HVAC Control Calibration

Michael Owner/Technician Irving, Texas Posted   Latest   Edited  
2005 Jeep Grand Cherokee Laredo 3.7L 5-spd (45RFE)

It's Manual HVAC Controls.

A shop replaced the HVAC Box Assembly and all actuators click. Tried to perform relearn and the light never turns off to indicate that calibration has finished or indicates a failure (both lights flashing) with DTC's. Running a DTC check gives random DTC's when reset. From what I read only one current fault will sat at a time. 

I tested all circuits for an open, short to ground, and short to power. I ohm'd all actuators and they come out at about 36 and 37 ohm's.

All actuator are moving and click when the limits are reached.

Has anyone replaced an HVAC control for over current fault codes?

Original problem was a broken blend door and the complete box was replaced.

Caleb Diagnostician
Mishawaka, Indiana
Caleb Default

Check the current with an amp clamp. Of its good then I would say the problem is in the control head.

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Michael Owner/Technician
Irving, Texas
Michael Default

I don't have a current clamp for my scope, but I do have a power supply that measure amps I could connect and control the actuators. I went ahead and ordered a control head and it will be a week before it gets here. Maybe I'll see the customer before then and could run some more test.

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Keith Owner/Technician
Norwood, Ohio
Keith Default

Disconnect battery for 10 minutes if you haven't already.

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Cory Owner
Wichita, Kansas
Cory Default

which lights are flashing and what random codes are there? have you run a cold down test? the doors calibrate every time battery voltage is regained. the cold down test requires the ac to work and a 60 degree swing to pass so starting out with a HOT air box is helpful. the test is described well in mitchell and all data.

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Michael Owner/Technician
Irving, Texas
Michael Default

I haven't done a cold down test, since the Calibration never finished. I get random 40's codes (43, 44) and 50's (53,54). I have disconnected the battery voltage and it does run a calibration, but doesn't seem to finish either.

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Phil Technician
Las Vegas, Nevada
Phil Default

If the the car was built prior to November 28, 2004 it may have software that will display the wrong numeric value for the diagnostic trouble codes. (Technical Service Bulletin 24-008-04 Heating & Air Conditioning. DATE: December 18, 2004).

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Tanner Instructor
Wellford, South Carolina
Tanner Default

Find out if the box was replaced with OE or aftermarket. Also find out if any of the actuators are dorman. If they are dorman they won't create enough amperage for the controller to recognize the stops. I have had some problems with these through the years. This being an older vehicle I’m not sure if the Dorman actuators would be the updated ones or would still have that problem.

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Michael Owner/Technician
Irving, Texas
Michael Default

I noticed a Dorman actuator when looking at the actuators and it's the loudest one. I'll measure the currents hopefully next week before replacing the HVAC Controller.

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Michael Owner/Technician
Irving, Texas
Michael Update

Talk to the customer today and the new HVAC module didn’t fix the issue. He will be Louisiana for a couple of weeks before we can run some more test.

0 Update Ð Bounty Awarded