TelBoy

If anyone can diagnose the below problem i'm having with my heater control, i'd be very grateful.

Mine's a 97 WRX 5 door, with aircon. When the temperature control is set to the coldest setting (i.e. "20"), the solenoid which controls the hot air flaps moves to the fully closed position, so there is no hot air getting into the car. No problems so far.

But, when i turn the temperature control just two notches warmer, the solenoid moves 2/3rds of it's range, so that a signinifcant amout of hot air comes in. To all intents and purposes, this means i have just two settings - too cold or too hot.

I've changed the heater control motor (the black box with the vent direction, temperature control and fan speed ***** on) and it does exactly the same thing. Last night i tried a different solenoid and it does exactly the same thing.

Does anybody have any idea what else might be causing this? I'm prepared to try anything so any advice/suggestions very welcome. Thanks very much,

Terry

Reg P

Hi, without the diagram or the car it is difficult for me to diagnose, but it sounds to me that the internal temperature sensor or the controller is malfunctioning. My understanding is that you set the temp you want and amount of hot air is governed by the solenoid, I presume the hot air control valve can move to any position and is not just on and off. If this is the case the controller should open the hot air valve initially and when the "setpoint" temperature is reached back the hot air off to keep the desired setting. I personally would look at the internal sensor first, depending on what type of device this is you can test it with a multi meter, I'll be happy to help further if required. I am not an auto electrician but an Electrical Engineer on an Oil refinery so the principles are pretty much the same. Hope this helps!!