Hey guys, I would like to hear from some of the A/C gurus out there. My problem is that my A/C has become intermitten. Sometimes it works and sometimes it don't. The problem is almost certainly an electrical problem. I have checked the pressure switches by using an ohm meter on the high pressure switch and I have used a jumper wire on the low pressure switch and it does nothing. I have also replaced the compressor, liquid line, and receive drier and still nothing. When it works the pressures are right according to the Chrysler FSM. I have tested the relay in the power distribution center and everything tests out there. I have also pulled the switch in the dash and cleaned it and it appears to test out according to the pinouts in the Chrysler manual. I have also recently put a new PCM in the truck. I know that the PCM cycles the clutch by removing the ground. So, should one of the wires always have a positive 12-volts when the A/C is selected if the PCM cycles through grounding? Any suggestions?

 

have you checked the power side of the relay? sounds like you have tested the coil side. the 1 wire going to the clutch shud get power to activate clutch. also if you can get a hold of a scan tool when it does and see if the pcm has requested ac on

 

I have checked the power side. In the power distribution center relay I can take a jumper wire and place it between terminals 30 & 87 and manually cycle the a/c clutch. Or, I can also go to the PCM and manually place a ground to the C-3 terminal #1 designated for the a/c relay and manually cycle the clutch that way. But, it will not do it on its own. I have also checked the grounds associated with the a/c clutch. Also, my ambient air sensor and engine coolant sensor both read normal. What do you all think? Maybe a bad PCM? I just put the new PCM on the truck 1/17/2011. It was a unit that I had O'reilly's to order from A-1 Cardone. Do you all think that could be the culprit?

 

i wud call a dealer and get with them on PCM numbers it may be you have a wrong but runnable unit for your truck

 

When I did put the "new" PCM on my truck I had to take my old one to O'reilly's. After I talked to them they said that A-1 Cardone simply took my old PCM and refurbished it.

 

i've had problems out of IDM's for 7.3s from a1cardone befrore. do you have a buddy with the same truck you cud swap pcms with?

 

My uncle has a 1998 12-valve 5-speed. Mine is an auto. Would the two interchange?

 

for ac testing purposes i wud think so. you wont have any tc lock up or overdrive tho if you drive it. do you have access to a scan tool that you can monitor ac request with?

 

When I turn the A/C on, the terminal at the PCM that is designated "AC Switch Sense" should be grounded, right? I can use my multimeter tester with the negative to that terminal and the positive to the positive battery post and it shows the exact same voltage as the battery. Now, when I ohm it out (stick my negative to the PCM terminal and the positive to a battery or chasis ground) it reads something like 48-52 ohms. Should it not show continuity? Does that mean anything? I have already checked the ground under the dash that grounds the HVAC control. Thanks!

 

i have a schematic in my console ill check it out tomorrow and get back w you. ive not had these ac issues. where are you located btw if your close we can check it out

 

I am in Livingston, TN (about two hours east of Knoxville). I have the wiring schematics that are in the Chrysler FSM but I am not real sure exactly how to read them. Thanks!

 

you mean west of knoxville. i take trips to crossville periodically. ill pm you my phone number and you can do the same. we can meet up when im out that direction next time. unless you are in knoxville from time to time.

 

Yes, I mean west of Knoxville. You are two hours east of me. That sounds good. I am not in Knoxville very much but if I get over that way I could definitely use another perspective on this thing. This morning I was going down the road and the a/c started working out of nowhere. I didn't hit any bumps or anything. I was travelling on a nice smooth stretch of county road at about 40-45 mph and all of a sudden I feel cold air coming from the vents. So, I pulled over and checked the a/c switch sense and it read exactly the same as it did yesterday when the compressor would not kick on. I also hooked up my pressure guages. It read almost exactly like the Chrysler FSM says. The low side cycled between approximately 23-43 psi and the hight side fluctuated between around 185-200 with the outside temps at 80-82 degrees. And, it was blowing 40-42 degree air with a thermometer in the middle vent. Nothing seems to be different than yesterday when the compressor would not kick on without me manually cycling it. I'm baffled! Any suggestions?

 

it seems like an intermittent switch failure to me or a broken wire somewhere in the ac sensors. have pulled wiggled or disturbed any of the wiring to any of the sensors?

 

Yeah, I have pulled the switch from the dash and I have spent the last two days tracing wires.