My 2001 Convertible suddenly lost heater function. It has gone to defrost mode with no heat, blowing cold air out of the defrost outlet. There seems to be no response from the temperature dial or the mode dial.
Is this a body computer problem? I hope not.

 

make sure u have coolant in the system most of the time they leak out.

 

I'll check, but why would the mode get stuck on defrost? And when I checked yesterday, the heater hose was hot, leading me to believe there was hot water in it.

I just checked the coolant level. It's up. Any other sugggestions?

 

The controls for the heater/defrost system are vacuum controlled. If all functions have failed simultaneously, as it appears you are describing, then a vacuum supply line is likely to be cracked, kinked, off, or otherwise malfunctioning. Could be under the hood, or the dash. Try under the hood first.

 

incorrect info any new body style from say 99 and up does not use vac ne more all electrical servos. The defrost issue could be the BCM, wires or the accuator it self is bad.


REMOVAL NOTE: Prior to part replacement, re-calibrate the HVAC actuator. With vehicle running: [ul][*]Place mode to defrost on HVAC control.[*]Set temperature to full cold on HVAC control.[*]Set blower speed to any speed except off.[*]Hold down the EBL button until chime is heard. The system will then perform a calibration which takes about 60 seconds. [/ul] [ol][*]Disconnect battery negative cable.[*]Remove left silencer panel.[*]Remove wiring connection from actuator.[*]Remove mode actuator (ACTUATORS) mounting screws and pull actuator straight down. Note actuator shaft position for installation reference. [/ol]




[IMG]local://upfiles/1033/9076A25B0C0A47F5AC52725C583A32AF.gif[/IMG]

 

Thanks for the input. I ran the calibration procedure you suggested, and error code "AC 46" showed up on the odometer. Where do I find out what that means?

The"no heat" problem has taken to coming and going. It will be there sometimes and go away sometimes.

 

Latest report on the ongoing saga of the malfunctioning heater: Last night (when I really wanted it to work) it went out again. This time, it was dark out and I noticed that the light in the unit was also out. I tried that calibration procedure, but there was no response. The calibration procedure requires input from the mode switch, temp switch and rear defrost button. None of those controls produces any kind of response. With the light out, it now appears that every function controlled by connector 1 is non-functional. Today I'll pop out the unit and check that connector but last time I was in there it snapped on quite nicely so I doubt that's the problem. It seems to be coming down to a problem with either the control head or the body computer. Is there a simple test of the control headto prove that out?
I hate to replace the body computer as it's a big expense and without a DRB tool I can't do it myself.
This car has the sentry key option so if the body computer is replaced the car won't start.

 

unless u have a DRB the BCM sees the inputs from the ac control head and it woulld let u know then what the issue is either A the control head is not sending the correct signal or b the BCM is not getting it and changing the doors.

and FYI the BCM has nothing to do with the skim but commucation wise like with all the modues in the car. The skim is for letting the PCM know its ok to start and run.

 

Given that I haven't seen any malfunction of the BCM outside of these issues with the heater control, and in the absence of access to a DRB tool, I'm leaning toward the conclusion that the problem is morelikely related to the control head than the BCM. I might swap control heads with my '02 sedan and see if the problem migrates to that car or stays with the '01. If the problem goes over to the other car with the control head, then the control head is to blame. If it stays, then it's a BCM problem.
Is there any chance of replacing the BCM and having it work without access to a DRB-III tool? Used BCM's are available but my shop manual states that replacement of the BCM requires re-programming with the DRB afterward.

 

Final chapter in this story, I hope. I switched control heads between my 02 sedan and the 01 convertible, and everything worked except for the lighting on the old 01 panel. Turned out it was one bad bulb. The bulb is NOT what is stated in the owners manual and in the shop manual (#37) but rather is a special part with a long socket. Anyway, everything now works and I am going to leave it alone.