MsvlCSQuattro

I have an '87 4000 Quattro. The vacuum unit that closes the door to push air across the air conditioner evaporator does not work. Do I need to replace the little vacuum pump that it is attached to? If so, where do I get one and how do I describe it? I do not see it listed in my repair manuals.

MsvlCSQuattro

tufelhund

This whole system is run by vacume from your engine. There is a little vacume valve that controls the door based on temp/relative humidity. there is also a temp/humidity sensor (little black button thingy) right at the air inlet side with 2 wires going to the valve. Basicly when the a/c is off you get fresh outside air. with a/c on you get cold inside air.
try and hook it up like in the picture make sure you have vacume. hope this helps.

tufelhund

<center><img src="http://pictureposter.audiworld.com/78014/p8110055.jpg"></center><p>This whole system is run by vacume from your engine. There is a little vacume valve that controls the door based on temp/relative humidity. there is also a temp/humidity sensor (little black button thingy) right at the air inlet side with 2 wires going to the valve. Basicly when the a/c is off you get fresh outside air. with a/c on you get cold inside air.
try and hook it up like in the picture make sure you have vacume. hope this helps.

MsvlCSQuattro

That is the way mine is hooked up. What do you suggest now?

MsvlCSQuattro

I checked -- no vacuum!

tufelhund

<center><img src="http://pictureposter.audiworld.com/78014/p8110058.jpg"></center><p>trace your vacume line thru the firewall to the engine. the little round blue and black thingy is a check valve. Make shure the blue side is towards the firewall.
I would trace the lines to the intake and make sure you don't have broken or cracked lines.

MsvlCSQuattro

So far as I can tell the line looks ok. I pulled the hose off at the first junction (other hoses going into a plastic "manifold")between the check valve and the manifold. I could not feel any suction coming from the junction.

Whitjr

Maybe it's time to r/r a bunch of vac lines...

MsvlCSQuattro

Thanks. I'll get to it this weekend.

tufelhund

I have pretty much removed all of my emission control crap. Like the charcoal canister and related gas vapor recirculator garbage (Run's much better,Really!!) You might not get away with it if you have Cali tags.
Any way, do this... get a Tee fiting from local parts store and some new vacume line. Find the vacume line coming off the bottom of your intake boot. you can pretty much tap into the intake system any where for vacume. run the new line over to the check valve and onto the air valve.
refer to earlier picture.