Hi - have an AC problem that in the words of my normal mechanic: "defies all logic"

basically - the AC clutch refuses to engage. We can force it to engage by jumpering around different pins on the relay. If I leave the relay in place and slightly pull it out to access the pins - if I run a wire from pin 85 to the negative battery terminal the clutch engages. I am currently using this as a "jury-rig" so I can have AC to drive my truck. Afternoon temps around Houston are 100º+ everyday and driving around without AC is HOT HOT HOT.

If I remove the the relay completely and apply +12V to the socket (in the fuse box) for pin 87 - the clutch engages.

We have tried swapping relays and that did not fix the problem.

His Snap-on code reader can do a functional test and the clutch engages. All other read-outs from the reader indicate no problems.

It has a full charge of refrigerant, and the condenser fan seems to be working properly.

I should ad that my AC was having an issue prior to this. It would randomly stop working (turn off). To get it to come back on I had to either bang on the steering wheel or operate the tilt mechanism and the AC would come back on immediately. I told the mechanic this and we did disassemble the steering column and found that some wires had overheated, so we replaced the electrical portion of the switch. I've seen pictures of other Dodge trucks with the same overheating condition at the switch connector.

Any help is appreciated!

 

I personally would check the fuse box. I think Dodge call it the Power Distribution Center.
I and many Rams have had issues with the underside of the fuse box getting wet and the corresponding printed circuit board within it, corroding.
This leads to either intermittent and open circuits and also high resistance circuits, which cause in my case the front control module not to switch my park lights on. A very common issue with Dodge Rams.
I myself jumpered the park lamp relay exactly the same as you did for your AC to work, to get my lights to come on.
I eventually repaced this fuse box and I and many on this forum, have found that it cures 100% of these problems.
I have read of many issues revolving around main headlights not coming on and of course the park lights issue.
Hope this helps?
Al.

 

turns out it was the Evaporator Temperature Sensor.

replaced it last night and it works like a charm.

 

Hate it when that happens ...

 

Damn, that was my thought too---evap temp sensor, its there to prevent the evap from forming ice, which once it starts, blocks air flow, and causes more ice

 

it would be nice if I could have bought just the sensor...but NOOOOOOOOOOOOOO, Dodge makes you buy the whole evaporator.