Mode control and defrost issues

blwn31

Original poster
Member
Jan 26, 2012
12
Here's my issue. Got an '02 TB LS. Couldn't get the mode control door to go to any defrost mode without the dreaded clicking. It would only blow air out the floor, face or floor and face vents. Found the Mode Control Actuator had a chipped off tooth and have resolved that issue. More on this later. While I've been wrenching and learning the system I have discovered the defrost actuator is not commanding the door to move. I pulled the actuator apart and did some wiring checks and the feed back potentiometer checks out as well as the motor. I then removed the motor wires from the circuit board and ran the motor manually with jumpers and the battery. That works too. Plug it back together and plug the actuator into the TB and it won't work. Tried recalibration, no help. Now for the kicker. I took the defrost actuator and plugged it into the left heat control plug and it works as advertised. WTF? I'm guessing a computer issue? And if it's a computer issue, is it the control head? I haven't dug into my manuals yet, this site is way more informative than any manual could be. Any help appreciated.
Since I haven't been able to get the defrost actuator to operate in it's own position, I took the needed gear out and used it in the mode control actuator for a temp fix until the new actuators get here. Also, must of had a piece of debris in the door as well, as I had to use a pair of pliers to get the door to go to it's full CW rotation position. Moves smoothly now, and works as it should.

Keith
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
During recalibration, does it cycle to the endpoints? Could be wiring or the control module if it doesn't.
 

blwn31

Original poster
Member
Jan 26, 2012
12
So far I have checked wiring consisting of ignition 3 voltage circuit 341, defrost door control circuit 2274. These circuits check out good. I will get he other 3 this weekend. Off to work now.

Keith
 

mrjean

Member
Jul 15, 2012
110
blwn31 said:
Here's my issue. Got an '02 TB LS. Couldn't get the mode control door to go to any defrost mode without the dreaded clicking. It would only blow air out the floor, face or floor and face vents. Found the Mode Control Actuator had a chipped off tooth and have resolved that issue. More on this later. While I've been wrenching and learning the system I have discovered the defrost actuator is not commanding the door to move. I pulled the actuator apart and did some wiring checks and the feed back potentiometer checks out as well as the motor. I then removed the motor wires from the circuit board and ran the motor manually with jumpers and the battery. That works too. Plug it back together and plug the actuator into the TB and it won't work. Tried recalibration, no help. Now for the kicker. I took the defrost actuator and plugged it into the left heat control plug and it works as advertised. WTF? I'm guessing a computer issue? And if it's a computer issue, is it the control head? I haven't dug into my manuals yet, this site is way more informative than any manual could be. Any help appreciated.
Since I haven't been able to get the defrost actuator to operate in it's own position, I took the needed gear out and used it in the mode control actuator for a temp fix until the new actuators get here. Also, must of had a piece of debris in the door as well, as I had to use a pair of pliers to get the door to go to it's full CW rotation position. Moves smoothly now, and works as it should.

Keith

what part did you use for your 2002 defrost actuator? ive been trying to buy one however none of my auto parts know the part number for some reason. i have sorta of the same issue going on. i think the part is doorman 604-111

Front vent only-lots of air
Floor vent with front defrost- air at floor only (strong around high gas pedal, bit of air at defrost. Per paper I placed on above defrost I could tell its leaked air coming out)
Floor only-air at floor (same as above)
Floor and front vent (air on front vent only no air on floor)
Front defrost- air at floor, no air at defrost (Same as floor vent with defrost above)
Recirculate- works on anything that has front vent mode. Blinks on all others. Same results as above in regards to air flow.
 

IllogicTC

Member
Dec 30, 2013
3,452
mrjean said:
Recirculate- works on anything that has front vent mode. Blinks on all others. Same results as above in regards to air flow.

Recirculate won't work on anything that has the defrost vent active, by default. I THINK it also goes the same for floor-only, too. The light blinks as an indicator that it can't perform that function with your current selection.
 

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