Heater staying powered up

The heater on my car stays powered up even when the key is out everything works when you put a meter across the ign switch power is behaving as it should in the wiring diagrams it shows an aux relay which is the next port of call but where is it and any ideas what it looks like?

Phil …

I’m a little confused (which is perfectly normal). You say your heater works even without the ignition being turned on.

Do you mean the two circulation fans continue to run even with the ignition key in the off position. I doubt that the heater is working without the engine running and pumping hot water through the heater core.

The engine simply pumps hot water through the heater core matrix. Depending on the year of your car (you should add that to your profile or include it in your post) you may or may not have a vacuum operated shutoff valve on the inlet hose going to the heater core matrix. The two fan units then blow air through the matrix (which heats it) into the cabin. This air path is selected by the two blend doors operated by stepper motors controlled by the air conditioning ECU.

Issue has nothing to do with hot water the whole of the electrical side of the climate control is powered up even when key is out what im trying to find is the aux relay which is what powers up the climate control as ign has been tested and when turned off and key is out is off which suggests aux rellay which is energised by ign is sticking on but where is it? the car is a 94 year cheers

Hey Phil, Not had the issue myself (as yet :slight_smile:) but I remembered something about the auxillary relay being discussed on another forum …

After checking out that old thread saw this reply, hopefully it will lead you to the solution!

FIXED. It was the yellow relay DBC 10009 under right dash. This is the auxillary power, side light power and cigarette. I have notice times when climate control and radio not work after starting car. would usually turn car off and on. It was not the ignition. Also, my side lights an tail lights work about 10% of the time. Got pulled over one night a year ago so I always just leave the rear fog light switch on which suffices (but unfortunately not for the side markers). The blower receive their power from this AUX relay too. A few taps of a screwdriver handle and BINGO. lights on. Same if radio goes out.

cheers

Larry

Phil …

So we’re not talking about the heater anymore, you’re saying your climate control PANEL remains energized even with the key off ?

thank you for the information but it might of made things worse as i dont have issues with anything else just anything to do with the climate control.

anything to do with the climate control/heater that is powered up electrically stays powered up with ign off and key out

The relay, DBC10009 with the yellow base serves FOUR functions, it is really 4 relays in one.

“Auxiliary positive”, Sidelight positive”, Auxiliary sidelight” and “Cigar lighter”

3 on ebay right now, around $20-$30

“Auxiliary positive” is the portion that may be hooped on your car.

Larry

Larry Thank you at least now i can progress but i have now found that if the battery is disconnected and reconnected the climate control works properly until its been on for about 30mins then it plays up and stays powered up thanks again
phil

Hi, I’ve had to replace that same box last month. They are not available new as far as I know. Before you fit a used replacement you should open it and carefully inspect all of the soldered joints on the rear of the board, especially the pins from the relays. The solder cracks around the pins, it seems to be a common fault on this control unit.
The used replacement I bought also had the same problem and needed those joints re flowing before I could fit it.
As it’s very easy to access and remove, maybe you could just check and repair the one fitted and save the cost of what could potentially be another faulty replacement you’d have to repair anyway.
good luck

I also forgot to mention that the problems caused by those cracked solder joints can be very intermittent, sometimes everything works well for hours or even days before the symptoms come back.