2004 rear fan

[Gnarley]

I'm new here and have a 2004 Yukon SLE w/130,000 miles. Barely any problems until now. I have Auto climate controls front\rear.

The rear A\C has the fan blowing on high with the engine running and I'm unable to adjust it. It does not operate with the engine off. I suspect it's the Blower Motor Resistor.

Can anyone validate my diagnosis and perhaps suggest the replacement part number? I found a Standard Ignition RU-807 Blower Motor Resistor for $219.00! That seems a bit high and believe there is an alternative for much less.

Thanks

 

[Scottydoggs]

do you have controls on the back of the console, if so maybe its set up to be in control. try changing the fan speed from back there if you have em.

 

[Rocket Man]

What he said, but maybe overhead controls for the rear so the 2nd row passengers can adjust it. That’s what mine has.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics, please.

Generally, when the blower speed resistor fails, one or more fan speeds no longer work, but I've never hear of not being able to shut the fan completely off, due to a fan blower resistor failure. Other folks more familiar with the 2004 model year will chime in

 

[Gnarley]

 

[Gnarley]

The front actuator seems to work fine, however, the rear actuator seems to go to the A/C side no matter what. I removed the cover to see if I could trick it to resetting and it seems no matter what it opens the door to the A/C.

Thoughts?

 

[Rocket Man]

View attachment 267762 View attachment 267764 View attachment 267765 View attachment 267766 View attachment 267767

If you set all 3 controls to no fan speed it still blows on high? Did you try the reset process? Try this:
https://www.tahoeyukonforum.com/threads/recalibrating-hvac.81057/

 

[Fless]

^^^ THIS. Or if you have access to a Tech 2 it can do the reset.

 

[Gnarley]

If you set all 3 controls to no fan speed it still blows on high? Did you try the reset process? Try this:
https://www.tahoeyukonforum.com/threads/recalibrating-hvac.81057/

Actually no, it has now stopped blowing and operates as it should! I did nothing other than come out the next day and started it and the rear did not run. Then after a while, the fan came on and the blower was running and seemed to be trying to run as if on Auto, it wasn't high or off, it was like it was hunting for a speed to blow for maybe 3-5 minutes and then stopped. Then, for an hour or so as I worked on the Temp actuator I had full manual control from the front or read fan speed. It seems really strange?

 

[Rocket Man]

Actually no, it has now stopped blowing and operates as it should! I did nothing other than come out the next day and started it and the rear did not run. Then after a while, the fan came on and the blower was running and seemed to be trying to run as if on Auto, it wasn't high or off, it was like it was hunting for a speed to blow for maybe 3-5 minutes and then stopped. Then, for an hour or so as I worked on the Temp actuator I had full manual control from the front or read fan speed. It seems really strange?

Sounds like it did a calibration itself. That’s great.

 

[Gnarley]

Sounds like it did a calibration itself. That’s great.

Yeah, except it only wants to blow cold from the rear, if I leave the rear blend actuator connected. I set the flap to heat and reset the gears to stay on heat and closed it up and did not plug the connector as I determined it will not stay on the heat if plugged in, so what would cause that?

Thanks

 

[Rocket Man]

Yeah, except it only wants to blow cold from the rear, if I leave the rear blend actuator connected. I set the flap to heat and reset the gears to stay on heat and closed it up and did not plug the connector as I determined it will not stay on the heat if plugged in, so what would cause that?

Thanks

Try the calibration that I linked to in the tech section.

 

[Doubeleive]

View attachment 267762 View attachment 267764 View attachment 267765 View attachment 267766 View attachment 267767

Just write down the part number on that rear blower resistor and take it to the auto parts store or order it online and/or take the old resistor with you to match it up at the autoparts store
99.99999% chance it is just the resistor gone bad, no sense in complicating it.

 

[Doubeleive]

Yeah, except it only wants to blow cold from the rear, if I leave the rear blend actuator connected. I set the flap to heat and reset the gears to stay on heat and closed it up and did not plug the connector as I determined it will not stay on the heat if plugged in, so what would cause that?

Thanks

watch the actuator gear on the actuator that is closest to the blower motor, when you adjust hot to cold or vica-versa you should see it rotate, if it does not rotate then replace it.
as you turn the heat adjust you should see the actuator move usually about 1/4 turn if set to a middle temp and it should stay there unless you adjust the temp more, if it rotates fine and appears to be adjusting on it's own (like to cold when you have it set to hot) then you may have a bad ambient air sensor in the headliner.

 

[Gnarley]

I followed the instructions below. Same results, the rear blend door moves to cold and will not adjust. Thoughts?

1. Start the engine and turn all the controls to the off position, (rear controls too if they're acting up), temp turned all the way down.

2. Shut off the engine.

3. Remove the positive battery terminal and leave it off for 10 minutes.

4. When it's time to reconnect it, touch it to the negative battery terminal to make sure any residual electricity is discharged.

5. Start the engine and DO NOT TOUCH THE HVAC CONTROLS FOR 5-10 MINUTES!

 

[Rocket Man]

I followed the instructions below. Same results, the rear blend door moves to cold and will not adjust. Thoughts?

1. Start the engine and turn all the controls to the off position, (rear controls too if they're acting up), temp turned all the way down.

2. Shut off the engine.

3. Remove the positive battery terminal and leave it off for 10 minutes.

4. When it's time to reconnect it, touch it to the negative battery terminal to make sure any residual electricity is discharged.

5. Start the engine and DO NOT TOUCH THE HVAC CONTROLS FOR 5-10 MINUTES!

Could have a bad ambient air temp sensor like Wes said or the actuator might be bad.

 

[Gnarley]

I previously swapped the actuators and when the blend actuator that controls the hot and cold was moved into the outlet control in the front it operated as expected and the one from the front now in the rear position controlling the blend door went right to the cold position.

By substitution both actuators are working as expected and correct. So an ambient temp sensor could do that, what about the control module or whatever the component is that tells the actuator what to do?

 

[Rocket Man]

I previously swapped the actuators and when the blend actuator that controls the hot and cold was moved into the outlet control in the front it operated as expected and the one from the front now in the rear position controlling the blend door went right to the cold position.

By substitution both actuators are working as expected and correct. So an ambient temp sensor could do that, what about the control module or whatever the component is that tells the actuator what to do?

It’s controlled from one of 2 different control heads either from the back of the console if the front one is set to Aux or from the front one if it’s not. If it’s doing the same thing no matter which control head it’s being run from then that answers your question.

 

[Gnarley]

It’s controlled from one of 2 different control heads either from the back of the console if the front one is set to Aux or from the front one if it’s not. If it’s doing the same thing no matter which control head it’s being run from then that answers your question.

It didn't answer my question, I don't know what I should consider replacing

 

[Rocket Man]

It didn't answer my question, I don't know what I should consider replacing

I doubt both your control heads are telling that actuator to do the exact same wrong thing so I would try replacing the rear ambient temp sensor. You have to partially pull the headliner down to get to the back side of it. It looks like a small fan a couple inches in diameter.
https://www.rockauto.com/en/catalog...nditioning,cabin+air+temperature+sensor,14376