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Replacing Climate Control Diaphragms

Replacing Climate Control Diaphragms

Mark Stephenson

The other niggling problem was with the climate control system. Don't ask me why, but both diaphragms that control the fresh air/recirculate flaps did not work. I verified with a hand vacuum pump that neither held a vacuum. Besides the obvious vacuum leak, this leaves the flaps in the fresh air mode all the time. It's like having a permanent Gardner Mod. It wouldn't be a problem in a more forgiving climate, but in the summer in Arizona, it's tough enough keeping the car cool without having to continually cool 110+F air. I tracked a couple used diaphragms down and waited for the opportune time to install them. This seemed like it -- three weeks ago. (Can you say shipwright's disease?)

Now, to know what part I'm talking about, put your head in the footwell and look over by the outside kick panel. As you scan up the kick panel, one of the first things you'll see is a gold-colored metal "can" with a tiny blue the first things you'll see is a gold-colored metal "can" with a tiny blue other side, too. As you can see, r&r is not going to be easy.

Disclaimer: I probably removed more than I needed to, as I fumbled my way through this project. I'll tell you what I removed, unless I later discovered it was totally unnecessary.

I started on the passenger side, removing all the under-dash covers. The glovebox is a good idea, too. I'm not sure it is necessary, but it does make access much easier. Next, you have the fuse box and all the other electronic gadgetry which is bolted to the front of the blower fan. Remove the lower nuts, but just loosen the upper one. It slides down and will hang by the wires. The fan and flap assembly is secured by one nut and one bolt. The nut is way up between the kick plate and the blower case. The bolt is pretty is way up between the kick plate and the blower case. The bolt is pretty obvious on the opposite side. Disconnect the wires from the inside side of the blower. Disconnect the pigtail (fan motor wires) that comes through the blower case on the other side. Disconnect the vacuum line to the diaphragm and the rubber air duct that connects the fan output to the big box of flaps and coils and levers and linkages behind the console. (I don't even want to think about that!)

Believe it or not, the blower/flap unit is now free. That didn't sound too hard, did it? As you wiggle it around, you won't believe me. It seems free,but you just can't seem to get it out. You don't want to yank too hard for fear of breaking something (and I eventually did), but it just seems impossible to remove. That is what baffled me for two weeks.

There are two flaps in the unit. One at the bottom opens to recirculate air. Unbeknownst to me there is another flap at the top. This one opens into theplenum fed by the cowl vent. If you carefully (very carefully) remove the cowl vent and drop down to look into the furthest recesses, you can see it in there. (I have found that gentle prying with a computer slot cover -- the little L-shaped metal piece that covers the slots in the back of a computer -- prying evenly around the outside of the chrome vent cover brings it up enough so that you can grasp the edges and wiggle it free.) Anyway,the two flaps are linked by an amazingly complex system of lever arms and rods, which are quite ingenious when you see it work. When there is no vacuum, the bottom flap is closed and the top is open. The top flap is round on the ends and the cutout in the plenum is the same shape, so when the flap is open it hangs up on the narrower part of the opening.

Here is the secret: You need to pull the bottom flap open with you hand. This closes the top flap and aligns it with the hole in the plenum. Sometimes it still takes a little fiddling, rocking, and rolling, but the unit will eventually fall out.

If only I had known that before I had removed the crash rail, the defroster/side vent ducts, the dash face, and many other nuts and bolts that looked important. When all else failed, decided to use a little light persuasion with a pry bar. I broke one of the flap lever arms. No glue I had would adhere to it. I took the smallest drill bit I had, with the intention of epoxying a small stiff wire inside the piece. I drilled from the fracture out one end, then drilled in from that end through to the other piece. Then I broke my drill bit off in the hole. It would have been a move of pure genius if I had planned to do that, but even as I cursed my misfortune I realized my good fortune. I just left the piece of drill bit in there an am planning on buying many cheap drill bits for similar repairs in the future.

Once you have the blower/flap unit out, replacing the diaphragm will be obvious. Take the time to remove the squirrel cage from the flap unit and blow it out with compressed air. I had half an inch of crud stuck to the outside of the motor. If you have some chewed up weather-stripping where the flaps close, you might as well replace it.

Everything goes back together the way it came apart. If you have a vacuum pump, check the operation of the flaps. Make sure they hold their position. When putting the blower/flap assembly back in, pull the bottom flap down, get it positioned, and loosely put the nut and bolt in place to hold it. Before you tighten things down, find all the wires and vacuum lines and connect them. Manually work the bottom flap a couple times to center the top flap in the cutout in the plenum. Once it is moving freely, tighten it down.

The driver's side is the same except that the rubber duct between the fan and the console box is a royal pain to get back on the fan. Working above the steering column was nearly impossible, but I finally managed to get it connected. I don't know if my duct was misshapen or what, but then the other side just barely reached the tubes coming from the central box. Trying to get those on we pulled the fan end off. This was real test of patience.

With what I and you know now, I think you could cut the passenger side r&r time down from 2-3 weeks to about 2-3 hours. Add about two hours to the drivers side for that stupid duct.

I surely hope this helps other listers, I still have my entire dash to put back together.


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