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91 300TE 4matic
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Discussion Starter #1
I recently purchased a 91 300TE in pristine condition. Everything works except for I can't redirect air from anything except for the defrost and side vents. The AC works, heat works, but it always comes from the defrost and side vents. After reading through the forums here, I removed the climate control unit and resoldered the contacts on the buttons. This didn't help, so I'm assuming it's a vacuum problem.

Everything I read refers to removing the glove box to get to the vacuum tree. I happen to have the optional airbag in place of the glove box. Does anyone know how to check the vacuum tree with the air bag? What do I have to remove or disable before starting?

Any hints, tips, and suggestions would be welcome.
 

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91 300TE 4matic
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Discussion Starter #2
Well I poked around a bit and found the solution. Right in the middle underneath the dash is a hole. Fairly far up is a 10mm hex head bolt that extends all the way through the airbag bracket into the dash. Remove that bolt and the entire airbag assembly pops out.

I was able to get to the vacuum tree and test all the modules. They checked out fine. All held 25 in. on a pump. I then checked vacuum into the tree. No vacuum at all there. I was able to verify by using the pump to apply vacuum to the tree and all the buttons worked allowing the center vents and floor vents to work.

Working back to the vacuum check valve under the hood, I bypassed that with a piece of vacuum hose. Everything worked again. I've ordered a new check valve and hope that's the problem.

One thing I don't know about is the second hose coming out of the check valve. It's red with a blue tracer. The hose to the top of the vacuum tree is green with a red tracer.

Does anyone know what the red vacuum hose does?
 
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