HVAC mode door actuator

[westman]

I recently purchased a used 99 Yukon. Got it home and realized the air through the vents is not changing. I purchased a new actuator (one close by the gas pedal) and it's still not working. The blend door is working just fine, I can move it by hand. However, the actuator only moves a tiny bit. I pulled the wiring diagram off the net and from what I can see it should have 5 wires going to it. Mine only has three. Can some tell me or take a picture of theirs so I may compare?

 

[rayninglead]

Is it only coming out of vents and no where else? Your actuator has 2 linkages make sure they are both connected.

 

[SunlitComet]

There are no 5 wire door actuators.

 

[2door2wheel]

i had this exact same problem in my 99 hoe. it turned out to be the dash controls believe it or not

 

[SunlitComet]

For the mode door probe the white wire on the motor connector and check for a smooth volt swing as you turn the knob.

 

[westman]

I'll probe the white wire tomorrow, I'm thinking 2door2wheel is on to something with the dash controls. The more I explore common troubles, the more I learn the HVAC controls are prone to failure.

 

[SunlitComet]

Anything is prone to failure. Especially rheostats. "Scratchy" sound control ring a bell.

 

[westman]

Well, after months of procrastinating I finally fixed the problem. The head unit was bad. Replaced it with an ACdelco and everything works!