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Hangman731

2005 Trailblazer EXT Problem

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All,

 

New to this forum and new to Chevrolet vehicles. I just recently purchased a 2005 Trailblazer EXT 3 months ago. Just recently took the vehicle into the dealer for the only problem I have had so far. The problem is with the rear heat/AC. Whenever I try to use the rear heat is never gets warm or hot enough, the dealer said it is a known problem without a solution yet and there is a case open with the engineers. The front heat works great. My question is does this sound reasonable and has anyone else experienced a similar problem?

 

Thanks,

 

Vince

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:)

I have a 2 week old 2005 Envoy XL. I would have to agree with you on the rear air. I have never had a GM or a car (sorry, truck) with rear controls, and I guess that our trucks have the same controls.

 

I figure that the pedestal knob that reads 3-2-1-0-R is just a vent fan control knob that does not control temp. I have found that when you place this knob in the "R" position and adjust the rear seat controls to high and hot, the temp. of the rear air does get hotter, well at least warmer.

 

I am guessing that the only temperature controls for the rear air are located in the 2nd row.

 

I am using only my own logic for this, and therefore I may be completely wrong!

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Yes, you are right the temperature controls are in the 2nd row. However, regardless of which control is used the front or 2nd row the heat does not get any warmer.

 

Vince

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Vince,

I agree that the rear heat is not cutting it. Please post any new info you recieve from the dealer, as will I.

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They still don't have that fixed yet for 2005? I have the same problem with my 2002 Trailblazer EXT. Front and rear controls can be set to hot, but it only blows cold air. It has been like this new.

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Sounds like a circulation issue. The rear heat uses coolant to heat, just like the front. Maybe there's a valve issue, or just a low flow issue in the system. I know some other makers use an auxilliary pump to move coolant to the rear heater core.

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The following TSBs (2) have been issued, Bring it in for service

 

Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch) #03-01-39-007 - (May 29, 2003)

Air Conditioning (A/C) Inoperative/Intermittent, A/C Blows Warm Air (Replace A/C Low Pressure Cycling Switch)

2003 Cadillac Escalade, Escalade EXT, Escalade ESV

 

2002-2003 Chevrolet TrailBlazer, TrailBlazer EXT

 

2003 Chevrolet Avalanche, Silverado, Suburban, Tahoe

 

2002-2003 GMC Envoy, Envoy XL

 

2003 GMC Sierra, Yukon, Yukon XL

 

2002-2003 Oldsmobile Bravada

 

2003 HUMMER H2

 

Condition

Some customers may comment that the A/C system is intermittently inoperative or blows warm air.

 

Cause

An intermittent inoperative (open) A/C low pressure cycling switch may be the cause. This is an intermittent condition and temperatures may play a critical role if the vehicle is in the failed mode or operating as designed.

 

 

 

 

 

HVAC System Inoperative for a Drive Cycle, Poor HVAC System Performance in High Ambient Temperatures (Update HVAC Control Module Software) #02-01-39-005 - (Sep 23, 2002)

HVAC System Inoperative For A Drive Cycle, Poor HVAC System Performance In High Ambient Temperatures (Update HVAC Control Module Software)

2002-2003 Chevrolet TrailBlazer, TrailBlazer EXT

 

2002-2003 GMC Envoy, Envoy XL

 

2002-2003 Oldsmobile Bravada

 

Condition

Some customers may comment about no cold air from the heating, ventilation and air conditioning (HVAC) system during a drive cycle. This concern may occur at any time during the drive cycle and at any temperature setting. The HVAC system operation returns to normal after the vehicle has been keyed to off and restarted. This concern is intermittent and most likely to occur on hot days. This concern may be found on vehicles equipped with manual (CJ2) and automatic (CJ3) HVAC systems. Other customers may comment about poor HVAC system performance in high ambient temperature conditions. This concern may be present in automatic (CJ2) HVAC systems only. An HVAC control module software update was put into all production vehicles beginning in September 2002. Vehicles built in September 2002 and earlier may need this software update.

 

Correction

Update the HVAC control module using software available through GM Access beginning September 9, 2002. The update will be fully available October 7, 2002 to all dealers on TIS 2000 CD version 10. This software update addresses both the intermittent no cooling and the poor performance concerns. If the software update does not correct the concerns, perform the HVAC Diagnostic System Check and repair as necessary. If the HVAC control module is replaced with a part from GMSPO, make sure the module has the latest software update. The module may need to be updated even though it is a new part.

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Everything I see on those TSB's are related to no cold air, I believe that this thread is about no warm air coming out of the rear vents, that is what is wrong with mine.

 

It blows cold air just fine, but when it is 20 degrees outside I want it warm.

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Everything I see on those TSB's are related to no cold air, I believe that this thread is about no warm air coming out of the rear vents, that is what is wrong with mine.

 

It blows cold air just fine, but when it is 20 degrees outside I want it warm.

 

 

 

 

 

Bring it to the dealer, thats what a warranty is for.

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Problem solved :D the dealer changed the outside air temp sensor (p# 15047946 sensor# 9.770) and the problem was solved. The rear heat takes longer to get hot then the front heat, but it does get hot, so I am happy. The round control knob on the pedestal in 1-2-3 mode, changes the fan speed and tries to match the temp to the front temp setting, in R mode, temp will vary depending on the rear control setting.

 

Dont know if the a/c still works, but for now I have heat :confused:

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Problem solved :D  the dealer changed the outside air temp sensor (p# 15047946 sensor# 9.770) and the problem was solved. The rear heat takes longer to get hot then the front heat, but it does get hot, so I am happy.  The round control knob on the pedestal in 1-2-3 mode, changes the fan speed and tries to match the temp to the front temp setting, in R mode, temp will vary depending on the rear control setting.

 

Dont know if the a/c still works, but for now I have heat :confused:

 

 

 

 

Glad you got the issue resolved. Thanks for sharing the fix.

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My wife's Envoy XL does the same thing. Her's is a 2003 and unfortunately, out of warranty. The part appears cheap enough (about $15), but does anyone know where the heck it's located? It's worth the chance to just replace it.

 

Thanks for the tip and the help.

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