I have a 2006 3500 dodge mega cab cummins deisel. air started not cooling after startup about half the time. then didn't work at all unless i waited untill speeds of 60 mph or greater, then worked when i slowed down after that. first diagnosis was the high pressure switch, ran jumper wire from battery to under fuse panel worked for one day then same ole same ole. hasn't cooled since. now they are saying its the computer. truck has 70,000 miles. what's up?
The first step is to power wash the condensor . bugs, dirt, and road grime are most likely obstructing the airflow over the coils(this would explain it cooling at high speeds). next check to make sure your a/c clutch relay is good and not weak(if it kicks in and out all the time before it's been running awhile it could indicate a weak relay or an undercharged system. next evacuate the system then replace the dryer.(if the dryer is clogged this would result in it running for a bit but then shutting down. next recharge system(make sure the pressure for lowside is 35 psi and on the high side 120-150psi for a 134a system.) next if this has not solved the issue chances are that your expansion valve is junk(this regulates the 134a in the system) the high pressure swith(also called a binary swith only works with the expansion valve in regulating the system and if you don't have a high pressure let's say like 250psi or more in the system on the highside.( very seldom will a computer be the problem in a vehicle that is not that old. one last thing i should mention is that you have a blend air system(srevo motors control doors that regulate the cold air and hot air from your heater core) if these are not operating properly the door could be open over your heater core too much and it's blowing cold air but you would never feel it. you also have a climate control module. that be checked as well. a good mechanic will check all these things before pronouncing the usual answer if they got no clue..."it's the computer" hope i gave you plenty of options to solve the problem....good luck.......please rate this..........thanks
06 model year had a problem with the recert door braking and falling down on the fan,pull the fan and stick your hand up in the hole and see if its laying there,also the megacab is bad about no flow,to corect this problem the dash has to be removed
If it is the pcm...the pcm is covered under a federal mandated 8yr 80k warranty...tell them to replace it...its free....past that without pressure readings and such it may be hard to diagnose
As
per your problem mentioned. There are few solved help links to
troubleshoot these problems. Go through the list and Click the link below:----
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http://schematicsdiagram.blogspot.in/2012/02/heater-blows-cold.html
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http://repairhelpcenter.blogspot.com/2012/01/hot-air-on-drivers-side-vents-only.html
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http://technoanswers.blogspot.in/2012/04/1992-toyota-camry-ac-control-light.html
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These will help.
Thanks.
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