QuestionQUESTION: Blower runs on high through defrost vents.
Atc module is unresponsive when that happens.
At this moment ATC control module is removed.
BCM is unplugged & blower is still on high.
There has never been any heat with this car and the code
readout refers to blend air door.
The other problem is the radiator fans run full time even when the car is cold. Once in a great while they will stop.
Thank for any help you can provide.
ANSWER: Hi Dave,
The blower remaining on high usually means that the blower motor power module is defective. That is located in the air duct just downstream from the blower motor; trace the wire from the blower motor back to find the module. Once you deal with that you should regain control of the blower motor multiple speeds. It is a solid state device so you probably will find it most economical to go to a wrecking yard for a replacement.
On the radiator fans, I would wonder if one of the two fan relays is fused closed. The two relays are in the back of the power distribution box under the hood, the two on the driver side of the rear row of four relays. Test both relays to see if they are connected from the front pin to the rear pin of the relay or not (B to D, if labelled); there should be no connection from B to D if the relay is good. If neither is bad, then we have to figure out why the pcm is activating the fans, unless of course you have selected AC which automatically turns on the fans no matter what the temp of the engine coolant.
On the lack of heat, that would suggest that the code is correct: either the blend door is binding or the door actuator is not moving it.
It is possible that the ATC module has some problems, but assume otherwise until you verify the above.
Roland
PS Use the "thank/rate" tab below to get back to me without having to wait for me to be 'available' to take a question. There is a space for comments.
The relays for the radiator fans seem ok. Do you have any other ideas about why they run full time? Dave
The relays are activated by the pcm: the low speed by its grounding pin 32, the high speed by grounding pin 31. I would check to see whether one of the wires from those pins to the relay socket could be shorted to ground. Pull the pcm plug and the relays and test for a short to ground. If the wires are not grounded, and the fans I assume don't run with the relays pulled out, then the pcm is either grounding them due to an inaccurate signal from the coolant temp sensor, or the ATC is telling the pcm that you asked for AC falsely and the pcm thinks the engine is warm as well, or the pcm is faulty. I would wonder if the coolant temp sensor is off value? Measure its resistance to ground when the engine is cold and warming and hot. It should move from 7-13k down to 700 ohms during that transition.
Thanks for the kind remark and nomination. Please let me know what you learn. Did the blower motor come back under control?
---------- FOLLOW-UP ----------
QUESTION: Hi Roland,
I did try another blower motor power module, but that did not correct the problem. When I finally figured out where the blend air door was, I found it was stuck. After freeing it up the blower started working normally. I had also picked
up another blend air door actuator just in case. With the actuator removed but still wired I thought the shaft should turn when I turned the temperature control up. Neither unit responded so I thought they were both defective. I then ran atc module self check and the shafts on both units turned.
Just thought I'd pass that on. The problem with the radiator fans is still there. The coolant temp sensor seems ok but I will replace when I can. The relays seem ok. I've pulled the fan high speed relay so at least the fans are running on low speed. Thanks for all your help.
Dave
AnswerHi Dave,
Thanks for that progress report. I don't see why the blend door malfunction would impact the blower motor speed unless the feedback loop was disabled by the actuatior/door. I'll be interested in the fan control issue when you get to it.
Roland
Hi Dave,
I was wondering if you solved the radiator fan issue, or if you still needed some help?
Use the 'thank/rate' tab below to get back to me if so. And while you are there if you would consider entering a 'yes' where you see the question about a "nomination of me for expert of the month" I would be most appreciative. Thanks in advance.
