billie

Quote from Phil in "AC hit or miss":

Billie,

Did your friend cut the blend door out or take everything apart? I thought that I had to have a blend door issue with the difference in temp but the blend door was fine. There is an upper blend door and the bottom follower door. Usually only the main (direct motor driven door is the problem).

If you cut out the blend door opening like you do in the heatertreater instructions you can run the ac and see the inefficiency in the evap core by touching it or with a temp gun. The way all of the ducting works on these the evaporator is cold that blows into the driver side channel and a lot warmer on the passenger side. Ait is blowing equally hard through the evap but the cold is gone towards the firewall side which is what is directed at the passenger air tunnel.

From what I have learned, everything is the same for the single and dual control except that in the dual control another motor controls that passenger doors. No sensor directs to the driver. It is just that the drivers air blows over the evaporator side that is cool and this is the air the driver gets. Once the air gets past the blend doors the passenger and driver air does not mix.

Once you cut one of these open and observe what is happening it is easy to understand what is going on. Before I saw it I thought that it had to be a blend door problem.

End Quote

The truck is a 2003 Laramie and the original brochure states that it comes standard with dual control. A serial number search suggests it had single control. There has been someone doing some creative work in the dash. It looks like the original dash may have been replaced along with some cut wires. The heater controls do not appear to have been touched and the plugs for dual and single are identical.

We took the dual control out of my Laramie and everything works as it should. The existing single control and a new replacement single do not operate the door on the passenger side (drivers side is good). Does anyone have a wiring diagram that shows how a single would control the dual doors? Or can anyone confirm that the doors are the same for single and dual control as suggested by Phil above?

He is OK with single control but his wife wants her AC

TIA

billie

On another note, during the testing, the doors really torque hard on the stops and the computer seems to learn the travel distance. If you do not move the temp lever(s) to maximum, then the doors do not reach the end and the associated torque against the stops. Point being that if you do not use the max temp settings (far right) then you may increase the longevity of the blend doors.

Cya

Phil E.

Billie,

I sent you a pm for the site to visit to better understand how this works. If you have a blend door issue on the dual control for the passenger I think that the entire dash has to come out instead of cutting into the box.

There are 2 sets of doors (top and bottom) on a dual system I belive. The easiest fix is to buy the heatertreater door and go to a single control system. This is a 2 hour job for $150 in parts if you do it yourself.

You can email the company I sent you and they will tell you the options.

Phil

billie

Thanks Phil, looks like all the answers we need.

It looks like the dash control was changed because it has the 2 servo motors as listed on the heater/treater site. Odd that the serial number search says single control when in fact the system is a dual box.

The simple solution right now is to buy the dual control dash unit since mine worked great in his. Should be installed tonight.

Cya

truckbouy2

They're all dual box (Split Plenum).... Mode Door 1 (Defrost/Floor), Mode Door 2 (Panel), Blend Door, Recirc Door....(4) Servo Motors

billie

They are all dual chamber but the dual control has an extra motor, 5 total. The 2 sets of blend doors are split to separate, driver/passenger side control.

truckbouy2

Yup......Thoust art correcteth...