My 98 Ram has a great air conditioner. That is until I hook to my camper. It then works fine until I hit the highway. It works fine through town, but once I get on the highway, the compressor kicks out and won't kick back on. Sometimes, when I take an exit or come into a town, it might come back on until I hit the highway again. But, most of the time it won't come back on until the engine has been turned off for about 10 minutes or so. It will work just fine, nice and cold, until I get back on the highway. This only seems to happen when I'm towing my 6,000 lb camper. The truck has plenty of power to pull it, doesn't seem to work anything too hard and never tries to get hot. Any ideas?

 

There is a relay somewhere that sends power to the compressor when the control tells it to. The question is if the relay is getting signal from the control when the problem is occuring but not turning on. If it is then the relay is bad and needs replaced. If not then there is something wrong with the control. You'll have to do a little troubleshooting to figure out what is happenning. It sounds like it may be in the control though.

 

How is the temp door controlled? Is it just running out of vacuum, and switching to warm air?

Are you sure the compressor isn't running? I could never tell on a V-8 motor on the freeway. (my four cylinder on the other hand.... you could really TELL when the compressor on that one kicked.....)

 

Do you have a trans temp gauge? I wonder if the trans is getting hot and the PCM is kicking the AC off to allow cooler air to the radiator and trans cooler. I have no idea if it actually can/does do this, just a thought I had.

 

I think the compressor isn't running because the air coming out of the vents is not cold...at all. It is just like it is on "vent" insted of "A/C".

 

**Update**
Looks like the camper may have nothing to do with it after all. Because, it cut out today without the camper not even on the highway. Just riding around in Pigeon Forge, TN. After it sat for a few hours in Dollywood's parking lot, it has worked just fine all afternoon long. I'd love to figure out what's causing this. It's gettin' hot in Tennessee.

 

When My 98 goes into over drive with my 35" tires, mine sometimes goes to defrost. ( drops vacuum ).

 

Yeah, mine has done that since it was brand new. The dealer put a little one-way vacuum thing on it, but it didn't help at all. I can live with it going to defrost under a hard pull. But now, the compressor just takes spells of not clicking on. I just towed my camper 100 miles, and the A/C worked perfectly all the way. But just yesterday, the A/C only worked for a few minutes of the 2 hour trip. Maybe a switch? I checked the plug connections at the dryer and the compressor. Looked fine. I bought this truck brand new, so I know that nobody has been under the hood with a Barlow and black tape. All of the elect and A/C lines look just like they did when it was new.

 

Could be the switch, or one of the pressure sensors. I suppose it could be the compressor clutch itself. One of the times it dies, pull over and start checking for power with a test light.

 

Yep, that was my next step. The next time it quits, I'll pull over and test the wires going to the compressor w/test light.