downlow

Okay when I bought the truck the a/c didnt work. The dealer put on a brand new pump this was at 90,000 miles, the same time I bought it from the lot. I had no luck getting it to work then now Im trying again. I shorted both pressure switch's to no avail, the only way I get it to work is bypass the relay on the fender but then the pumps stays on, then freezes up the system.
Could I have a PCM issue instead this whole time? Where is the pcm? Thanks in advance!!!

dodgeguy71

If it comes on by jumping the relay it could be a low pressure switch not letting it come on. I know you jumped the switch but sometimes these things don't work how you would think. And bypassing the relay may have something to do with why it will not kick off at higher pressures and freeze up. I've bypassed a few in my time and they will run and run while I watch the gauges and the compressor will not kick off automatically and would likely run for all eternity if I were to let it.

Have you put gauges on it to see what the pressures are? Did the guys that replaced the compressor actually know what they were doing or did they have a diagnostic shotgun in their toolbox? Which led them to the compressor replacement? If you are unsure of the amount of refrigerent in the system this could be a problem if it is actually........low, which would be why it won't come on. Seen it before some hack shop fixes a persons caddy and then it ended up at the dealer where I hear the story of how they had it at joe's hack n' shack cause he was cheap, ding's them mega bux and it still don't work. Joe's scratching his head and customers ticked, I have to figure out what Joe did.......yippee.

Anyhow, you need to know that you have the right amount of refrigerent in the system. Then you'd need a good schematic so you can figure out what is doing what and where.

downlow

Sounds like sound advice to me...Ill get some gauges and check the thing, then switches..thanks for reply!

starflite3

Downlow,
I said I would get my A/C fixed and let you know what I found.
Well, after I read the schematic in my shop manual I found out why I had continuity from the relay to the comp. and the comp. would not run. When reading cont. from the relay to comp., you actually do not read through the high and low pressure switches. Relay wiring goes directly to comp. High and low pressure switches are on the control side of the relay. IT WAS MY LOW PRESSURE SWITCH!!!!!!!!!!. Man!!!! I assumed (you know what that leads to)that if you could read from the relay to comp. the switches were good. Wrong!
I don't know what I was thinking.
Anyway, this is all after I had replaced the comp. and it would not run when I had 70+ lbs. on the low side.
If your evap freezes up you probably do not have enough refrigerant in your system and when you make it run it freezes up. Or, maybe your condensate drain is plugged. Or, maybe your evap is full of squirrel leavings. Insufficent airflow across the evap would make it freeze up as well. I would check these things.
Like Dodgeguy said who knows what has been done or not done to your system when the comp. was replaced. Did they even evacuate the system? Did they check the pressure on the high and low sides?


My Dodge shop manual says pressures at 80deg.F ambient should be:
Evap press. at charge port - 32-40 psi
Comp. discharge press at service port - 190-220 psi.
Air temp. @ center panel outlet. - 33-44deg.F
I am not quite there, little more tweaking to do tomorrow. Had to quite for tonight.

Hope this helps.

downlow

^^ Your reply is greatly appreciated and your going to love this story. I did a few more checks/tirals and still no go. I needed to send the truck for a front end alignment so instead of buying guages and hunting down a schematic I told the wife to just "have them take a look at it." The mechanic there is reasonable and Ive never had an issues with his work, normally I do it all myself but after 5yrs of indecision on what to do I said the hell with it let them try.
It was a fuse!!!???? Well the lid over top my relays and fuses under the hood is mislabeled. The fuse that runs it is labeled "horn", well after shortening up a Cavailer by a foot and half one day I knew those hrons didnt work and I knew the fuse was blown...errrr.....The guy said he was confused becasue it didnt make sense so he looked up shcematic or found the correct way the thing is suppose to be labeled and it was the horn fuse....yeah real nice ehh....
Front end alignment and fixing my air cost me $85.00, now that's cheap. Maybe I owe this guy a six pack.

heykw

The horn and A/C compressor share a fuse.