Archived Dead AC

[WAM]

On a 2006 Ram 3500 CTD, I suddenly started overheating towing uphill. Turned around and was limping home when I got caught up in an Ag inspection station and suddenly the AC quit working. I had been running the AC because there was no overheating when not hill climbing. Outside temp 109 F.



Took it to a shop who replaced the fan drive. It's ready to pick up, but they were unable to diagnose the AC trouble. They verified no voltage at the compressor clutch, also no voltage at the high-pressure cut-off switch. They looked for but were unable to locate a low pressure switch. They really don't know what to do next.



Am in a small town out in the desert and our only Dodge dealer fell victim to the recession. Would sure appreciate some input from someone who knows these systems. I don't, and neither does the local "talent".

 

[RAB]

I do not recall seeing a low pressure switch on 1 in the shop earlier (mass contamination)First thing i would do is verify the pressure on the system. verify that i had a ground at the comp plug (unplugged), verify clutch activated with 12v (unplugged). Each on will lead you down a different path to solving the problem.

 

[WAM]

Just so I understand your thinking. Given that there's no voltage at the high pressure cut-off switch, why would we suspect/check the pressure? A dead switch shouldn't know or care about pressure. I only balk at this suggestion because I don't have any manifold gauges.



It would really help if I understood the system better. The compressor clutch is run by +12V. Does that current come directly from a relay maybe? Or is it routed via the high-pressure cutoff switch. I ask because I'm thinking of "hot wiring" the system to get through the coming weekend. And I'm wondering if I supplied a hot wire to the high pressure switch would the current pass through and on to the compressor? Or is the high pressure switch not "in-line" with the compressor but rather an input to a computer or relay or something.



I can't see spending nearly $500 for a shop manual. Any way someone can post the applicable AC wiring diagrams? I can probably figure this out eventually, but it would sure help to know what I'm dealing with.



Maybe there are even wiring diagrams here on TDR? I'm new here, so dunno.

 

[chipster]

I`ve got the same problem on my `06 dodge. I`ve checked the pressure in the system, it has 115 psi on both sides at about 110 degrees outside. the system has no low pressure switch that I can find. but the system has more than enough pressure to function a low pressure switch. I don`t know if the ecm or a body control computer runs the A/C system. If anybody knows how to diagnose this system, please chime IN !!!

 

[WAM]

Moving along -- I couldn't find a 2006 Ram wiring diagram, but I did borrow a shop manual for a 2000 Ram. It appears the compressor is directly controlled by the AC relay. The relay is activated by being grounded in the PCM. None of the pressure switches are in this circuit. Instead, they supply information to the PCM. That's going to make hot-wiring harder. I can jury-rig the relay to provide power to the compressor, but I won't have high or low pressure protection.



I can still do it, if I rewire the high pressure switch to control a new 12v relay I place in the compressor power line.



But before I hack anything up, I can now troubleshoot the AC relay if the 2000 wiring diagram is close enough to my 2006 truck.

 

[Simplysmn]

It also could be a TIPM Problem I am chaseing the same problem with my 08 n dealer changed the pcm and then the tipm then called and said clutch on A/C compressor was bad but the wanted 800 to change it I got a complete kit for 415. 00 free shipping

 

[Missouri Mule]

On 96 trucks there is a low presure switch located on the accumulator it sends a signal to the PCM and the PCM turned on the AC clutch.



Apparently they did away with the low pressure switch.



If there is to much pressure in the system the high pressure switch will turn it off.

I had my high pressure switch die and it killed the AC.

 

[mweiman]

I am not sure about the ac controls on our trucks, but have you checked for fault codes? On some trucks(International) if you set a fault code for the a/c it will turn off the a/c until the code is cleared. I just wonder if you got a high pressure fault of some kind when your fan quit. Maybe try clearing fault codes or unhooking the batteries for a minute and see what happens. Not sure about this just throwing ideas out.