Hi,

I know, this Problem often appears in this forum, but I have some special questions.

I have the most common Problem with my Pontiac Firebird 1989 with 173cui V6 engine: My A/C is in defroster mode all the time.

So I know that problem appears when losing vacuum. While changing some vacuum hoses in the engine bay I recognized something: At the firewall there is a cable loom, where a vacuum hose is also bounded in. This vacuum hose wents to the main heater valve ( i'm not quite sure if this is the right name of that ). A second vacuum hose also goes into this cable loom, but it is cut off and so I have some questions:

1. Is this right, that the first vacuum hose goes from heater valve to cable loom?

2. is it correct, that there must be 2 vacuum hoses going to the cable loom?

3. and if so, where does this second vacuum hose go to? mine is cut

thank you for your help

greetz

 

There are 2 vacuum hoses in that bundle, yes. One of the will go to the heater valve, that controls whether you get hot or cold air from the vents. The other hose goes to the vacuum nipple on the back of the intake plenum to allow you to control which vents the air comes from.

 

Ok , thank you.

Where is the other side of the second vacuum hose connected? ( the one that is for the vacuum to control which vent the air comes from ).

The vacuum hose is cut at the engine bay's side, I hope it is ok on the control panel's side.

Very fast help, I thank you very much. Now I'm sure that coult be my problem...

 

The other side of that hose connects to the back of the Vent A/C control module inside the car. If you take it out, you'll see several different vacuum hoses connected to control the different "doors" in the vent ductwork to direct the air where you want it to go. IIRC, they should be color-coded as well. Moving the lever on the front of the controls changing the path the vacuum takes through the control body and therefore which "doors" in the vents should be opened or closed.

 

I am also having difficulty with this, my question is this:
1. With the Vent A/C control module out of the console and being able to look at it, I can put my ear next to the disc where all the diffferent color vacuum tubes are and I hear vacuum leaking through all positions. It makes sense that I would hear vacuum when in the off position, (I assume that this position is just open vacuum because it being in the off position and does not need any vacuum thus it is blowing it off, maybe I am wrong, probly am), but should I be hearing vacuum in all the positions and one in particular seems to be a just a little louder than others? (which one I don't know.) I have replaced all my vacuum lines from the cruise control tank to the heater valve, actually I had to buy a new heater valve as it was leaking coolant. The lines are typical as stated in post above.

H E L P !!!!! The car is in pieces and it is my DD. THANKS!!!

 

Sounds like you have a bad/leaking control module. Engine HATE vacuum leaks, so I can't see it being designed to be open when in the off position. I'd check my car for you since my interior is all apart, but I don't have an engine in it right now to provide the vacuum. I'll have to check my service manual when I get home tonight and let you know.

 

Thank you for the info 92RS Ttop-if you can confirm on the vacuum leaking, that would be great. I ordered the part from Advance Auto-cost about $21.00. Will be in tomorrow. When I took off this part, there is a small black plastic clip that holds the round piece on the back of the main piece which came apart as soon as I took it off the main control panel. RockAuto calls it an A/C vacuum control valve-part #1571350. Cost was around $13, but with shipping would have cost about the same as Advance and I would have to wait for it longer than one day as is the case w/ Advance. I will install it tomorrow night and repost. I sure hope this is it. BTW, do you know if there is anything else I should just replace while I have everything tore up in this area? I thought I would replace the light for the A/C control panel although it works now just fine. Any thoughts on that, let me know. Thank you again.

 

92 RS Ttop-yes, it was the a/c vacuum control valve. Put it in and walaaaa, vents switch like brand new. Thanks again for your help.