2008 Mustang GT defroster not working

[Lehotsky1]

Need of some help. 2008 mustang gt, a month ago was making knocking sound from dash. Replaced the actuator making the knock and it stopped. However, now my main defroster setting for the windshield is not operating; only blows air through the foot vents. Any advice or tips would be greatly appreciated.

 

[Dino Dino Bambino]

Sounds like another actuator has broken down. Which one did you replace?

 

[Lehotsky1]

Not sure exactly what actions the one I replaced controls, however I essentially had to take the glove compartment out to get to it; there are two actuators once you take the glove box out and I replaced the one located higher up behind the dash.

 

[Lehotsky1]

Pretty sure the one I replaced had something to do with the modes; knocking noise became an issue when I would turn on any function essentially. Just strange because my defroster worked before I replaced the actuator.

 

[Dino Dino Bambino]

Remove the lower actuator and bench test it. Attach one test wire with crocodile clip to the pin at one end and a second test wire to the pin at the other end of the wiring connector socket. Touch the other end of first test wire onto the positive terminal of a 12v car battery, and the other end of the second test wire to the negative battery terminal. You should see the gear mechanism of the actuator turn slowly if it's working properly.

 

[datmbn]

I think the accurator behind the instrument cluster is the one not working or you can have missed the controllarm when you monted the acurator

 

[datmbn]

If there are problems with heat/air flow, chances are it's because one of the accurators sitting on the heater is broken.

It is 4 x accurators, which 3 are equal and one dissenting.

It is 1 behind instrument clustr, as I understand regulates the air between the floor and the windshield. Since it sits two servo on the right side of
heat pack, reachable behind the glove box, the bottom one handles regulation between cold and warm, and the upper regulating air between central air and
floor / defrost. These three accurators are equally fashiond, and keeps track of where in the regulation they are, using some kind of potentiometer,
conekted with the rotation.

then there is a accurator close to the fan motor, which handles switching between fresh air / recirculation, this accurator has no potentiometer,
so there must be some other way to know when the two positions are reached (do not how).

The 3 accurators sitting on the heat pack can be exchanged/replaced with each other without problems, just make sure the accurators are
adjusted to the zero position (arrow mark on the back). it is possible to put one of these also in the fourth place (but not vice versa)

The symptoms that some accurator is bad, is difficult to regulate air flow or heat, and that you usually hear a popping or grinding
sound behind the instrument panel when adjusting the heat.

Fortunately, these accurators are neither particularly expensive or difficult to change, but how do you know which accurators is broken?

A little rough, I think it is like this:

1. You can not adjust the hot/cold = lower accurator behind the glovebox
2. no central air or can not turn off the central air = upper accurator behind the glove box
3. no heating or no defrost = accurator behind the instrument cluster
4. no recirculation or no outdoor air = accurators at the fan motor

 

[Lehotsky1]

One item that was different between the actuator I swapped and the one I replaced was the positioning of the control arm. Think I will start there. Thank you all for the responses. Much appreciated.

 

[MrBhp]

One item that was different between the actuator I swapped and the one I replaced was the positioning of the control arm. Think I will start there. Thank you all for the responses. Much appreciated.

Yep. The control is expecting it to be at a certain spot, it's not there. At least that's how a few I have worked on are.

 

[LaserMan]

I just replaced the actuator on the driver's side, behind the speedometer (it is a challenge to get in there!). In the process, I was able to gather the part numbers and functions below.

Can you switch between floor and dash? If so, it seems that the problem is still with the actuator you replaced (dash/defrost). Are you confident that you were able to insert the tip of the new control arm into the slot on the actual vent arm when you replaced the first actuator? It's tricky...

Defrost Mode Door (passenger side, upper stack) - dash/defrost control
Fort Part# YH1870 (Dorman part 604-233)

HVAC Mode Door (driver side, upper stack) - dash/floor control
Fort Part# YH1870 (Dorman part 604-233)

Temperature Blend Door (passenger side, lower stack) - hot/cold temp control
Fort Part# YH1865 (Dorman part 604-231)

HVAC Door Actuator (passenger side, by feet) - outside/recirc air control
Ford Part# YH1869 (Dorman part 604-232)