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2006 chevy trailblazer_lt
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Discussion Starter #1
So I'm at a loss. My HVAC has the following list of issues:


[*]The air is blowing out of all vents. It is set on floor, and if you hit the mode button it will start clicking behind the dash. However, it still blows full out of the vent and defrost. In other words, when I don't want it coming through the vents I have to flip them closed, otherwise, it will blow out of everything at once.


[*]I have the digital controls, and when I attempt to change the temperature I have to move the knob one click at a time. Otherwise, it will jump back down to 60.


[*]The ambient temperature will not show correct. I have replaced the sensor twice and changed the control module on the dash. Both old and new have all of the aforementioned problems. It used to stay at a constant 50 however within the past month or so it has started reading in the negatives, and with it being warmer outside means I have no AC.

This is a 2006 Trailblazer LT with the 4.2 I6. Approximately 217,000 miles.
 

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2005 gmc trailblazer_ls
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157 Posts
You mentioned that you replaced the digital control module. Did you reset the HVAC?

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2006 chevy trailblazer_lt
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Discussion Starter #3
I did the three button reset multiple times, and it seems to just make the problem worse and it will reset to -3*
 

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2005 gmc trailblazer_ls
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I'm not talking about 3 button reset. I'm talking about disconnecting a battery for 30 minutes and pulling HVAC a and HVAC B fuses under the passenger rear seat.

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2006 chevy trailblazer_lt
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Discussion Starter #5
Have not done that, do the problems I have seem to be able to be fixed by doing that?
 

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2005 gmc trailblazer_ls
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Disconnecting the battery and pulling HVAC fuses resets settings in a PCM for digital controls. Worth of trying.

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2005 gmc trailblazer_ls
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Please remember after resetting and reconnecting the battery and putting a fuses back in turn the ignition key to on position without starting the vehicle and let the automatic climate control recalibrate itself. It will take about a minute to minute and a half to do that and it cannot be interrupted. I hope this will help

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2004 gmc envoy_slt
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It is not necessary to disconnect the battery and pull the HVAC fuses, that is redundant. Do one one the other. If you hear clicking that is a sign that one of the actuators has broken gears and needs replacing.
As far as the temperature readings, if you have already replaced the temp sensor and the main control unit, that would only leave the wiring. Attached is the schematic for the system.
 

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2006 chevy trailblazer_lt
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Discussion Starter #9
Did the reset with no help. Unplugged the sensor in the grill and it still shows - 33. Any other suggestions?
 

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2005 gmc trailblazer_ls
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You did all the necessary steps with the replacement and calibration of the HVAC unit. Unfortunately he leaves you all new with the wiring problem. Death can be very tricky tracing problem. Did you check the interior temperature sensor right behind the driver door? It also might sound crazy but many people complain about weird problems associated with a ignition switch. Maybe it's worth of checking that out.

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I'm sorry for my Google spelling its interior temperature sensor. It is located right after driver door right below the side airbag. It looks like a mini speaker. I have no way to get inside there's a small electric fan with the temperature sensor. That's what I heard.

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Also like I mentioned before a lot of weird electrical and control symptoms comes from intermittent or defective ignition switch

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Discussion Starter #15
Okay thanks. Should I be able to hear the fan? Would you happen to have a part number? Put a test light on the sensor by grill and showing power.
 

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As far as I know sometimes this fan especially when filled with dust will become very noisy. If you turn a climate control on on a lowest fan setting and put your ear right next to the small fan you should be able to hear it running. However if it does not work and the air it's not forced into the sensor then you will have no control of interior temperature. That's what I heard at least. Unfortunately I don't have a part number for neither of sensor or a fan.

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