How to replace Rear Heating & A/C assembly?

[Mike534x]

Does anyone know what's needed to replace the whole rear heating and A/C assembly hidden behind the passenger side panel on the Ext. Trailblazer? When we bought the truck it wasn't working, so I loosened the 4 screws to pop off the panel to inspect the actuators and I noticed the power connector going to the assembly was disconnected and we noticed one of the actuators was missing as was the plastic piece that's connected to what I'm assuming is the internal blend doors. I see why they disconnected it since I can only assume it was broken off from an attempted repair. I do have a whole new assembly pulled from a totaled Ext. Trailblazer, there are a few bolts and I think quick connect HVAC (?) lines right above the resonator into the assembly from underneath the truck.

I guess my biggest concern is, are there any guides to doing this, what fuses if any need to be pulled, and does the rear actuators need to be re calibrated, or anything else I should know before I start pulling this sucker out. It doesn't seem too difficult, but it doesn't seem like something that's been replaced on these trucks either. I know the actuators are fairly common to go.

Grabbed an image of it off Google.

 

[C-ya]

If it were me doing it, I would look at the one that is out and try to identify every place that it mounts or has a screw/bolt through it. As far as fuses, I would just disconnect the battery. Be prepared for all the actuators to recalibrate. Your throttle body will recalibrate, too, so you may as well clean it - especially relevant on the I6. [ETA: Just saw your sig with the 5.3 in it. My truck is basically the same as yours, just more miles! They are not as picky on battery disconnects because they don't get dirty like the I6 does.] I'm guessing you have had the A/C discharged, right? You'll need to get it charged back up when you get it all back together. I can't see them being quick-connect, but maybe the heater hoses are.

 

[Mooseman]

I had to take mine apart to replace the heater core. It was a pita. I had to replace part of the hoses because of a design change but that won't be a problem on your non-'02 EXT. The A/C may be a problem to disconnect the lines due to corrosion.

 

[Mike534x]

If it were me doing it, I would look at the one that is out and try to identify every place that it mounts or has a screw/bolt through it. As far as fuses, I would just disconnect the battery. Be prepared for all the actuators to recalibrate. Your throttle body will recalibrate, too, so you may as well clean it - especially relevant on the I6. [ETA: Just saw your sig with the 5.3 in it. My truck is basically the same as yours, just more miles! They are not as picky on battery disconnects because they don't get dirty like the I6 does.] I'm guessing you have had the A/C discharged, right? You'll need to get it charged back up when you get it all back together. I can't see them being quick-connect, but maybe the heater hoses are.

Oh yeah it is the same truck! Alright, if its just the battery then that's no problem. I actually did clean it, wasn't much dirt but didn't seem to hurt to do it while doing the plugs over the summer. I was actually trying to figure out what the best way was to discharge the system, I was thinking of just loosening one of the hoses going to the rear core, unless there's a better way of doing it. Maybe the hoses aren't quick connect....I'll need to recheck it once the weather clears. We probably won't get around to actually working on it until next week, still trying to call around and see who has the best quote for getting the system recharged once we start.

I had to take mine apart to replace the heater core. It was a pita. I had to replace part of the hoses because of a design change but that won't be a problem on your non-'02 EXT. The A/C may be a problem to disconnect the lines due to corrosion.

Ouch....that looked like a nightmare to deal with. I'll have to look at the A/C line again, they didn't seem to be in bad shape, I was able to loosen the bolt enough to where you could hear it hissing and seemed like it would come off if I continued.

 

[C-ya]

@Mike534x , I wouldn't just crack the line and let the freon escape. I'm not a green weenie or tree hugger, but that's kinda silly to do that, both from the environmental point of view and from your financial point of view. When I had my heater core replaced, I had it sucked out and held until the job was over. I didn't want to have to pay for 2.8# of freon. They don't just give that stuff away. Yeah, it's cheaper than R12, but why pay if you can use what you already have?

 

[Mike534x]

@Mike534x , I wouldn't just crack the line and let the freon escape. I'm not a green weenie or tree hugger, but that's kinda silly to do that, both from the environmental point of view and from your financial point of view. When I had my heater core replaced, I had it sucked out and held until the job was over. I didn't want to have to pay for 2.8# of freon. They don't just give that stuff away. Yeah, it's cheaper than R12, but why pay if you can use what you already have?

Oh I wasn't planning on just letting it spray all over the place, wasn't sure if I could attach something to the hose to contain all of it. Still trying to find a place that isn't going to charge an arm and leg to have the system recharged.

 

[C-ya]

Oh I wasn't planning on just letting it spray all over the place, wasn't sure if I could attach something to the hose to contain all of it. Still trying to find a place that isn't going to charge an arm and leg to have the system recharged.

You have to have special equipment to contain it. Just call around to the local shops and see what they would charge to do it for you. When I was going to do my heater core myself, I got a quote from a private, local shop that said he would do it for $50. Not too bad, considering I'm taking his tech's time twice. It ended up getting done by a friend who worked at the local Chevy dealer. He was moonlighting out of his garage and charging much cheaper rates. He was able to get the freon out and held until he finished the repair job. I ran by after work one day to get the system recharged as I needed the truck as soon as he finished it but before he could get the freon back in.