Air conditioner problems

[fritzimax]

Hello, it's HOT up here in New York and this is now my third summer without a proper working air conditioner. Right now if I ground out my compressor relay the clutch engages and I get cool air. I have to cycle the compressor on and off manually to get some cooling.
For some reason that no one can diagnose why the compressor relay is NOT getting the ground signal from the computer. If anyone has any ideas it would be greatly appreciated. Just a note pressures are within specs, and the pressure switch and realay have both been changed.
I thank all who reply.
Pete

 

[Prairie Dog]

Check for codes, especially anything regarding clutch fan stuff. If it shorts the bus then it will cause all kinds of problems.

 

[gtobey]

Prairie Dog and others are onto something. Reading the service manual, have they used the scanner to check for codes such as the B1001-A/C switch request input circuit low? Here's what it says about that:



The A/C mode switch input changes when the switch is pushed down. A stored DTC B1001 indicates that the A/C

mode switch was stuck in a pushed position for more than two minutes, but has since returned to its normal state.

An active DTC B1001 indicates that the A/C mode switch is stuck in a pushed position. An active DTC B1001 will

also prevent proper A/C mode switch and status indicator function as evidenced by not being able to turn the A/C

status indicator either on if off or off if on.

² Set Condition:

If the A/C mode switch stays in a pushed position for more than two minutes. This DTC has a maturing time

of two minutes and a de-maturing time of two seconds. If the DTC's status changes from active to stored it will

stay in memory for 100 ignition cycles.

Possible Causes

A/C HEATER CONTROL DAMAGED

OBJECT HOLDING A/C MODE SWITCH IN A PUSHED POSITION

SUBSTANCE CAUSING A/C MODE SWITCH TO GET STUCK IN A PUSHED POSITION

A/C HEATER CONTROL

Diagnostic Test

1. INSPECT THE A/C HEATER CONTROL FOR DAMAGE

Inspect the A/C Heater Control for damage.

Is the A/C Heater Control damaged?

Yes >> Replace the A/C Heater Control in accordance with the Service Information.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL

MODULES - STANDARD PROCEDURE).

No >> Go To 2

2. INSPECT FOR OBJECT OR SUBSTANCE CAUSING THE A/C MODE SWITCH TO STAY OR STICK IN A

PUSHED POSITION

Inspect the A/C Heater Control for anything that would cause the A/C mode switch to stay or stick in a pushed

position.

Is anything present that would cause the A/C mode switch to stay or stick in a pushed position?



I didn't notice if they had questioned the controller on the dash. Checking codes will tell you if there are problems with that part of the system. Sounds like you covered all the others...



Let us know what you find...

 

[JJPage]

Here is a possible cause...
http://www.dieseltruckresource.com/dev/showthread.php?t=81936

 

[fritzimax]

Well it has been a long time coming but finally my AC is fixed.
After three summers of no air conditioning on my truck (once the engine warms up) on advice of my mechanic I sent my ECM to a place in Massachusetts to have it tested. I received my ECM back and no faults were found. My mechanic still insisted the ECM was at fault so I purchased a refurbished ECM from a place in Florida and guess what my air conditioning works once again. The ECM sent to me was preprogramed and was plug and play. I contacted the company who tested my ECM in Massachusetts and they issued me a refund for my test fee.
As it turns out there is a relay in the ECM that sends the ground signal to the AC clutch relay, once the engine/ECM warmed up the relay would fail. I am happy to have a functioning AC again (though I don't need it this time of year) but it is not without a small issue, with the refurbished ECM installed I get error code P0602. I hade the code cleared but it comes right back. I have driven the truck for over a week now and everything runs fine, actually I think the truck runs better now than before the swap. I have done a search and many people tend to say not to worry about the P0602 code it is common with an ECM swap or a reflash, I hope they are correct.
Happy Holidays to all.

 

[cerberusiam]

Mor than likely the root cause is your lack of a PCM that is causing that code. The ECU flash you have is looking for the PCM communications and since it isn't there is setting the code. Since all the PCM on the 03's does is control the transmission it is not needed so function is not impaired in how the engine runs. That partticular code can have multiple meanings depending the version of software and ECU number. If it doesn't cause a constant CEL and interfere with the operation, probbaly not worth chasing it.