Ac compressor problem

Put freon in it and see what it does, a/c clutch engaged, engine on.

High side should rise, low side should lower

 

When the clutch comes on for 10 seconds do the pressures on the gauges change at all?

 

Yeah, but it appears it's not working cause it ain't got enough freon.

Put more in, see what happens. Or pay someone that knows what they're doing

 

If the system is full and the compressor only runs for 10 seconds before cutting out, you have a severe restriction causing the low side to pull a vacumn (plugged orifice tube or bad TXV. Or... a bad low pressure cutout switch.

 

The pressures will tell you if they are not correct and you have the truck running and the proper amount of freon in it.

 

And/or possibly a high pressure situation causing it to cut out (plugged condenser, low air flow, etc) Guages will tell the story.

 

20 psi shouldn't be low enough to open the low pressure cut out switch so its possibly bad.Bypass it with a jumper wire and see if it works