Folks I have been trying to diagnose a problem with the climate control on my 98 M3/4 and so far have not been able find anything using search or on the internet. The climate control blows full hot all the time. I can regulate the fan speed, but no matter what I set either the driver or passenger temperature to, the vents blow very hot air. I have confirmed by feeling the hoses that the two heater control valves are open. I know these can stick in the open position, but it seems unlikely that they would both fail at exactly the same time. I have also checked the values of the air temperature thermistor in the IHKA unit. They measured 15kOhm@32F, 7.9@71F and 6.6@98F. Those seem reasonable. Also, the symptoms do not seem consistent with the well document .47uF capacitor failure - all other functions are working. So my questions is, without having a diagnostic tool, is there a way to find out if the valves are being TOLD to open by the IHKA (I tried to call up the IHKA diagnostic codes by pressing the "AUTO" and "rear defrost" buttons, but that did not do anything). Any suggestions would be appreciated. Dave 98 m3/4, 103000
I am assuming you have the automatic climate control system in this car. If at all possible I try to switch your unit out with one that is known to work properly. It could be the control unit that failed.
I would assume that your heater valve has failed or that the heater valve is not being told to close (it defaults open with no power or ground to it.)
Thanks for the suggestion, Yes - the IHKA is the automatic climate control, and alas, I have no source from whom I could borrow one. Regarding the valve- it would seem that its the valves, but as I said, I think it would be unlikely for both the passenger and driver control vales to fail at exactly the same time. I was hoping for some sort of diagnostic test that could tell me what the IHKA was telling the valves to do..... Dave
The plug on the valves has 3 wires. One should be power with key on (IIRC) and the other two are the ground signal from the IHKA to close. If you are handy with a DMM you can check this yourself. You should have ground to both valves with the IHKA set to cold. If you have power and ground, your valves are bad.
Paul, Thanks for the tip. I measured the resistance through the IHKA to ground at the valve connector pins, with the engine running and temp set to 60F. The resistance at the control pins for both valves started 1.5MOhms and increased to 4.5Mohms fairly quickly Those seem high (ie, limiting current flow through the valve motors). so it would seem that the controller is "telling" the valves to close. But I am guessing, since I do not know what the correct values should be.Do you by chance know what the correct "full open" and "full closed resistance values should be? Thanks! Dave
