97 Dodge Ram that has had awesome cold air for years. then, started to blow warm air. A/C clutch cycles on for 2-3 seconds and off for 8-12 secs.

I checked the pressure with an AutoZone single gauge set up (yes I've read the posts on these killer items) and it reads 45 when off. When I turn the ac on the the clutch engages and the gauge drops to 25 and then shuts off (takes about 3 seconds). Then continues to cycle, 8-12 secs off, 2-3 seconds on.

I jumped the switch next to the compressor with no change in cycling.

Jumped the switch on the evaporater cannister and the clutch stays engaged and blows cold air.

I'm thinking its the switch on the cannister.

Any thoughts?

possible switch, possible leak also the pressures sound pretty low

It's low on 134A, nothing wrong with switch. It's a 97, so it's almost guaranteed the evap core is shot. You can get some 134a with die in it and use a black lite to look for leaks, if you don't find any under the hood, then it's the core. It's the only place you can't see.

thanks folks, I added a can of R134 and blows cold again. I'll wait and see how long it takes before it's low again to determine whether or not it's worth it to replace the core.

Definitely an evaporator leak.