HVAC issues, blend/panel actuators don't work.

[jfranco]

So I've been trouble shooting this HVAC issue on a family member's 2002 yukon. Its got the rear HVAC controls, and the "computer controlled" controls upfront. (IE: no resistor module).

The issues started when the blower motor completely died. It didnt do anything funny, just stopped working one day. First thing I replaced was the blower control module (The resistor pack equivalent for the computer controlled climate models?) That made the fan spin, but I couldn't get the actuators for the temperature/panel selectors to do anything; No matter how I turned the knobs, it still blew out of the panels and heat only.

I ended up finding the blend actuator itself, i pulled it out and just spun the blend door by hand. This made the AC blow ice cold, and the heat blow nice and hot depending on how I turned the flapper. But no matter what I do, the damn thing is still stuck on panel, i can't get it to blow from the defroster or the floor vents.

I replaced the fan switches, and this changed nothing. I'm completely at a loss for what to do next. I tested the motor for the blend actuator and it spun fine when hooked directly to a battery supply. Any idea what would make both the blend actuator and the panel actuator not work simultaneously?

Thanks for the help.

 

[chip]

The control unit?

 

[jfranco]

I'm not sure exactly what the control unit is. Can you clarify a bit?

 

[chip]

The digital control unit that you use to change the temperature in the truck. The actual "climate controller".

Make sense?

 

[jfranco]

Ah, yes. Thats what i refered to as the "fan switches" (that's what autozone lists the part as, anyway), and I already tried replacing it. The new one made no difference to the old one.

 

[chip]

Damn!

 

[afpj]

If you disconnected the battery changing out those parts, you may have to recalibrate the actuators. There is a write up somewhere about that but I'm having a senior moment and can't remember the title.

 

[jfranco]

Now that you mention it, the battery did die at some point during the install process. I know exactly the post you're talking about and will search for it and give it a whirl tonight. Thanks.

 

[jfranco]

I tried every combination, and every sequence of key on/ignition on/fuse pulling i could find and nothing made a difference. I'm getting voltage to the blend actuator, but the actuator motor isn't moving at all. I have no idea what the voltages are supposed to be, but I was getting differing voltages depending on which wires I hit with the voltmeter. None of the voltages changed when the knobs were turned either.

I went and bought a new blend actuator from Advance Auto and the same issue is still there. Theres zero movement from the blend actuator. I'm completely at a loss for what to do next.

So just to recap the issues:

Blend actuator is not functioning at all
A/C or heat, depending on how I manually spin the blend door itself, is blowing out of the panel
Heat is blowing from passenger side on the floor, regardless of blend door position
Can't adjust heat/ac with the knobs
Can't adjust panel/footer/defroster with the knobs.

Replaced the entire control switch/knob unit. No change
Replaced the blend actuator. No change
Replaced the control module.

HELP!

 

[chip]

I'm thinking check grounds.