There's something up with my A/C. When sitting at idle, it works fine, but when I get moving down the road, it is worthless. It had enough freon, but was on the low end of good, so I recharged it with an auto store can this weekend, but that didn't help. Is there some kind of sensor or safety switch that could be killing it when I am driving?

jeepme79's Sig:

2003 2500 4x4 QC SB 6-sp, BD Triple Dog
318,000 on the clock and counting.

We have several dudes here that are A/C techs...........one of em will check in with answers

Whit's Sig:

* 01 Cummins/Dodge/HO/6 speed*275 injectors*PDR 35 turbo w/14cm housing & high pressure boots*HTT 3 piece ported exhaust manifold*Progaurd 7 with prefilter*Edge Comp*Fass II*Southbend con OFE*Jacobs brake*5"Stacks Big ens*E/F shift knob w/2low & brake switch*10 Gages*KW Ram air System cab controlled*Rickson 19.5x265's*True speed calibrator*Rancho 9000's*DT track bar*DSS steering stabilizer*KW Side impact rails*KW Traction Bars*Toolbox/fueltank 60 gal Combo*Mag High Tech Diff Cover*Ranchand bumpers*Grover air horns*Rear Wheel Cylinder Upgrade DYNO 375 Horse 941 Torque

“Life is not about waiting on the storms to pass…it’s about learning how to dance in the rain.”

Well, after testing a few different scenarios, here's what I have...

1) When I first start the truck and take off, I get cold A/C for about 5 minutes, then it is as if I shut the A/C off and am running just vent
2) When it is working, it works in both fresh-air and recirc mode.
3) When it is cold, it is cold on both L and R sides, so that doesn't seem to be the problem.
4) After the A/C dies, if I shut it (air) off for 5-10 minutes while going down the road, then turn it back on, it will work for a few minutes, then stop.

The A/C works, but something is causing it to shut itself off. I don't know if it is a sensor, preasure, freezing, or anything else. I ran a parts store recharge can with a guage. It was a little low, but not enough to make a difference so freon shouldn't be an issue.



A little update for tonight, I checked the codes tonight and saw a "P0647 A/C Clutch Relay Ctrl Circ Hi"

Could it be that at the higher rpm's the A/C clutch is still grabbing hard and turning too fast?

When you added the freon did you have a set of gauges hooked up so you could check the pressures? When you added the freon what the truck running with the A/C on? It kinda sounds like the high side pressure switch may be bad. If the system starts to build too much pressure it will shut the A/C off so the system won't rupture.

Another thought, is your can clutch engaging when the A/C is on? If not this could be the problem as well. What the A/C is on the fan clutch should engage. This makes the fan work so it pull air across the accumulator which keeps the pressure from building too high within the system.

Buckshotmckee's Sig:

U.S. Navy Seabee Veteran


"We Build, We Fight, We Drink More Beer!"

my ex had a problem with the vaccum sensor/pump( whichever they have it was a year ago) in his dodge that caused the a/c to not work properly ( also the 4wd would not work) but he totally broke his maybe urs if you have one is just malfuntioning? it was broken during the installation of his edge chip believe it or not which the people who did it said wasnt possible. im not sure if it applies as his was a 2nd gen, but i thought i would mention it just in case, i culd be totally off base but if i mite have given an idea i thought what the heck . ne ways hope u get it figured out.

dieselgrl4life's Sig:

2006 Dodge Ram 2500 Cummins, Big horn edition, 4" turbo back straight pipe exhaust w/ 6 in tip ,turbo silencer ring MIA, Quadzilla Max Mileage M3, From Holland Court Diesel: Icebox cold air intake, TorqueTube and Intercooler boots, 34" x 11.50 Maxxis Bighorn Mud Tires "Blowing Smoke Gang- Administrator/Scout/Ladies Section President and the Official Model for BSG"

If I recall, on the 3rd gen trucks, Chrysler got away from vacuum actuators? Everything is electrical.

i thought sumthing lke that might have happened but i thought id mention it any ways, sry guys.

I did have a guage on the freon can, with the A/C running on max when I put it in. I ran it up to the high end of the "OK" mark, so it shouldn't have too much in there.

I don't recall if the fan kicked in or not. I can feel the compressor kick in, but once it shuts off, it doesn't come back unless I turn the A/C off for a few minutes.

i have a similar problem with the ac unit on my 06 cummins, the ac works great while im driving my truck but at an idle i have no ac. the fan kicks on but will I will have nothing but hot air blowing out of the vents, anyone have any ideas?

It sounds like an electronic problem on your 06. In 06 chrysler went to a CAN-BUS system. Everything is tied in.

I have no idea how this relates, but the day I removed the Edge Juice/Attitude, the A/C works perfectly. After 10 minutes, I actually have to turn the temp up a bit because it is too cold.

Sounds like the evaporator cooler is icing up, when it does this do you notice if the a air comming out of the vent is not blowing as hard as when you first turned it on? If so then thats the symptom of icing. Also you may not see water condensation on the ground. This may be due to a clogged condensation drain. My dads truck does the same thing and I turn the heater on to de-ice it.

Voodoo Trucker's Sig:

94 Dodge 2500 2x4 11.06 @ 128 mph http://blip.tv/file/709749

I do HVAC, and it sounds like it is low on freon. You need a set of gauges, not what they sell on the bottles. Those are mostly WAY inaccurate. If you can get a set with long hoses, check pressure at idle, and going down the road. The best temp is 80 degrees, but that isn't too big a factor.

puddlestomper's Sig:

2004.5 Chevy 3500 dually 2x4-not running
another 2004.5 3500 dually 2x4 -also not running---Accepting donations of knowledge
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my a/c went ka-put monday am the compressor will not engage and in GA it is 100 deg. in the afternoons and too flipppin' hot to not have a/c for an hour commute. any suggestions

anyone know what the three wires go to on the preassure switch on the a/c goto?

i am not used to seeing 3 only two don't know which one to jump to check the switch.


this whole idea of no a/c in the afternoon stinks realllllly baaad!

any help would be appreciated.
Thanks