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heater running when ignition switched off

1K views 6 replies 6 participants last post by  Eero H 
#1 ·
Hi folks. I recently acquired a 1992 e34. M5 (3.8) . When I brought it the heating was not working at all and the seller supplied a new fan with the car. So today I went to fit the fan but thought I'd check fuses first and on doing so I found one blown so changed it and now the heater is working as it should apart from the system to the heater is constantly live .. working without no ignition power being switched on ...

Just wondering if any one has had this problem and or any possible cause

Thanks . Jason
 
#2 ·
Jason,
One thought is a bad IHKR module. When it fails odd things happen. One way to check this is to plug in a known, working module to see if it remedies the problem. IHKR modules show up for sale on the forums for a reasonable price. Unfortunately, it is a commonly overlooked part by the breakers so they can be hard to come by. When I had a problem with my air conditioning it boiled down to a shorted out IHKR after three hours of tracing circuits!

If you have gotten around to changing the cabin filter then you already know how to get to the IHKR. If you have not changed your cabin filter, do your M a favor and give it a new one. While you're in there you can clean out years of debris that is not helping your cause.
 
#3 ·
Hi Jason,
I had this exact problem. It has to do with the programmable ventilation feature. There is a relay unit in the front passenger's footwell. This relay unit makes the programmable ventilation feature available. If you disconnect this relay, you will most likely solve the problem. The exact cause I have yet to find. The relay unit itself works fine in my case. The relay unit however receives s continuous signal from the onboard computer which keeps it switched on (and therewith the IHKA). So the likely culprit is the OBC.
 
#5 ·
what does IHKR stand for?
 
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