scrnchr - it sounds like your heater door's broken. That's exactly what mine did - no air comes through the floor, so the system automatically switches to defrost (because the air has to go
somewhere). There's a TSB out there about the problem, but I think it's listed for a Tracker. Your local GM dealer should have it. I ran through the troubleshooting steps first, to make sure it
wasn't anything else causing the problem.
I did mine in the fall (2001 Blazer), and it took me maybe a week of on & off work. I probably only worked on it an hour or two a day, but it's still a pretty long job. I didn't take pictures of
my progress, and my memory about the process isn't 100%. I'll give you some pointers, from what I do remember:
1. Yes, the dashboard will need to come out. The whole thing. From the windshield to the steering wheel. Any attempts to shortcut this will just end up taking longer. Trust me on that one.
Just suck it up & get down to business.
2. Go to your local library and look for the Factory Service Manual for your Jimmy. The steps are not in order, so I'd follow along in the book & write a note with the page numbers in the order
you'll need to follow (e.g. You'll see a lot of "refer to X Removal Process section for X removal"). The FSM steps have (some) pictures, and the process is fairly intuitive.
3. I didn't have to pull my steering wheel, but I did drop the column. If I did this again, I probably would've removed the wheel for more clearance. I ended up with a scratch on my steering
wheel when getting my dash back on. If you've got one of the models with the bigger steering wheel, I'd consider removal to be a requirement. At some points, I put the parking brake on & moved the column shifter all the way down, to get more clearance on the top of the column.
4. You'll want to do the work in a place where you can open both doors & have 1-2 feet of clearance beside each open door. The worst thing that could happen is to get the dashboard removed &
find you don't have enough room to get it out of the truck.
5. You might also want to remove the A-pillars (very easy - they pull off) & throw a towel over anything you think you might scratch if the dashboard slips. There is metal protruding from
the rear of the dash, and it's fairly easy to put a deep scratch in paint or an interior panel.
6. Your 3 best friends in this endeavor will be: box of Ziploc sandwich bags, roll of masking tape, Sharpie. After I took a part out, I put the screws to that part in a Ziploc bag, wrote
the name of the part & the side of the truck it came out of on the bag, and taped the bag of screws to the part that came out. If you need a diagram of how the part goes in or where the screws go, write yourself a note & throw it in the bag. There will be a lot of screws coming out. A LOT. Knowing where they go is WELL worth the extra time in labeling.
7. Same goes with the electrical connectors. All of the wires in my Blazer's dashboard come from the fuse box on the left, and the main wire bundle runs down a plastic center channel bolted to the back of the dashboard. Don't try to take the plastic channel out - just cut the electrical tape holding the wire bundle. When I put the bundle back in, I used zip ties to get it back in the
channel. I also wrapped another layer of electrical tape around the bundle, just for the hell of it.
8. Label every single electrical connector that comes out. I didn't, and I regret it. You'll be amazed at how many of them there are. Also label where the connector goes on the dash. If you
want to take pictures to remind you later on, now's the time to do it. Take my advice on this one - I ended up spending over an hour on taking parts back out because I thought I forgot to hook up my passenger side door jamb interior light switch. As it turns out, I had to trace the wiring diagram to find out my Blazer doesn't have one of those (it's controlled by the exterior door handle). There was a connector, and a switch, but no wire. Learn from my mistake. Label your connectors.
9. If your dashboard speaker covers have screws like mine, you'll want to use something like this: http://www.harborfreight.com/cpi/cta...emnumber=92630
. I don't even think
there's enough room to get a stubby screwdriver in there, so that right angle driver is a lifesaver.
10. The top of the dashboard rolls forward, then lifts up. There's a J-shaped metal part on the bottom which goes around a peg coming from the body. You need to tilt the dashboard forward, so
the J clears the peg. You should be able to see it at the bottom of the dashboard assembly, above the kick panels. I think I ended up removing the kick panels when the dashboard went in, so I could see the pegs a little better.
11. The dashboard is difficult to maneuver, and it's a little heavier than I expected. Put both of your front seat/seatbacks all the way back, open the passenger side door all the way, and move
it out through the passenger door. If you have a helper on the driver's side or have removed the steering wheel, this step will be exponentially much easier. Since I did mine solo, I slid the
driver's seat all the way forward, to prevent the steering column from dropping too far down if I happened to drop the dash.
12. Here's what mine looked like without the dashboard: http://i40.tinypic.com/2m5knro.jpg
(sorry, shitty cameraphone pictures). Congratulate yourself.
You're about halfway done.
13. See the compartments in the middle with the foam around them? The heater door is in there. It will probably move back & forth easily with your hands, because the plastic at one of the
ends is snapped. If the part is completely intact, you should probably start swearing loudly now.
14. If I were you, I'd take a picture or draw a diagram of the way the door tab fits on the spring, on the left side of the heater box (on the outside). If I remember right, there was a little
trick to it. The door will take a little maneuvering to get in & out of the box, but just be patient & use your head. It's not really difficult.
15. Everything goes back in pretty much the way you'd expect it to. If you labeled everything like I recommended, this should be cake. The only tricky part I ran into was lining the dashboard
up with the screws on top. I took a straightened paperclip to poke threw the screw holes in the dashboard, to make sure they lined up with the screws on the body. If you can see in my picture,
the black rubber "flap" tends to cover the screw hole a bit, when the dash is on. I don't think there would be any harm in trimming it a bit so it doesn't cover the hole.
16. After you've got most of the electrical connectors hooked up & the dash in place, it would be a good time to pause. Start the car, so you can check your heater settings & other switches. In
the unlikely case you screwed something up, you want to know before you've tightened everything down.
17. Everything works? Awesome. Continue putting everything back where it belongs. When it's all back in, do one final test of all the dashboard switches, then bask in the glory of your