A/C fan stuck on high and unable to turn off

M

mmm

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los angeles
2003 V6 LS

Has anyone ever had this issue:

When I turn my A/C on it will blow cold air but only blows at a high (max) fan speed. Pressing the fan speed up or down on my Temp Controller (DEATC is the formal name in the manual) does not adjust the flow of air. The temp controller indicates a change in fan speed on the display, but the air flow coming from vents remains at max.

Also, once I turn the A/C on using the Temp Controller I can't turn it off.
If I press the "OFF" button on the Temp Controller, all the vents electronically close (as they should) but the fan which blows the air through the vents does not turn off. So I have the equivalent of running the A/C at max fan speed, but having all the vents closed. Loud.

The only way to turn off the air attempting to come thru the vents is to turn off the car completely. The fan continues to blow max air for about 30seconds after ignition if off and then turns off. It will remain off even if I start the car again, as long as I do not turn on the A/C with the Temp Controller.

notes: 1) I can control the temperature of the air coming out by using the Temp Controller and it seems to slightly adjust fan speed as if it were running in "Auto" mode. So if its 75 degrees outside and I set it to 75 it will blow less than max.
2) All other controls on Temp Controller seem to work just fine.
3) I tried disconnecting the battery and reconnecting to see if a reset of Temp Controller was needed, but it did not help.

Is there a specific relay under the hood or in the trunk that could stick and cause only one fan speed??

Thanks in advance for any help. :)
 
No, there's no relay. You have three possibilities, one likely and two not.

1. It could be the DATC.
2. It could be the wiring between the DATC and the blower speed controller.
3. It's probably the blower speed controller.


Unfortunately, it's really hard to replace the speed controller. By the book, the dash has to come out, the refrigerant recovered, and the coolant drained. There are some hacks to work around most of that. I think they've even been posted on this site before.

Anyway, troubleshooting for this problem.
http://deneau.info/ls/s6x~us~en~file=s6xc0003.htm~gen~ref.htm#PS2-O


BTW, I'd replace the blower motor when I replaced the speed controller. The controllers usually fail due to some fault with the blower motor.
 
joegr said:
No, there's no relay. You have three possibilities, one likely and two not.

1. It could be the DATC.
2. It could be the wiring between the DATC and the blower speed controller.
3. It's probably the blower speed controller.


Unfortunately, it's really hard to replace the speed controller. By the book, the dash has to come out, the refrigerant recovered, and the coolant drained. There are some hacks to work around most of that. I think they've even been posted on this site before.

Anyway, troubleshooting for this problem.
http://deneau.info/ls/s6x~us~en~file=s6xc0003.htm~gen~ref.htm#PS2-O


BTW, I'd replace the blower motor when I replaced the speed controller. The controllers usually fail due to some fault with the blower motor.
Click to expand...

Thanks for the detailed info and the link....This will definitely be helpful....
 
I pulled a speed controller from a junkyard car, and it was horrible. Ended up busting up several parts of the air plenum to get to it. If you take your time, you *may* be able to work it out without removing the dash, but no promises.
It's located in the passenger footwell, to the left of the fan. Two large wires and three (?) small wires coming out of it. The part you can see is about the size of a deck of cards. There's a large heat sink in the plenum, which is what makes removing it quite difficult.
 
If you have access to a junkyard, you can just swap in a DATC and see if that fixes it. Yes, it's just throwing parts at it, but you can get it pretty cheap and it's a *much* easier replacement than the controller.
It may be possible to just remove the PCB from a DATC and carry it out in a pocket. :shifty:
 
oddball said:
I pulled a speed controller from a junkyard car, and it was horrible. Ended up busting up several parts of the air plenum to get to it. If you take your time, you *may* be able to work it out without removing the dash, but no promises.
It's located in the passenger footwell, to the left of the fan. Two large wires and three (?) small wires coming out of it. The part you can see is about the size of a deck of cards. There's a large heat sink in the plenum, which is what makes removing it quite difficult.
Click to expand...

Thanks for the additional info. I was kind of thinking that a junkyard might be a good spot to find one, being that they are so hard to remove.

I still have to get around to troubleshooting (electrically) to determine if that is the exact problem.

More than likely I will probably just replace both the blower motor and controller to be safe (like Joegr suggested).

I'm leaning towards just disconnecting the harness and piggybacking a new controller with a cooling fan somewhere under the dash, rather than attempting to remove the "bad" one.

I'll update when I get a chance to troubleshoot.

Thanks for all the helpful replies.
 
RockAuto has 'em new, something slightly less than $100.

It's a quite large heatsink and a large FET, so may be quite a bit of heat.

Bug me in a few weeks - I'm planning on using one for a fan controller for my Cutlass, so I should have a good idea on how much heat it generates with various loads. Haven't started that part of the work, but looks like I'll get back to the electrical work pretty soon.
 
oddball said:
RockAuto has 'em new, something slightly less than $100.

It's a quite large heatsink and a large FET, so may be quite a bit of heat.

Bug me in a few weeks - I'm planning on using one for a fan controller for my Cutlass, so I should have a good idea on how much heat it generates with various loads. Haven't started that part of the work, but looks like I'll get back to the electrical work pretty soon.
Click to expand...

Ok, cool....That would definitely be helpful to know the heat output. That way I can see if i could even get a cooling fan that would fit its size and produce enough RPM's to cool it...

I'll keep this updated once I actually get the time to get under the dash.
(I have to do my rear brakes this weekend.)

Thanks again for the help.
 
I know this is a old thread, but I just started to have the same symptoms with my blower fan and would be interested in how and or if the problem was solved.
Thanks
 
bump if anyone knows more about this one, I'm having the exact same issue.
Could be related to remote start wiring issue.
 
stumpy said:
bump if anyone knows more about this one, I'm having the exact same issue.
Could be related to remote start wiring issue.
Click to expand...

highly unlikely, it would have to be wired extremely incorrectly, as in some thing wired to things nowhere near where the wires should run...

remote starts do not run any wires to the HVAC system itself (with the one exception of optionally having the RS system turn the rear window defroster on)

its pretty much a small computer hot wiring the ignition of the car. the only wires should be ran to the ignition and PATS harness(yours interfaces with the PATS differently) at the cylinder, a wire or three into the drivers door for alarm disarming and lock control, one to the trunk switch (optional) and then one or two wires under the hood for hood pin and maybe tach.



you can easily rule this out by taking ten minutes and pulling your radio/DATC out and seeing if any wires were ran over to the DATC.


EDIT: also one wire (and maybe a relay) over to the headlight switch for parking light control.
 
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