bwoodry

Very nice JD.

I now understand much better what the mixing chamber valves etc look like and how they work.

I will now inspect mine with a great visual reference.

Thanks!!

John Rygg

I spent months trying to track this down, my mixing servos work great , but I still can cook dinner with the heat coming out of the vents. The final solution since I only drive my cab in the summer I disconnected the heater duct to the heat exchangers . Now the AC only has to deal with the nebraska heat!

MisterRisky

Hey John, Jason has said this over and over and I will confirm that it is true. If there is hot air coming out your dash vents, then it HAS to be coming through the mixing chambers. I was getting a little hot air from the dash b/c of the leaking paper hoses in the floorboard were allowing heat to heat up the whole HVAC unit up front. The vast majority of the heat was coming because of the loose servo screws allowing the mixer flap to move, as shown in the video. David has mentioned previously about adjusting the controller arm. That's also a good place to look if you are blowing hot air.

jgrosjean

I found the cause! One of flapper doors in front of the blower motors which control the hot air was not fully closed when the motor reached it's limit. Adjusting the fitting on the motor arm fixed it, but it had to push quite hard to get it sealed. The main problem is that the foam rubber on the door is deteriorating with age. It is a complex arangement with foam sandwiched between metal plates and the door can not be taken out to be worked on. I may look for some high temperature foam to replace it in the future.
Access is not too difficult. Move the central electric panel to the fender and take out the firewall.
Access to the left screws on the firewall is much easier if the fuel filler hoses are removed. Make sure your tank is one half or less full before removing the bottom one. The covers in front of the blowers are held on by 4 clips and then slide up. The flap is then accessible but can not be taken out of the car unless someone knows a way to do it without removing and dis-assembling the whole unit.

MisterRisky

I was able to open my mixing chambers without loosening the firewall at all. Of course I used some really long forceps and had to pluck the clips out of the inner guts using a telescoping magnet after I would pry them off. It was a bit like playing Operation, the Wacky Doctor Game!

For those who don't remember Operation:
http://frn.sdstate.edu/Lending_Libra...tion%20365.jpg