There's some pretty intelligent and knowledgeable people here so I figured I'd ask for some ideas. My mother has a 2010 Ram 1500 with the 5.7 and its been having A/C problems for quite a while now and I've been tasked with fixing it with my very amateur level skills. I'm not entirely sure WHAT the problem is because it's so inconsistent, what I do know for sure is that the engine computer has an uninformative, vague, and perpetual P0533 code (A/C Refrigerent Pressure Sensor "A" Circuit High) that I can't clear. When the compressor does run I get pretty decent pressure readings at least according to my A/C chart. at 70F I get 30 psi low pressure, and 131 high pressure, which if anything seems a little low but compressor doesn't short cycle and the air blows ice cold.

After looking around I haven't found much on this, I heard that the coil can sometimes draw too many amps that the computer doesn't like it and shuts it down. I've replaced the clutch and coil and unfortunately no difference.
I checked for voltage at the transducer and it's getting its 5v reference signal, replaced it anyway with no change. The electric fan does run when the compressor is active and the pressures remain stable according to my cheap amazon gauges. No blown fuses.
Resetting the battery worked for about 15 minutes before it stopped working again. Resetting it a few more times worked but at one point stopped working all together.
I've posted on other forums before with no responses besides one person mentioning the controls in the dash is a module that he's seen go bad before, but I'm not sure how to test that and it seems to work fine and lights up and when the compressor runs it commands it on and off just fine, I figured if it was busted the compressor wouldn't run at all so im not sure about that. I also heard that the relay is built into the computer and can sometimes go bad, is there a way to test that?
My mother says it started working last night again when she went to the store. So I'm really scratching my head with how intermittent this issue is. I don't know but it almost seems to work better when it's cooler outside? (which sucks cuz its hot as ***** here in Georgia lol.) It sounds like it's possibly a loose connection but everywhere I can check everything seems fine.
If anyone has any tips or advice on how to go about this I would greatly appreciate it.

 

Gonna need a service manual to sort that one out. Apparently, there is a "pressure transducer", that is 100% tied in to the TIPM..... seems there aren't any discreet pressure switches, like you would expect.... at least, not according to the wiring diagrams I have access to..... Generally, you can find service manuals for 30-40 bucks in PDF format in various places.

 

I have a PDF I downloaded although I haven't been able to get much from it, and the wiring diagram text on my PDF isn't readable which is weird... Do you think it's possible the TIPM itself might be faulty?

 

Entirely possible, but, an expensive guess.

Where did you get your manual from? It isn't real useful, if you can't read it.

 

Hopefully not lol but I'm unsure at this point. It started working again when I started the truck up and worked great for a while before it cut off, shutting off the truck and then starting it back up 20 minutes later made it work again and this happened about 3 times where it'd work on startup for a while but stopped working entirely after that.

The manual is from some older forum post someone shared it in sometime ago so I'm not entirely sure . I ought to just buy the right service manual probably.

 

Something gets hot, and fails..... Don't know if the relays in the TIPM in that truck are replaceable, or not.... if they are, that would be a place to start.

Yeah, get yourself a copy of the service manual you can actually read.

 

That does sound plausible. For a while I thought it was the evaporator icing over or something. As far as I know the relay for the clutch itself is not serviceable but I've heard people bypassed it by wiring in an aftermarket relay.

 

Folks do the same for the fuel pump relay.

Theoretically, there is a 'pressure transducer' somewhere in there, that reports to the TIPM..... That is also another possible failure point. Where it is on the 5.7 though, no clue.

 

There's one on the high pressure line on the passenger side of the engine bay, it just unscrewed right out and I put a new one in. Didn't seem to be the source of the problem unfortunately. I wonder if I can somehow get eyes on the clutch relay itself and see if it's cooking itself inside of the tipm? I'll probably find out when I inevitably touch it and burn my finger or something