2003 escalade A/C controls and Blend door actuators

[izzy_Britton]

Backstory: I bought a 2003 Escalade that had a bit of a dashboard fire/melt down. fire fights tore the dash out in pieces. I have replaced the main dash and components. The replacement dash came from a wrecking yard and had many wires cut because of the lazy people cutting wires to remove components.


so here we are today. I have resoldered all the wires and connectors in place that run the speedo radio, and the automagic a/c controller.

The a/c only blows HOT air. I do realize that the system may be out of freon or whatever, but i am thinking that the issue is actually the blend door actuators. what i have going on is that the bottom actuator that is in the center of the dash near the floor does not appear to be working. I have replaced the actuator but is it still not cycling.

does anyone know the ins and outs of this actuator and what it actual does and what function needs to be performed on the control panel to make this bottom actuator cycle? I have now disconnected the actuator from the a/c box so it is hanging free but wires are plugged in.

I can manually force the actuator to one position and turn the truck key on and it will default to what i assume is the 'closed' position. there is nothing that i am able to change on the dash controller to make it 'open'.

what causes this actuator/door to change position?

anybody? i can guess that i got a wire crossed but i do not have a diagram to confirm the wire plug in on the back of the dash controller has 2 sets of identical wires (colors and gauge) blue and brown. identical.

thoughts?

thanks in advance,

-Izzy

[hatzie]

The HVAC controller can loose its' marbles when you power it up without all of its' sensors and actuators connected.

Reset the HVAC actuator calibration as follows.

1. With the engine off pull the 10A HVAC/ECAS fuse in the engine bay fuse panel and leave it out for a minimum of a full 60 seconds. Alternatively you could disconnect the battery negative cable for 60 seconds but it will clear the emissions readiness flags and may set spurious fault codes in various modules.
2. Re-install the fuse and start the truck.
3. The HVAC should default to 74° if it's memory has been cleared.
4. DO NOT TOUCH THE HVAC CONTROLS.
5. Let her run for at least 120 seconds... 2 full minutes. The HVAC controller will excercise the actuator motors to find the limits.
6. Turn the ignition off for at least 10 seconds and no more than 30 seconds. 20 seconds is a good in-between.
7. Re-start the engine and test the controls.

If you have a failed ambient air temp sensor or a failed cab temp sensor or either is disconnected it still may not like you.
The ambient air temp sensor should be clipped to the sheet-metal behind the grill. On the LH side IIRC.
The cab temp sensor is behind the tiny grille, that looks like it should be a microphone, in the headliner over the drivers' head.

[homemade87]

I have now disconnected the actuator from the a/c box so it is hanging free but wires are plugged in.




Never power up an actuator when not fully installed . It wants to go beyond the limits of what its operating range . If you determine this to be the case this video may help .


https://www.youtube.com/watch?v=vWBGKfl7k24

[hatzie]

If you leave the actuator hanging, without being bolted or latched down and connected to the linkage etc inside the HVAC box, the HVAC controller will still be angry with you because it can't calibrate the stop locations.

Why?

The actuators don't have stops because it's less difficult to assemble and service if you don't have to line up timing marks and the engineers figured someone would mis-assemble them and break parts... out of stupidity, malice, or haste. A for engineering effort. They made em easy to assemble and easy to service... but people can still screw them up. Nothing is foolproof. Fools are too ingenious.

What the procedure I outlined in my last post does is cause the HVAC controller to run a calibration cycle.

Here's what it's doing... The HVAC controller cycles the actuators several times from stop to stop. This calibrates software stops based on the current draw on the tiny little DC motor in each of the actuators. Once the running current is known, between the linkage travel stops, the HVAC controller can accurately determine when the linkages the actuators are attached to have reached the end of their travel by the rise in current above the "normal" current needed to run the linkages.

If the linkages or doors bind up the HVAC controller will think they have reached the travel limit and stop. The small DC motors are completely capable of breaking the linkages and stripping the internal gears in the actuators. The controller limits the torque applied in an attempt to avoid that.

Boy that was wordy. Hopefully it's clear what's happening.

BTW: GM used this same scheme in many vehicles. The last generation of W-Body Impalas are notorious for the HVAC actuators stripping gears as they age and get brittle.