I have an 06' Silverado, the a/c, heater fan motor absolutely will not shut off unless I pull the fuse. It will run even without the key in the ignition. The only way to keep from running the battery dead is the pull the fuse under the hood. (40 amp). I tried swapping the fuse but it did not stop the fan motor. As soon as I plug the fuse in the fan motor starts running. Please help.

 

Welcome to the forum. If I'm getting this right, the blower motor runs at full speed with the 40A blower fuse in, even with key off. The switch setting on the HVAC control module probably has no effect either. About the only way it can happen is if the blower motor relay is stuck on the 40A blower fused source. This relay is part of the blower motor resistor assembly which isn't too bad to replace on the Silverado.

 

I concur, the relay welding itself on is common...replacing the relay will most likely resolve the issue...

 

Thanks to both of you for responding so quickly. EinST you have it correct. Today I will visit my friend at the local salvage yard to find replacement relay. Hopefully this will not cost me much. I will post the result of the change as I am sure I am not the first to have this problem nor the last to seek help to fix it.