I replaced the probe with one from antother year I now get voltage at low pressure switch but still not getting power to compressor unless I bypass the relay. Any other ideas?

 

Ok so thats a start. What is the ambient air temperature?

 

Around 70.

 

Best guess is its overcharged or has air contamination and the high side sensor is shutting it off.
Its nearly impossible to "guesstimate" the current refrigerant charge at 70F ambient air temperature. Most automotive a/c guys who charge by feel (i.e. guestimate) wont even attempt it til ambient air temp is over 80F because its just soooo easy to overcharge.

Correct procedure is really the only way at low ambient air temperature: remove the refrigerant with a recovery compressor & recovery cylinder, pull full vacuum and let it sit for 24 hours to check for leaks. Then look up the correct amount of refrigerant and using a scale, recharge with fresh refrigerant to exact factory spec.

 

The garage I took it too said they put a vac on it and filled it to factory spec. Today it's 80 I forced the clutch to engage and it's at 45 low and 100 high is that what I should see?

 

I know I'm gong to get pushback from this but unless its a dealership, most of the Brake/Muffler/A/C shops don't even bother to check if their a/c guy has a license. For the record I am an EPA licensed MVAC/HVAC technician with 37 years (god has it been that long?) automotive experience.

The exact psi reading will not tell you much except wether or not your compressor is working/failing or if you have an obstruction in the system. This is true of all chloroflurocarbon based refrigerant systems. Generally readings of 45/145 are typical at such low temperature but (assuming R134a) but I've seen high side readings as high as 350 on perfectly tuned systems at 97F ambient.

Check system pressure with vehicle OFF, A/C OFF for at least an hour. What are your high/low side pressure readings? They should be identical and 69psi at 70F ambient, 82-85psi at 80F ambient. Higher numbers than this are a sign of air contamination.

 

What finally happened with this? I need that very part, and it is not available anymore.

 

What part?

 

Thanks for a reply, the part number was mentioned above. 55036447. Blackvan responsed that it should actually be called Evap Core Sensor, his discription of what it does is what is in the Factory repair manual. I broke the aluminum probe at the plastic body, replacing the Evap core itself, Their are 2 white wires inside it which were not severed, I was just going to Glue the aluminum back together and hope for the Best, if I could not find a replacement for it. everything I find on it says it is a discontinued item. Amazing everything else for the AC system on my 2001 Ram van 3500 is available, but not this possible electronic nightmare part.

 

Yeah, I think that one is going to be fun to find..... Maybe on the used market?