I have done a search but haven't been able to find a post about my exact problem.
Here in the winter it takes a long time to get any amount of heat out of the diesel, so I usually run the auto-climate control at max temp(30deg C here in Canada) with the selector set to split between the feet and defrost. When the truck finally starts blowing heat, it takes 20-30 miles, I back off the temp setting to 22. However, the truck doesn't stop blowing full blast hot. So I keep backing off on the temp until I get to the minimum setting of 15deg. It then switches to no heat at all, then I tick it up just one degree to 16, it switches to full blast hot again.
So while driving, if I get hot, I turn it to 15 until I get cold, then to 16 until I get hot...repeat as necessary.
So thats all I have, full blast hot or no heat at all, controllable by changing the temperature one degree.
Could it be the temperature sensor in the headliner? I heard it making noise so I gave it a spray of WD40.

Don't know if this would apply to the automatic, but on a Colorado I had there was some kind of relay or transistor or something, but I had two options none or full blast when it came to the fan. What ever the part is, it reduces the power to the fan. I've seen this happen to two different vehicles with the manual option.

Try taking if off auto, and adjust the fans manually to reproduce your problem, if it does the same thing, then it is that part. I have no idea what it is called, but I am sure the dealer would know, or someone from here will know.

[quote=Slapshot;3154251]I have done a search but haven't been able to find a post about my exact problem.
Here in the winter it takes a long time to get any amount of heat out of the diesel, so I usually run the auto-climate control at max temp(30deg C here in Canada) with the selector set to split between the feet and defrost. When the truck finally starts blowing heat, it takes 20-30 miles, I back off the temp setting to 22. However, the truck doesn't stop blowing full blast hot. So I keep backing off on the temp until I get to the minimum setting of 15deg. It then switches to no heat at all, then I tick it up just one degree to 16, it switches to full blast hot again.
So while driving, if I get hot, I turn it to 15 until I get cold, then to 16 until I get hot...repeat as necessary.
So thats all I have, full blast hot or no heat at all, controllable by changing the temperature one degree.
Could it be the temperature sensor in the headliner? I heard it making noise so I gave it a spray of WD40.[/quote

Sounds to me it could be the controls itself because it should change resistance while turning the knob or buttons whichever you have, and therefore accuating the the doors in your heater box open or closed, i'm not sure on the sensor in the headliner!

I never have mine on auto. Seems like its all screwy like yours.

Air sampler ?

Air sampler ?
thats what im thinking the sensor is getting messed up readings its that or the hvac head or a temp sensor in the duct

no resistor on the digital climate control by the way

I am still thinking it is in the fan control. I have the auto climate, and if you keep turing up the temp high enough, the fan goes to full blast.

Since he had two options on the fan, high or none, that would be my first guess. The fan control is just automatic using the climate controls, but if you turn the fan up and down manually and it ionly goes off or on, that would confirm my idea.

Otherwise, it is something else.

The fan control on automatic works as it should. It is the air temperature part of it that blows 100% hot until you turn it to the lowest temperature setting.
I am going to buy a new temperature sampler, it shouldnt be too bad.

Wouldnt something to do with the bubble on the dash as that not only works for lights but also auto climate? Dont have it so Im just throwing it out there.

Hey slapshot,

Did the new temperature sampler fix it? I'm having the same problem with my 04.

Thanks

Sounds like the fan resister unit-- located behind the glovebox. You have to remove the under dash big cover to access the unit.

Is that something that will show up on the dealership scan tool?

I just replaced my resistor and my fan still dont work i guess its the blower motor now.But my shopo is full and am working on it outside so i may wait til tommorrow to try to hotwire the fan to see if it is the problem and test the wires with a test light. My ls lights are out on hot cold climate control too could it be i need that too

Well mine turned out to be an easy fix. The harness that runs to the headliner was unplugged. I don't know why anyone would have done that but at least I found it.

I havent done anything with it yet. I do know that if I leave it on full auto setting, as the interior warms up, the fan speed comes down off of full blast. This tells me the temperature sampler is working somewhat.
It could the baffle underneath that splits the cold/warm air.

I had the fan resistor changed last fall. It quit completely on me. It works as it should now.

I've run into some issues before with the heater controls and in the past simply disconnecting and reconnecting everything solved the issues. The dash bezel pulls off easily and then there are 2 7mm screws that are in the climate control panel. Remove them and they manuver the panel out by pressing on the 4 tabs (i usually do 1 side at a time). Just disconnect the wires. Count to 10 for good luck and then reconnect. Turn the truck on to test and make sure everything is fine and they put everything back.

Its odd, i've had the heater controls malfunction, my heated seats, and window controls, etc. I usually try to re-connect everything and its worked well for me.


Hope that helps,
-- D.D.

Well mine turned out to be an easy fix. The harness that runs to the headliner was unplugged. I don't know why anyone would have done that but at least I found it.

where was the harness plug located at ?

There is a panel just to the right of the E brake pedal on the firewall. There is a plastic cover over it. Remove the cover and the plug on my 04 was the top right. Hope this helps.

Test

I have to resurrect this thread.

The new air sampler did not fix my problem. I think it is the temperature control actuator. I do not hear the clicking in the vents that some hear when the actuators are hunting. I have a reason to believe a foreign object may have fallen down the defrost vents in the past (Ruger 10-22's eject up and right when shooting gophers out the drivers window). Where would one look to check for debris?

My question is where is the temperature control actuator and how can I get a look at it and tell if it is working?

I think I have the same problem. My drivers side vents won't blow hot air (passenger side blows hot).
Maybe there is a 30-06 case lodged in there somewhere :)