

 

I only depress the defrost button for rear window and turn on defroster dash button front. The ac dash button is not pressed.

Your suggestion. Just want to make sure.

1, Check if belt is loose.
2.Remove pulley and check for glazing.
3. Power the magnetic clutch. Car is not on just key turned to power it, press ac button.
4. Rotate and feel for binding.

 

Is it winter or summer at your location? What is the outside air temp when starting engine?

With engine running. Have someone turn on front defroster while you watch the A/C compressor. Determine if the compressor is engaging. This being the magnetic clutch is locking up to rotate the compressor shaft.

While watching. Listen to the accessory drive belts to determine where the noise is screeching noise is coming from. A section of hose can be used as a stethoscope to help narrow down the area.

Check the A/C clutch pulley and alternator. The other drive belt is for the power steering.

 

Makes sense. Got it. Thanks.

Winter now but warming up to 40s. Chicagoland area.

 

Sorry Toyomoho I should of checked belt first.

Belt was loose. Loosened main bolt on alternator, then adjuster lock bolt or whatever you call it. then screwed adjuster bolt to tighten belt. Retightened.

AC on and no screeching. Thanks.

 

Great job. Thanks for posting back with the fix.