After searching and reading posts regarding AC problems, I have to post my specific symptoms, as I haven't been able to find anything dead on with mine.


I've been having an intermittant problem over the last few months where the AC will just blow warm air out, and then outta nowhere it'll blow ICE COLD air.

I noticed that the AC Compressor is always off when it's not blowing cold. So I moved around the AC relay and swapped it with the horn relay. AC worked fine for a bit but then still did the same thing.

I noticed recently that when at idle at a light, or just decelerating that the AC will start to blow warm again. Then when I accelerate from a light that the AC will get ICEY again.

I had my Dmax idling in front of my garage with the AC switches on, but the compressor clutch not kicking in. I tapped the low pressure switch to see if the clutch would kick in... nothing.

I tapped the high pressure switch above the compressor and as soon as I tapped it the clutch kicks in and the AC works great now. I haven't had a chance to see if it'll stay on after driving a while, but I'm now lead to believe that the high pressure switch might be the culprit.

To swap the high press switch out, will the system have to be evacuated and refilled?

Thanks in advance for all help.

Search, there is much already on this!

http://www.dieselplace.com/forum/showthread.php?t=248937

http://www.dieselplace.com/forum/showthread.php?t=246514

Thanks for your reply.

I did search as stated at the beginning of my post. I was unable to find a post with symptoms the same as mine.

I read both of the threads you posted, and although somewhat similar, not quite what mine is doing.

The search for answers continues.

I would start by unpluging the electrical conection and cleaning up the terminals. If that did not fix the problem. Call the dealer and find out if there is a shrader valve inside of the high pressure switch port. If all elts fails loosen the fiting a couple of turn. If it has a schader it will stop leaking.

Check the air flow through the radiator stack and see if the fan clutch is letting the fan move air at idle. Take a big box fan and place in front of truck while idling and see if that keeps the compressor running. You can even let a water hose run on it (the condenser) at idle. Did you buy the truck new? Has anyone worked on the A/C? Its either overcharged with refrigerant or the radiator stack is plugged or the fan clutch is bad.

Speaking of the fan clutch....

In the mornings when I take off for work, sometimes I hear the fan blowing like crazy, as if the fan clutch is locked hard. Other mornings it first drives off normally with no excessive fan noise.

That has always led me to believe the fan clutch might be going as well.

I bought this truck used with 52k. I don't know much about it's history other than it was in for PCM/ECM reprogramming and Glow plug reprogramming at about 4k miles. It also had a new heater/ac control panel put in at 43k.

Waxerk5:
I did not see that you searched, but now I do. My bad on that issue. As far as the clutch fan goes, what you describe is very normal. It sometimes races until you reach about 30-35 mph or so, and then it should release and free up. Normal condition by much more than a mojority of members. I would think that the last thing you mentioned is where I would start 1st. Maybe the wiring on the panel is loose or something?

Speaking of the fan clutch....

In the mornings when I take off for work, sometimes I hear the fan blowing like crazy, as if the fan clutch is locked hard. Other mornings it first drives off normally with no excessive fan noise.

That has always led me to believe the fan clutch might be going as well.

I bought this truck used with 52k. I don't know much about it's history other than it was in for PCM/ECM reprogramming and Glow plug reprogramming at about 4k miles. It also had a new heater/ac control panel put in at 43k.

10-4, thanks.

I'll take a look at that panel and see how it continues to perform.