Heater Fan Runs on/off all night! - 2001 540i

[Herr Koobel]

My climate control fan seems to be pulsing on and off all night. First really cold night here (NYC area) finally killed my original battery. Fan runs regardless of what setting , ie AUTO, or any manual setting.

Any thoughts folk? Thanks in advance.

PS. My outside thermometer was damaged from dragging on the pavement. Could this effect the fan?

Pat Leber
2001 540I / 6spd / sport package
1983 Porsche 944 Club Racer.

[readyreader52]

Have you received any resolution on this? I recently acquired a 2001 530i and twice now I have found the battery dead. I had it in my garage a few days ago and then I heard a fan running. It seems to be the heater fan on very low. I opened the car door to get in and after I sat down it turned off. I exited the car and several minutes later I heard it running again for 1 or two minutes. This happened three times while I was in there. The next morning I started the car and drove it two miles to work. 9 hours later I tried to start it to go home and it would not turn over. Lights very dim. What can cause this fan to run when car is off and no key in ignition. Or could this be the little fan in the bottom of the computer box that I am hearing? What controls this fan

[xsperf]

it may be your aux fan trying to cool the radiator, was your engine overheating? yea its probably a temp sensor(not the outside one)

[c1apton]

I agree w/Xsperf, sounds like your aux fan is running the battery down. I'd check the actual connection at the relay/sensor - a loose or coroded connection would cause it to run erratic.

[gemnilvr]

this is the final stage unit also called the blower motor unit! they are sold on ebay for about $75 and is an easy diy project! this will fix the problem and is very common!!

[MaicoOens]

thanks for sharing a very useful information. this will help each and every member of the site.