Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

1 - 16 of 16 Posts

·
Registered
2003 gmc envoy_sle_xl
Joined
·
68 Posts
Discussion Starter #1
Ok, I'm not sure if this is a real problem or just me. I searched through the threads but could not find the same specific thing ( I probably did not look hard enough)

Here's what's going on, now that the seasons are changing it's getting colder outside and the climate control is acting strangely. I do not have the heat or ac blowing from this vent but not that vent problem, or side to side variation. It seems as if the climate control is confuses as to the actual internal cabin temperature. Regardless of the temperature outside the hvac must think that the cabin is on fire because it will run the ac full blast from whatever vents it thinks it should, or whatever ones I have selected. Now on a hot summer day this isn't too bad, but on a brisk fall morning when it's only 50 outside, having the AC run full speed doesn't do much to the areas not covered by the heated seat. If I turn the temperature up it will calm down and either turn the heat on or just quit blowing. Any ideas? Is there an internal cabin temperature sensor somewhere that could be on the fritz?

Thanks!
 

·
Registered
2002 chevy trailblazer_ltz
Joined
·
96 Posts
Ok, I'm not sure if this is a real problem or just me. I searched through the threads but could not find the same specific thing ( I probably did not look hard enough)

Here's what's going on, now that the seasons are changing it's getting colder outside and the climate control is acting strangely. I do not have the heat or ac blowing from this vent but not that vent problem, or side to side variation. It seems as if the climate control is confuses as to the actual internal cabin temperature. Regardless of the temperature outside the hvac must think that the cabin is on fire because it will run the ac full blast from whatever vents it thinks it should, or whatever ones I have selected. Now on a hot summer day this isn't too bad, but on a brisk fall morning when it's only 50 outside, having the AC run full speed doesn't do much to the areas not covered by the heated seat. If I turn the temperature up it will calm down and either turn the heat on or just quit blowing. Any ideas? Is there an internal cabin temperature sensor somewhere that could be on the fritz?

Thanks!
i had this issue from the day i own my truck, it seems that this is a normal issue, but when i turn the heater once, the HVAC memorize its last setup, so it blows directly cold air (internal temp) then start to warm, the A/C compressor work immediately also to remove the humidity in the cockpit. you will recive many reply to this thread, hope will have a clearer image
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
Assume you have the digital automatic controls? There is an internal cabin temp sensor near the driver's left ear. Looks like a microphone grille. Tiny squirrel cage fan blows air past the sensor. Take off the B-pillar trim by prying it off and see if the fan is spinning nicely.

I also assume you have a decent outside air temp display on the control module. If that is bad, it will confuse the entire system.

Only a dealer's tech tool or a high end scan tool can communicate with the HVAC control module and obtain all the sensor readings to see if any of them are whacked. Might be worth calling independent mechanics to see if their tool can do that, and pay for some diagnostic time.

You can also try a module reset, which sometimes works - hit REAR defrost, FRONT defrost, and MODE all at the same time. Then turn off the defrosts, and his AUTO mode and see if it behaves better. It's like a Windows CTRL/ALT/DEL three finger salute.
 

·
Registered
2003 gmc envoy_sle_xl
Joined
·
68 Posts
Discussion Starter #4
i had this issue from the day i own my truck, it seems that this is a normal issue, but when i turn the heater once, the HVAC memorize its last setup, so it blows directly cold air (internal temp) then start to warm, the A/C compressor work immediately also to remove the humidity in the cockpit. you will recive many reply to this thread, hope will have a clearer image
It's not that it starts cold then gradually warms up, it will be find then all of the sudden kick to full AC!

Assume you have the digital automatic controls? There is an internal cabin temp sensor near the driver's left ear. Looks like a microphone grille. Tiny squirrel cage fan blows air past the sensor. Take off the B-pillar trim by prying it off and see if the fan is spinning nicely.

I also assume you have a decent outside air temp display on the control module. If that is bad, it will confuse the entire system.

Only a dealer's tech tool or a high end scan tool can communicate with the HVAC control module and obtain all the sensor readings to see if any of them are whacked. Might be worth calling independent mechanics to see if their tool can do that, and pay for some diagnostic time.

You can also try a module reset, which sometimes works - hit REAR defrost, FRONT defrost, and MODE all at the same time. Then turn off the defrosts, and his AUTO mode and see if it behaves better. It's like a Windows CTRL/ALT/DEL three finger salute.
Yes I have the digital controls, the outside temp display works good, it does seem to get stuck once in a while when it's really hot outside! It probably would be worth replacing.

I've often wondered what that thing by my ear was, I'll have to take a look, then call around.

I have tried the reset (when the outside temp gets stuck) and it always does the same thing.

Thanks!
 

·
Registered
2009 chevy
Joined
·
6,431 Posts
Just me (and the simply way I think), but if the exterior temp gets stuck sometimes, that's where I would start.

If we know one thing is bad, don't ignore it and go looking for something else.
 

·
Registered
2003 gmc envoy_slt
Joined
·
8 Posts
I had a similar problem with my HVAC. The unit would act possessed and do what ever it wanted. I could turn it on and get nothing and then 10 minutes later while driving down the road it would kick on at full blast. I posted the problem on another forum and found it was a control module that is located under the glove box. Got the part and replaced it. HVAC works like a charm now.
 

·
Registered
2006 chevy trailblazer_lt_ext
Joined
·
3 Posts
Is there a way to convert from the digital automatic system back to the standard dual zone system?
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
Should the truck be running when I do the "Reset"?

Assume you have the digital automatic controls? There is an internal cabin temp sensor near the driver's left ear. Looks like a microphone grille. Tiny squirrel cage fan blows air past the sensor. Take off the B-pillar trim by prying it off and see if the fan is spinning nicely.

I also assume you have a decent outside air temp display on the control module. If that is bad, it will confuse the entire system.

Only a dealer's tech tool or a high end scan tool can communicate with the HVAC control module and obtain all the sensor readings to see if any of them are whacked. Might be worth calling independent mechanics to see if their tool can do that, and pay for some diagnostic time.

You can also try a module reset, which sometimes works - hit REAR defrost, FRONT defrost, and MODE all at the same time. Then turn off the defrosts, and his AUTO mode and see if it behaves better. It's like a Windows CTRL/ALT/DEL three finger salute.
I have the same issue with my 03 TB EXT. My question is:

Should the Truck be running when I do the "Reset"?
Thanks
Buddy
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
2003 Trailblazer EXT Window issues, HVAC issues.

Hello all. Boy where do I start. I have been in search since Nov 2009 of a Master Window Control Module that seems to be on National Back order for ever. I have located several on e-bay but I am afraid to get one since I heard that they need to be "programed" to that specific vehicle and must be programmed through the dealer. That's issue #1. Here is issue #2. Now my Heater/AC controls do weird things. I have the dual zone Digital Climate system. Ya know...two big knobs, Digital display in center, fan speed control "rocker" switch to the left of the display... ya know what I am talking about now?? anyway, if I want to manually increase the fan speed... nothing happens. Then... if I shut the truck off and re-start after a few mins... it sometimes blows real hard like it should, or somewhat faster than it was. I dunno??? Any ideas? I recently had the dash out to replace the radio with a nice new Pioneer head unit. I do have some components up under the dash behind the glove box area, but I took care as not to get in the way of anything I thought was important. I read that there is some sort of "control module" up under there for the fan... HMMMMM I wonder if I touched something there. Anyway, thats my issues with my Trailblazer. Thanks to anyone who would have a clue what I should do.
Thanks
Buddy
 

·
Registered
2003 gmc envoy_slt
Joined
·
357 Posts
I don't know about #1 but for #2, you need to replace the blower motor control module. Do a search on those words and you will find lots of info. You might just double check first that you didn't mess up the wiring to the module when you did the other work.

C.B.
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
ok. I will go back in and see if I have a Radio Component in the area. It happened as I was doing the Radio install.
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
Hello all. Boy where do I start. I have been in search since Nov 2009 of a Master Window Control Module that seems to be on National Back order for ever. I have located several on e-bay but I am afraid to get one since I heard that they need to be "programed" to that specific vehicle and must be programmed through the dealer. That's issue #1. Here is issue #2. Now my Heater/AC controls do weird things. I have the dual zone Digital Climate system. Ya know...two big knobs, Digital display in center, fan speed control "rocker" switch to the left of the display... ya know what I am talking about now?? anyway, if I want to manually increase the fan speed... nothing happens. Then... if I shut the truck off and re-start after a few mins... it sometimes blows real hard like it should, or somewhat faster than it was. I dunno??? Any ideas? I recently had the dash out to replace the radio with a nice new Pioneer head unit. I do have some components up under the dash behind the glove box area, but I took care as not to get in the way of anything I thought was important. I read that there is some sort of "control module" up under there for the fan... HMMMMM I wonder if I touched something there. Anyway, thats my issues with my Trailblazer. Thanks to anyone who would have a clue what I should do.
Thanks
Buddy
ok... I bought a used Master Window Control Switch on ebay.........IT WORKS!!!!!!!!!
Forget that crap that the dealer has to program it. Now on to figuring out my possessed HVAC functions.
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
ok... I bought a used Master Window Control Switch on ebay.........IT WORKS!!!!!!!!!
Forget that crap that the dealer has to program it. Now on to figuring out my possessed HVAC functions.
Read all the posts with the same problem. I went to GMpartsdirect and ordered the module # 89018778. Lets see if that does the trick.
 

·
Registered
2003 chevy trailblazer_ls_ext
Joined
·
40 Posts
Fan speed control module

I had a similar problem with my HVAC. The unit would act possessed and do what ever it wanted. I could turn it on and get nothing and then 10 minutes later while driving down the road it would kick on at full blast. I posted the problem on another forum and found it was a control module that is located under the glove box. Got the part and replaced it. HVAC works like a charm now.
Yes. I replaced mine as well and that was my issue too. Now lets see what else can go bad...lol
 

·
Registered
2003 chevy trailblazer_ltz
Joined
·
9 Posts
hvac erratic

hello guys,
i have a 2003 trailblazer ltz with 6 cylinders, 230.000 km on it.
my hvac is driving me mad, because it goes continuously up and down with the temperature.
i set a temperature with the auto button and it normally works for some minute, then the temperature start to go down or up without staying where i wanted to.
i have a new temp sensor in the pillar, a new outside temp sensor, a new ignition switch, a new (from last summer) blower motor resistor.
i have searched through the threads but i am unable to find a solution.
sorry for my english but i am italian, living in Italy.
thanks to anyone for reading and maybe to help me..
thepeps
 
1 - 16 of 16 Posts
Top