I just bought a 98 Dakota Sport 4x4 with 5.2 V8 and the AC would not work. Got it home and started checking it out and got it going but clutch cycling and not cooling, put on a cheap gauge I have and it shows Freon low, add 1 can and system is cooling good, shut it off to run down to parts store for a can with AC oil it. Then start truck to put the oil in the system but now the compressor clutch wont kick in. My guess is a bad switch somewhere but which one would it be? I changed the clutch relay and still wouldn't engage.

 

Will it start if you jump the low pressure switch on the accumulator (receiver dryer)?

What were the pressures high and low?

Don't be surprised to find you may have a leaking evaporator, in the dash. It's kind of common.

 

mornin all, i have similar prob. with my 2000 3.9-comp. wont run at all. iread somewhere to jump comp. from bat. but would like to hear it again, plus where is low press. accum. switch to jump also

 

Go buy a set of gauges from Harbor Freight, they are $45, don't mess around with adding more R-134a until you know for sure that is what you need. Same with the oil...

AC parts aren't cheap to replace and can easily be destroyed by overcharging the system. If your system is low on freon, it likely means you have other issues, check it out properly.

 

quick ?- after checking over my 2000 3.9 I found ac compressor does kick on but cycles off on off on. is that normal? still blows warm,

 

It's normal for it to cycle but at what rate? It depends upon temp, etc.

Throw on a set of gauges, real HVAC gauges, that can give us high and low pressure readings.

It is the ONLY way to diagnose an a/c system.

 

And don't trust the gauge that comes on a can of R-134. Those things have been known to be waaayy off.