HVAC blower motor only blows on high, even in the off position. Replaced.....


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Dec 16, 2014
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Hello friends. I know this is a common topic and I have done a lot of forum searching on it but my situation is different from anything I have found.

I have a 97 Mark VIII and the fan blower blows on high irregardless of where the blower speed thumb wheel is set. When you push the off button the fan speed increase even higher and the display shuts off as it should. So I thought it was a bad blower control module. I replaced it with a used one. Now with the used one the blower does not blow at all. So I thought the used one must be bad but in a different way. So I bought a new one. Still the blower does not blow at all. All of the functions on the EATC work properly. I can hear all of my blend doors opening and closing and air blows out where it should with the old blower control module.

Next I did the EATC self test. I got code 155 which is a "false code." I only get the code 155 with the key in the run position and the car off. If I clear the codes and do it with the car running I don't get a code. I get the same results with the old blower control module plugged in or the new one.

My A/C does work with the old blower control module. I am not sure that my heat works but that shouldn't affect the blower not working.

The replacement blower control modules have the same part number and are not out of GEN 1 car, those are physically larger.

Does anyone have any ideas? I am completely stumped. Thanks -Joe
I would try swapping EATC at this point as it seems you've done all other things I would suggest trying first.
Very strange it does not blow at all with a new control module, maybe all of the ones you've tried (including the 'new' one) are duds?
I had the exact same symptoms not long ago on a 97 I sold to a guy. I replaced the control module and same thing as yours, no blower at all. So I replaced eatc, and also plugged in original control module, same symptoms as original. So in other words I had to change eatc and control module. Not sure if control module damaged eatc, but that's what I'm assuming.
Thanks Necrosan and chargerxr, I agree I am leaning towards it is a bad EATC. They are cheap enough on ebay and if that doesn't solve my problem I can always sell it back out. I will let you know what happens.
I did swap out the EATC and now everything is working again! Thanks everyone!

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