I've read a few posts about the vacuum system controlling the air flow doors. I'll definitely start by checking over these systems. My issue is a little different than most. If I switch the **** to vent, defrost, or off, everything works fine. But if I switch it to floor, air comes out on the windshield. Is it possible for the door to be getting jammed? If so, would it jam on defrost? Or would that not make much sense? 4x4 works fine. I won't have a chance to take a look at it for a few more days, so just trying to get more ideas about what the problem could be.

 

Hi sputtle, I just went through a problem like this on my 05 jimmy, what happened to me was my defroster valve broke , it's really a flapper door ...they call it a valve #20 on the picture I attached . anyway if you want to change it the right way it looks like the dash is coming out and your opening the heater box.....might as well change the heater core while your there because ...well your there and if it started leaking after you were in there and closed it all up that would suck. The part is available , I'm in Alberta Canada and they said 5 days from the states @ $28.00. This is what I did once I removed the lower trim panels. with the truck running I could see all the vacuum actuators working (drivers side) when I when through the different settings so I disconnected the actuator for #20 grabbed #19 and moved it...it was quite loose and moved like the flapper shaft was broken just on the other side of where the shaft enters the box. I took out a half dozen or so screws item #8 ...as many as you can get...including the one just around the corner between the box and the inside firewall, I then pried the box open and jammed a couple deep sockets about the diameter of my pinky to hold the two halves apart...with hemostats I could now reach the broken door and pull it out..I still couldn't get #19 and the partial shaft out the hole in the box so I took a dremel tool and cut a piece of the box out leading to the hole and removed #19 and the broken shaft. Now I didn't order the part yet so I used good structural adhesive to fix the shaft and then drilled a 3/32 hole on an angle through where the break was, dipped the drill bit in super glue ran it back into the hole I drilled and cut off the bit shank leaving the bit through the break like a pin in a broken bone , fished the door back in put it all back together and patched the hole in the heater box with a piece of plastic. works a hundred percent....there was no way I was going to tear out the dash for a $28 dollar part....that I didn't buy anyways....funny thing is ...is that after I finished I thought of taking pictures....... It could be your actuator though.....if your luckier than me.....I forget if that actuator opens the valve or closes it.

 

That does make a lot of sense. I think I'll check that out first. I did hear a loud pop shortly before it stopped working, but I didn't think much of it. Thanks for all the info!

 

I didn't know at the time , but there is a big thread on this forum of other guys dong the same thing with pictures on how they cut the box open ....do a search and there should be a ton of good info for you.

 

Well I started working on this today. I don't know how the hell you got that screw out that's up against the firewall. I'm going to get a 5.5mm wrench and try that. And I can't seem to figure out how to drop the blower and all. Which I don't want to do anyway, if I don't have to. So far, Jimmy 1, me 0. Pretty sure the wrench will work though.

 

Finally got it fixed! Strangrock, thank you so much, your explanation is eventually what allowed me to fix it. Mine broke right in the same spot. I drilled through and used a nail for support and JB welded it together. Worked like a charm.

I did have to cut out a chunk of the assembly just to get at it. But that's ok. I'll also JB Weld the piece back into place. Might leak a small amount of air, but that's no big deal.

 

Awesome bro , glad it could be helpful.