I have a 2001 4x4 Ram 1500 5.9 automatic.

Tried to charge the a/c and could not get the compressor to turn on.

A/c switch in dash set to on, fan set to high, fuses are good, traded the compressor clutch relay for the wiper relay (wipers worked), jumped the low side pressure switch, then jumped the high side switch as well when there was no change.

With both, the high side and low side jumped I unplugged the compressor clutch and checked for 12v coming in … none.

What am I missing?

Thanks for looking.

 

Try putting a jumper across the relay terminals for the compressor. The pressure switches are on the control side of the relay circuit.

 

Thanks.. Went back to it today and tested the connector, I get a perfect OHM across the terminals leading to the clutch. while i could be wrong, I would think they would be pos and neg terminals. I fear it is burnt out but will look into jumping the relay next time.

 

Define "Tried to charge the a/c" . What exactly did you do ?

I just charged mine so I will share since it sounds the same right now .

Turn on AC , nothing . So , shut off vehicle , connect your recharge kit and open the can to allow pressure into the system . After a minute or so , start truck , AC on blast and alow it to circulate . This should start the compressor as it did with mine . First an on - off then a steady on . I only used 1 can to get it running , and maxed out in the safe area of the gauge . AC is now ice cold . When I first hooked up the gauge , it read high until started . Once the compressor kicked in and started to cycle on and off , it would drop . Once a decent pressure is reached , it will stay in cycle , and the pressure reading steady in the safe/green area .

 

Thanks. Think I will include the long version this time. Truck belongs to my uncle. He calls telling me that he needs me to add a can of freon to his a/c (I recently moved back to the area). I asked how long this has been going on and he said it started last year every and few months he needed to add a little freon. I told he we would take care of that. He indicated that the compressor would cycle so I did not check it.


The freon he had been adding was that walmart stuff with leak die in it so I got lucky there. I grabbed my light and glasses and found the inlet connection to the accumulator /drier as well as the inlet to the evaporator showed leaks. Ran up to my local O'Reilly and got an O-Ring kit for the truck and installed all new O-Rings throughout. Note: there was NO freon in the system.


Hooked my gauges, vacuum pump, and compressor up and vacuumed the system down for about 20 minutes and -18 inHg. Let stand for 30 minutes and held, I was fine with that, wasn't expecting perfection anyway. As is norm, first can sucked right in and, baring any problems, this is where I would expect the compressor to kick on. It didn't so the diagnostic process begins.


First thing was the jump the low side pressure switch, normally that will do the trick, but not in this case. Next was to jump the high side pressure switch (low side still jumped) and again, no joy. Checked the fuse and swapped the relay with a known working one. Still nothing, having all ths done I unplugged the compressor clutch and checked the incoming connection for a signal and got nothing.


That is when I came here. Stumped. But knowing most responses happen to shorter forum postings I gave the short version indicating all the important key points.


Yesterday I want back to truck and checked the OHM of the compressor clutch. It was 0.0ohm indicating to me that there is a short and the clutch needs replacing, but that still does not tell me why there was no signal going to the compressor with the switches jumped.

 

You don't need to jump the high side, it is a high pressure cut out so it already has continuity across it. You need to check if the relay is triggering and getting power out first. Then work you way through the pressure switches to the compressor coil.

 

Thanks... I took a known working relay (wiper) and swapped it with the compressor relay, no change. Wipers work as well.

 

So the relay is fine, it's the control circuit that is the issue.

What year is your truck? Are you testing with the engine running? Wonder if the PCM won't trigger the circuit if it isn't...... Are you getting any voltage indication on either of the pins on the low pressure switch?

 

year is 2001
yes, checking with engine running, haven't checked for voltage to the pressure switches, did not think of it to be honest. no longer having access to alldata keeps me from checking pins coming out of the pcm.

 

Grab the 01 service manual from this thread. Wiring diagrams, connector pinouts/locations, and all sorts of cool stuff in there.

Yeah, check and see if you are getting power the brown wire. On your truck, voltage is supplied by the PCM, so, not sure if it will be 5, 8, or 12 volts...... the circuit runs to the HVAC control head, and just grounds out if a/c is requested. (dial set in the right spot.) PCM senses the closed circuit, and then triggers the compressor relay.

Damn that is convoluted....... wonder why dodge decided to make things so complicated.