hi guys.

i tested something with the car to rule out a non fuel system related problem, the car makes a weird "knocking" sound when you turn on the AC, so i decided to test the car in a road trip "60 miles" at 60 mph to see if turning off the AC or not using it at all would make any difference.

to my surprise the car ran fine all the way, all the 60 miles "twice" at a constant high speed, so i checked the AC compressor, and it looks like its not working well "it does give cool air" but it looks like at some times the belt just spin and the compressor makes a grinding sound and it has a constant knocking sound when turn on like if it had a loose screw or bolt.

so since i know nothing about AC car systems, can the source of the problem be a faulty AC compressor?.

It'* possible for an A/C compressor to stall an engine, unless a belt snaps first.

Grinding noise usually indicates excessive play in the clutch. But, if the A/C is turned on and the engine idle goes down to a stalling point, turn the A/C back off. I suggest disconnecting the electrical connector from the A/C clutch until you get a new compressor.

knocking sound means it is overcharged. the grinding is a bad clutch.

Not necessarily, bad. It could be out of adjustment which can be fixed with the clutch plate adjustment tool.


https://www.gmforum.com/mechanical-1...-plate-278951/

what does it means that its overcharged?.

also the knocking sound goes away when driving "with the ac turn on", it only appears if you park and keep the ac on, also both sounds "grinding and knocking" do not appear if you dont turn on the ac.

Then the noises are attributed to your A/C compressor. Which like said early, is probably on its way out or needs the clutch readjusted.

the compressor could be overcharged with freon ( more likely you got refrigerant recharge recently?)

or undercharged , low supply of refrigerant, could be system leak causing freon leak and allowing air to get into your system making the compressor work harder (noise/hesitation) and blowing cool air, but not freezing cold air