dieseldoc Posted November 24, 2014 Share Posted November 24, 2014 2006 F-350 XLT with Manual climate control. It is stuck on high heat all the time unless it is set on max a/c and the water valve shuts. Followed pinpoint test L in the shop manual starting on page 412-00-76. I found in step L4 that my potentiometer tested at 60 ohms in the bottom of the range which is far less than the 150 ohms in the manual however the high side is spot on. Since the part is 20 bucks and it was out of spec I installed a new potentiometer and checked operation, no change. Started the diagnostic over with same reading on new part as old. So I kept troubleshooting as though it was in spec all things checked out. Removed the blend door actuator and the door is not stuck or binding(can move it with one finger back and forth). I went back and read through the normal operation paragraph again and tested circuits it describes, and got expected readings. I at this point assume that there is something failed in the actuator. Took the top cover off the actuator and found nothing burnt or broken inside. I tested voltage at the motor and it varies from 7.4 volts to .6 volts as the temp control is moved back and forth from hot to cold. Until now I have not had the pleasure of working on the hvac part of these vehicles and so needless to say have no experience as to what normal voltages and resistances are on these systems. My question is am I on the right track here and is the blend door actuator a "common" failure item in these vehicles? thanks for the inf guys, much appreciated. Quote Link to comment Share on other sites More sharing options...
8WA Sman Posted November 25, 2014 Share Posted November 25, 2014 Sounds to me like the motor inside the blend door actuator went bad. If the control circuit voltage to the actuator is varying and your b+ & - are good it has to be a bad actuator. Quote Link to comment Share on other sites More sharing options...
tonybullitt Posted November 25, 2014 Share Posted November 25, 2014 I would replace actuator also. I have not done them in 05-07 style truck but have done many in the 08-10. In my personal 2010 I have replaced both blend door and the mode door actuators. Quote Link to comment Share on other sites More sharing options...
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