So i have been dealing with this for far too long now and could really use some help on where to go next. Yes I have checked all fuses and relays and replaced all of them that I know of. Yes I have replaced the blower control module behind the glovebox. Yes I replaced the blower motor itself. And last I just got done replacing the ATC unit itself in the dash above the radio. I'm really not sure what to try next. So the fan stays on high speed no matter what. I can change between defrost/ floor/ and all that no problem. It switches between hot and cold no problem. When I power it off from the head unit it stays on high speed but with no heat or cold air just air. The only way for me to turn it off currently is to remove the relay under the hood in the fuse box and plug it back in when I need it on again which is very inconvenient. So before I go wiring a toggle switch to the relay to turn it on and off I figured I would try to ask some experts on here . Please help me figure this out as i am already $250 into throwing replacement parts at it.

 

have a volt meter? if so take the relay out car off probe pin 86 is there a ground all the time there ?

 

Just to clarify, are you referring to the control module under the glove box or the relay in the fuse box under the hood?

 

under the hood. in the glove box is called a resistor module

 

So I tried to look it up before I asked but I'm finding all different thing so would it be possible for you to explain how I go about testing it and how I would tell if it's grounded all the time. I just ordered a new multimeter that could test continuity and I'm ready to give it a go but not really sure what I'm looking for. Thank you.

 

So I tested the relay and everything tested how it should. I also threw a new one in there just to be sure and I still have the problem.

 

remove the relay look at where the relay goes and look at this pic for reference. Put black lead on Negative ground or battery ground. then put the meter on Ohms then use the positive lead and probe pin 86 in the fuse box with the key off does it show OL or does it so numbers?

 

it shows OL

 

when you pull the relay does the blower motor still stay on?

 

No. It turns off when I pull the relay