The switchover valve is behind the right lower corner of the dashboard, tie wrapped to the support member. It can be reached with some effort by removing the glove box liner. The rightmost a/c vent and the air sampler should come out as well, for better access. It can also be reached from below by removing the dash underpanel. Of course, if you're going to remove the entire dash, access is no problem.

There are numerous colorful vacuum tubes which terminate on the valve. There's no substitute for a vacuum testing tool like a Mityvac if you have a problem with Tempamatic. What you need to do is apply vacuum to each control and see if it holds. Note that some controls have two lines, both must hold. The various lines are:

Port 4/3 Green         Temperature Blend Flap (Y'd onto two ports.)
Port 5  Red               Heater Valve
Port 6  Red/Blue       Defroster flap
Port 7  Red/Yellow    Defroster Flap
Port 8  Green/Yellow Outside Air Flap
Port 9  Green/Blue     Outside Air Flap
Port 10 Green/Yellow Leg Flap

Vacuum source is the Green/Red line Y'd to the white manifolds...make sure you're getting vacuum, or the system will always blow hot.

I had two leaky pods...the Defroster Flap and the Temperature Blend Flap. I also replaced the heater valve, because it was an opportune moment.

The third photo shows the leg flap control and the outside air blend flap. These are one in front of the other, roughly located behind the ashtray. Obviously, the upper console has to come out to service them. The only trick to this is that there are two screws in the center vent that hold the console in place. The louvers must come out to remove these screws.

The fourth photo shows the temperature blend flap control and associated rheostat. The only way to access these controls is to remove the entire dash cover. Because of the difficulty of access, both the vacuum pod, the rehostat, and the associated rubber connectors should be replaced together.

The final photo is the defroster flap control in situ. It's wedged in behind the ignition switch. To remove it, you must unplug the wiring harness from the ignition switch. The harness will pop right off, but only if the ignition switch is in the ACC position. 

The dash is back together. Unfortunately, the job had to be done twice because the first time, the heater still didn't work correctly. Tracing everything out again, the problem turned out to be the five port vacuum switchover valve (the big valve on the right side of the the dash, below the passenger side vent. It had an internal air leak. Once this was diagnosed and replaced, the system began to work correctly again. Moral: check all the vacuum connections, vacuum pods AND the switchover valve before reassembling. 

The center section is a slightly different color (not as dramatic in real life) because the vinyl was torn, with chunks of the underlying foam breaking away. I used epoxy to fill the voids, and semi-gloss spray paint to finish it. 

The dashtop is a Coverlay. The fit was reasonably good. The trick to getting these right is to use folded over cardboard between the windshield and dash cover to  pin it in place until the adhesive dries. The fit isn't perfect, but it beats an old cracked dash top.

I'm using a Lincoln flux welder, which isn't ideal for sheet metal repairs, but a little patience always wins the day. The key to flux welding thin material is to keep moving to prevent the plasma from burning through the metal. If the work is getting too hot, remove the torch and allow things to cool. Where possible, using a heat sink behind the work can also help. 

The first step is to cut away rust-weakened metal. As you can see, there is much more rust than was apparent before I started cutting. Once the area is cleaned up, I will trim it to a rectangular opening to simplify shaping the patch. I will also remove all the loose rust that I can reach on the inside and prime.

I made a rectangular patch out of 4130 18ga steel. Since I'm not fully shaping the patch, I needed to extend the jack tube. I do this by welding a length of 3/4" black pipe to the end of the tube (don't attempt to weld galvanized material unless you know exactly what you're doing). I make a matching hole in the patch using a 1 3/16" chassis punch, then slide the patch over the pipe. I only grind the metal to it's final shape after the hole is correct. 

When the fit is right, I tack weld the patch every inch and a half around the edges, and then weld it to the extended jack tube. Next I use a cutoff tool to reduce the jack tube flush with the patch. Finally, I weld around the edges. In the photo, you can see that I've left off a piece at the top of the patch. This is because I didn't feel I could get as good a fit if I did it all as one piece. A second "L" shaped patch now fills this part of the repair. Finally, I work the welds flush with my cutoff tool. 

I coated the completed patch with Bill Hirsch's Miracle Paint, which is a very tough moisture cured urethane primer. Once the primer is dry I will apply a thin coat of plastic filler to produce a smooth surface, ready for paint.
 

I had a huge problem with the hood latch. In the middle of fettling the fenders, the hood just wouldn't release. I could hear the catch moving, yet the hood wouldn't budge. Fortunately, the grille was removed, yet access to the lock mechanism was still not easy. What I ended up having to do was to slightly bend up the lip of the hood, and use a 10mm wrench to remove the two bolts securing the top plate of the latch. Even with the hood open, it took some work to unlatch the plate.  I eventually managed to get it to let go, but don't ask me how. Aside from the mystery of how this happened, the cable is now stretched to the point that I need to replace it. Another lost day.

I also replaced the door lock mechanism in my left door. Once again, I have a car than can be locked. The mechanism is an incredibly tight fit. I'm guessing that at the factory, the door innards must have been installed prior to fitting the door skin. I left a lot of my own skin inside the door manipulating everything into place. And another lost day.

What I haven't done is replaced the doors, although I did buy four inexpensive used doors. As it turns out, the rust in the doors is easily fixable, which makes keeping the old doors a reasonable choice. The used doors haven't gone to waste, as needed a lot of sundry hardware....locks, window motors, door check straps. Enough to have made the purchase worthwhile. When I'm done, I may put the shells on E-Bay, or maybe just stash them away against the day I need them.

I coated the entire inside of the trunk with Miracle Paint, it should hold up a while longer. Just a few minor rust spots. Next comes knocking out a few minor dents and a skim coat of plastic here and there but wait... how come my feet are wet?

The front passenger floor extension turned out to be a layer of rust between two layers of rubber. A job for my Lincoln welder. Ever get to the point in a project where you wonder why you started it? Not too proud of these welds. They're strong enough, stronger than they look, but ugly. The material had some rust and dirt, not to mention residual paint and seam sealer. As a result, there was lots of spatter and a sputtering arc. It'll have to to do for now, out of sight, out of mind. The underside will get a layer of plastic and fiberglass, no water will reach the patch.

One of the problems I had with the central locking system was that it wasn't being triggered from the drivers door. The problem turned out to be that the lock mechanism itself was partially frozen with rust. The story of how to replace an entire lock mechanism is beyond my photography skills. It took a full day to worry it into place. But the lock cylinder itself was damaged as a result...the extension tang was partially broken off, from trying to turn it against the frozen mechanism. Two ugly choices: one was to install a salvaged cylinder, which means having a different key, or buying an expensive new one with matched key from the dealer. I took the middle road: I salvaged a lock cylinder from my spare door, removed the extension, and installed it on the old cylinder. For anyone who has to service their cylinder, here's how. First pry out the two plugs on the door jamb. The big one is actually a holder for the electrical connectors. Behind the lower one is an allen screw than retains the lock cylinder. Loosen this. Once this is done, insert the key in the lock and turn as if you are unlocking, and as you do that, push the key towards the rear of the car. The lock cylinder will slip back about 3/16", and it can be pulled straight out. If you need to replace the extension, just drive out the little roll pin.