Hi all,

It appears the small fan which resides behind the automatic temperature control (ATC) module in the dash of my 2000 LHS runs when it should not, and therefore will kill the battery in pretty short order (to the point where it can't be jumped, after sitting for about a couple of weeks or less). The way it happens is as follows - if I do not arm the car alarm when leaving the vehicle after the engine has been shut off, this motor will run even with the ignition shut off and the key removed. However, if the car alarm is armed, the fan shuts off.

Has anyone seen this behavior? A short or fault somewhere? I've gotten around the issue by disconnecting the fan motor from the ATC, but this means the automatic setting of the ATC does not work properly. Not a big deal, but I'd like to know the cause. I have replaced the ATC due to the notorious cold solder no display issue, but the constantly running fan issue remains.

Thanks for any help.

Chris

 

blower motor resistor is keeping the fan on

 

Thanks for the response. Just to be clear, are you saying a faulty blower motor resistor could cause the interior ambient temperature sensor fan to run constantly? My understanding (maybe wrong) was that the blower motor resistor affects just the blower motor.

Thanks,

Chris

 

Lets see if I can explain this.

What makes you think the inside infra red temp sensor is keeping a fan on when the system is turned off? What does the temp sensor do? tell a computer what teh temp is inside and then it makes adjustments to the blend air door motor and the ground control the blower motor resistor to control fan speed when the system is turned on?

Its not a simple resistors its actual name is a blower motor power module.

 

OK, now I'm going to see if I can explain, since I don't think my actual problem is understood.....the problem is not with the blower motor. There is a *tiny* motor which is attached to the inside of the Automatic Temperature Control module (the display above the radio which allows you to adjust fan speed, temperature, turn defrost on and off, etc). My understanding is that this tiny fan allows ambient air to be drawn over the ambient air temp sensor (which is a thermistor, not IR) which sits directly in front of this fan behind a small grill directly underneath the fan control ****. I'm sure the computer somehow controls when this fan should cycle when the controls are set to auto, but I'm also sure this tiny fan is not supposed to run at all when the key is in the OFF position or removed entirely. It is this tiny fan running constantly which is eventually killing the battery. If you're saying that the blower motor power module could account for this behavior, it wasn't clear to me from your explanation. If this is something else though, what could it be? An electrical fault of some kind? One thing I haven't tried is a re-calibration of the climate control system.

Thanks,

Chris

 

ok no that tiny fan wont draw enough amps to kill a battery over nite

OF you think it is unpluf the ATC head and see if your draw goes away.

 

The draw comes over the course of several weeks, since the car is not used often (you can actually hear the fan running). The last time it happened, car hadn't been started in about a month and even a jump would not start it (brand new battery). It took a charger to bring the battery back.

Unplugging the fan from the back of the ATC unit solves the issue of the fan constantly running (and thus the battery dying). I guess if I have to, I'll keep it disconnected and just not have auto temp control (I think). Would still be nice to know the source of the issue.

Thanks,

Chris

 

the fans power comes right from teh ATC module so id say something in the module is keeping it on.

 

I thought maybe the ATC was the culprit too, but that was replaced for a display issue and the fan behavior continues. I'll report back after trying the recalibration, which won't be for another week or so.