Hello, I have an ‘01 with the 4.0 and had recently charged my A/C for the season earlier this spring. It worked at first, but my compressor started acting up and would only kick on when I messed with the relay. Now it doesn’t work at all, I replaced the relay but nothing changed. I believe the switch is fine as it cycles through the different vent modes without issue. Any ideas of what it could be?

 

Welcome to the forum

The AC system/hoses, have 2 pressure switches, high pressure and low pressure

High pressure switch prevents hoses or parts from exploding if the system gets blocked

Low pressure switch prevents compressor(expensive part) from getting burned up when fluid/oil in the system is running low

The AC relay is grounded by these switches, so if either switch "opens" AC Relay cuts power to the compressor's clutch, turns compressor off, to prevent explosion or burn out, either would be a BAD THING, lol

You need to find the two switches in the engine bay
Each will be on an AC hose and each will have 2 wires

You need to use an OHM meter
Unplug the switch connector and test the 2 contacts on the switch for 0 ohms, that means switch is closed and pressure inside is OK, not 0 ohms means switch is open, so no AC

Either switch can be changed without draining the system, if you think its a switch problem.
Usually its NOT a switch problem, its a system problem, a leak or a blockage


If you jumped the AC relay then you may have burned out the compressor, so expensive fix