01 Tahoe with computer climate control. defroster only blows cool air and when u switch it from recirculate to fresh air the light blinks then goes out. ( wont let u select fresh air to run the defrost) heater works just fine from head to feet. is this an issue with that computer climate controller and can I just change that with a regular climate controller being that it has a rear heater

 

You cannot select air mode in Defog mode (not defrost), it's automatically picked depending on cabin temp and outside temp for most efficient removal of condensation. If it's only blowing cool air in Defog mode and you have the temperature control on max heat, then the most likely reason is the heater core is clogged and not producing enough heat to overcome AC. AC is forced on in Defog mode unless it's freezing outside.

If it's below 32 degrees and you're getting AC activation when you turn on defog, then your outside temperature sensor has failed (not the one for the mirror, the one for the HVAC). It's located under the passenger side daytime running lamp.

No, you cannot just swap the controllers. You'd have to swap most of the electrical harness, blower motor and blower controller.

Have you replaced the HVAC air filter yet?

 

no I have not replaced the filter, ill try that first, the heat works just fine if u don't have it in defog mode so I ruled out the heater core. if the filter change doesn't get it ill try the temp sensor getter thanks for the clarity and the tips. now I remember why I own mostly old stuff

 

Sorry to butt into this thread...


Suberbazine- I have an 02 base model (no dual climate, doesn't even have a filter that I have found like my '01). Anyway, every time you start the truck the A/C comes on. Regardless of temperature, heat setting etc. Any idea on what that is??


Thanks for any comment

 

Is this a full manual control truck with sliders, the electronic version with ***** or the Auto A/C version with ***** (Dual wasn't until 03)? The filter was a standard option with both the electronic versions of the controls, mounted in the case between the blower and evaporator.

 

It is an electronic one. Not sure on the auto AC. Here is a pic.

 

That one is sensorless and not computerized. It will start AC on every time, requiring you to disable the AC until the next ignition cycle.

 

Wow, that it weird.

btw.....how did you tell? The one in my '01 Silverado looks almost identical but it doesn't start A/C every time.

Also, can I replace it with one like the control on my '01, or is there more to it that that?

 

If the system is off the ac shouldnt come on, if the ac button isnt on the compressor shouldnt kick on. That is a simple old style system that is either shorted somewhere or has a faulty ac switch in the control head, i have seen the clutches short themselves out and come on constantly......

 

The temperature **** is a blend **** instead of a temperature specific positioning and the blower **** is a fixed step speed (resistor-based instead of PWM).

The BCM controls the AC Relay state, the button just tells the BCM to disengage the AC relay. The PCM has an AC relay override (can force relay off).

The AC light should not come on if the fan is switched off, though. If it does, you most likely have a defective control head.