HVAC either won't turn off, or it shuts off on it's own...

[Mike-AZ]

I've been having this problem for a few years now, and it seems to exaggerate when it's very hot outside. If I have the HVAC on fan speed #1 for a while, the HVAC system will shut off on it's own and stay off until I restart the car. It will not respond at all to any inputs until then. The other thing that has been happening is that when I have the HVAC system on and I go to turn the car off, it will stay on no matter what I do. So I have to turn the system to "off" if I don't want it to drain my battery. This to me screams worn relay, but I am not certain. I have already replaced the blue cube resistor thingy under the dash near the pedals, and this has not helped. Anyone know what's up?

1994 BMW 540i
140,000+ Nikasil miles

[joshua43214]

You have a resister pack? you should have the "sword" fan resistor. This is the normal cause of the fan shutting off after it has run for a while. You say it will nto respond to any inputs, so the AC compressor will not come on? or its light? can you hear the recirc flap move whenyou hit the button? or is it just the fan that stops running?

Any chance the automatic ventilation is running? I am not sure if it will turn on before the door is opened after shut down, but it may. Look in the owners manual for details about activateing it.