I just got my first Volvo, a 1998 S70.

After driving my first 50 miles, I began to hear a horrible noise under the hood. My dad, the mechanic, determined it was the AC compressor running constantly whether the AC switch was on or off. We have disconnected it to make it quite.

Any ideas on what is going on here?

 

Did you have the defroster for the windshield on?

 

No the defroster is not on.

 

If it was stuck on then either the relay went bad or the clutch seized up and was staying on.

 

tech: thanks for the reply. its getting warm and im trying to figure this one out again.

my mechanic (my dad) noticed the compressor isnt kicking on immediately but a few seconds after engine startup. i also just removed the relay and the compressor did turn off. do you have a wiring diagram on that relay so i can check to see if its good.

ive been leaving the compressor unplugged to keep down on the noise and prevent lockup.
also, we arent seeing the fan turn on when the system is turned on from the cabin.

 

Open the relay and inspect it or swap it out with another one.
Also if the cooling fan is not coming on then the compressor should shut down once the high pressure gets to high.