Envoy HVAC help

[trouttrooper]

Didn't really get much help at the forum for this platform so I thought I'd run it by you guys.

2003 GMC Envoy XL: 4.3l, 4x4, 176,000 miles, manual HVAC dual climate control.

We've only had this for a little over a year now and I've been slowly fixing all the little issues it came with. I swear some people just don't know how to take care of things. On the plus side the price was substantially lower because of all the little issues. Nothing complicated or expensive for a DIY'er and I've got 95% of the issues fixed.

Anyway, here's the issue I'm not sure on what to replace. The passenger side temp control will occasionally act up. When the selector near or at the hottest setting (all the way up) it will sometimes out of the blue start blowing cold air. I can "reset" it by sliding the switch all the way to cold and then back up to heat. It appears to be completely random, sometimes it will be fine for days then one day it will act up multiple times.

Is it the slider switch causing this or something else? I was going to try and fix it this past summer, but I don't use the heater in the summer and forgot all about this little issue until it started being 5 degrees outside.....oops

 

[WarWagon]

Pull codes. GM control panels are not reliable. Nether are the mode control door motor assembly. With the ignition on engine off do you hear a door hunting for position? Move the heat/cold control and listen for hunting in the entire range. Hunting noise is 100% for sure the door motor failing. Replace the expensive part first, otherwise replace the hard to change part first... Codes, if any, can help pin it down.

 

[THEFERMANATOR]

It is most likely the actuator itself going bad. Pretty common issue with this era GM to have this trouble. Many times you can fix it by simply pulling the actuator out, taking it apart, cleanign out the dried up grease, and relubing it with a high quality dialectric silicone grease. I've done a few now and this did the trick. What happens is over time the grease inside gets hard, and it causes it to lose cantact with the position sensor portion of the actuator, and it will default back to a nuetral position when this happens.

 

[trouttrooper]

No codes. I'll try removing and cleaning the actuator, I have an exploded diagram of the location of all actuators. I've already replaced the actuator for front vent/floor and the rear vent/floor. The rear one has pissed me off because the new one is now broken. Does the whole clicking thing when first start up because it breaks the shaft on the actuator during the start up "diagnostic". When I was installing that one I was testing the old one first and couldn't believe the incredible amount of torque that it was sending. I physically couldn't stop the arm to trick it into thinking it had reached the end of a cycle. It would only slip on the shaft when I reinstalled it and the blend door stopped it, I wasn't strong enough to make it slip even with tools. No wonder these things keep breaking the plastic teeth etc. I've been seriously thinking of putting a resistor in at the plug for the back one and putting the original actuator back in. It didn't have any broken teeth, just would spin on the shaft under extreme high torque. That freaking blend door isn't that hard to move, it only needs a small fraction of the torque that it sends.

 

[WarWagon]

At least the GM actuators don't break the doors clean off like Dodge stuff does... Yes, repeated banging is the actuator gone bad. A single thud is not. Under "load" say at high road speed the air flow can overpower a weak recurc door actuator and switch modes to fresh/outside air on you so it's not just the torque to move the door, but, TQ to move it under high speed airflow and hold it in position is the TQ that really matters.

 

[trouttrooper]

I removed the temp actuator, took it apart, and cleaned it up. I didn't see anything really wrong with it so I'm not holding my breath. That actuator was a bugger to get out since it sits directly behind a metal brace of the dash framework. Easy to get to/see, just the stupid brace in the way. Had to bend the brace out of the way with channel locks, not very easy.

Removed the rear actuator to see what was wrong. Just like the original, the gears are all ok, no missing teeth. It just pops/slips on the shaft of the main gear under high torque. I understand the need to overcome wind resistance, but I still think there is way more torque then necessary. Either that or the programming should have been better written to calibrate end stops and not put so much pressure when it bottoms out. As long as I don't select floor only or floor/defrost for the back it doesn't pop. For now it can just stay that way.

And the main reason I did all this today.....had to replace the blower motor resistor for the front. Fan speed 5 quit working.

 

[WarWagon]

Sounds like you need a big overhaul of the HVAC. Start with grounds and then maybe hit a junkyard for a control panel. The resistor failing is usually a motor that stopped running and overheated the resistor from no airflow. The blower motor should be replaced as well.

 

[JiFaire]

Mike, I feel for ya. these envoys are neat little SUVs, but they are a serious pita to fix.

Mine is 2003XL, 4.2l 4x4. 5speed in front fan is dead, airbag light is on, seat belt circuit is stuck, rear heat is erratic. Now my dashboard is crapping out... tach died a while ago, Speedo is going now. I'm going to pull it all out and redo the stepper motors.

I think the electrical system was done at harbor freight, but it was cheap and it runs good, so I don't complain.

Keep fixing, and start posting pictures, it will help me fix something sooner or later.

 

[trouttrooper]

Mike, I feel for ya. these envoys are neat little SUVs, but they are a serious pita to fix.

Mine is 2003XL, 4.2l 4x4. 5speed in front fan is dead, airbag light is on, seat belt circuit is stuck, rear heat is erratic. Now my dashboard is crapping out... tach died a while ago, Speedo is going now. I'm going to pull it all out and redo the stepper motors.

I think the electrical system was done at harbor freight, but it was cheap and it runs good, so I don't complain.

Keep fixing, and start posting pictures, it will help me fix something sooner or later.

2 possibilities for fan speed. Underhood fuse #35 40 amp, OR more than likely the blower resistor is bad, they are notorious for going out. It's an easy replacement job, under the glove box.

Gives a good how to.

This is the location of the passenger temperature control motor. They didn't think ahead too much on location, you have to bend the framework to get it out. I used a pair of channel locks, and a C clamp to bend it. Bit of a pain, took about 45 minutes to do.

 

[JiFaire]

Thanks, Pal. I will take a run at that resistor as soon as I get my stepper motors replaced.
Jim

 

[hookedup50]

I had all these problems and more with an 07 Traverse. Chevy said the HVAC boxes were deformed, causing the blend doors to bind, and would fix on my dime of course. I traded it in. I have been getting recall letters weekly for all issues mentioned and more in this thread. I feel your pain, as I had the Heat air assemblies apart more than I care to admit. I still miss that car.

 

[trouttrooper]

I really love the overall design of the Envoy XL/Traverse EXT. I can haul 7 people, the third row is actually doable for an adult, I get 20mpg on the highway, can actually tow a real trailer, have real 4wd, and is not as big as a full size SUV. Makes getting around parking lots so much nicer when I'm not having to deal with the extra width of a full size pickup/suv. Plus it fits in the garage with the Saturn as well.

It's too bad they rushed getting the platform on the road. My complaints have yet to be anything really mechanical or anything that would leave me stranded somewhere. Ours has a sunroof that I have siliconed into place because the track system broke. In looking how to replace it I decided it's not worth it. Gotta practically tear the entire inside out of the vehicle, PLUS it's basically a design flaw that's just going to break again sooner or later so why bother PLUS parts are expensive as hell.

I've heard of the dash in some going out, I feel your pain on that. It's not just on the Envoy/TB though, more of a GM cost cutting across the board, because I've heard of this problem on other platforms. I've been struggling with my HVAC system the most, and in my research it seems to be a design flaw in the BCM on how it calibrates the actuators. There's too much torque put on them and they self destruct during a calibration cycle.