I shut off my car today,and the blower wouldn’t shut off. I left the car off and about 30 minutes later the battery was dead and still heard and humming noise.
Will it shut off through the fan switch? With the complexity of control modules, it could just need a reset. The quickest way to do this is disconnect the negative cable from the battery, and let it sit for a few hours. Reconnect and see if the problem goes away. If not, replacing the climate control module may be the only other option. Until that is done, look through the owner’s manual, locate the fuse that protects the climate control system, and pull that fuse.
The blower speed is most likely being controlled by a solid state power module. The variable speed control systems use this kind of set up. The module is tied directly to power on one end and to the blower on the output. Another lead comes from the HVAC module to control the motor speed. Sometimes these modules can fail in a shorted condition which then ties power to the blower continuously, even with the ignition OFF. I suspect that the speed control module has failed in that very condition. The module could have failed due to excessive current draw from the blower so the blower motor current should be checked at least before installing another module. You may need to replace the blower motor also. It may be wise just to replace the motor anyways if you have spend a lot on labor just to get at these things. The cost for the module runs about $120 dollars.