Hey there, I already checked and there are a few threads out there talking kindof my problem...but I want to tell you the whole story:



I own a 87 TPI 5.0 with optional A/C and I only drove it home 400mls and now I try to fix anything which is broken or has to be done. So here is what I see:

I had no idea what kind of valve that was before finding these threads here: It seems like the previous owner dismantled the valve. So it is still there but not controlled anymore.

Here is a picture.






Now I learned that this should be vacuum operated and controls the coolant fluid to either run through the heater - or not. Since it got warm during my one and only run I guess the heater is always "on" now...

• What does that mean? Do I always get hot air inside if the fan is not in OFF? I do not expect any damages because everything is built to let it run through but if I need to manually switch the valve between summer and winter I might better fix the valve again

I have to add that I do see two other (now maybe related) issues:

1. I do hear the so called "hissing". BUT: Just if I get off the gas pedal...(I think it sounds more like a "sucking").

And 2. I do not have the A/C in operating state: the previous owner dismantled this as well. Meaning: all hardware is still there but no belt is installed, the overpressure switch is unplugged as well as the compressor clutch and well, my heater control valve is not for any control.



So maybe someone can tell me in short words what that means: Clearly, I do not have A/C. Is the heater control valve connected to the A/C-function in any kind or is it a different "problem" that the valve is only to operate manually (or is it "unplugged" because the owner did not want the A/C to be operating)? Could the hissing or sucking be coming from the missing vacuum hose to the heater control valve or might I have the same issue with the backside if my control panel (but the sound is not permanent! Only when getting off the gas (and car rolling))?



It is confusing. I think I can (for now) stay without the A/C but I would appreciate to get rid of the noise and to not have a hot heater during summer all the time when switching on the fan/blower...







And last thing: If I what to rebuild the valve I guess I need a totally new one and there is no "cap" I can just put on, right? Where would the vacuum hose go to? Directly to the A/C-control panel?

 

Go to the store and buy a new valve for under $20. Then, find the 2 hard small vacuum lines located by the fan motor on the firewall coming out of the harness. the line that connects to the NEW heater Control Valve connects to one of those two lines. The other line need to be hooked up to PORT vacuum.
You have a 50/50 chance on getting it right. Vacuum is behind the AC/Heat control panel that allows the operation of the heater control valve.

And YES you will have heat in the heater core if the valve is messed up ( which it looks like it).

 

All right. Got it. Thanks.



So I checked that today and I could find two vacuum lines coming out of the firewall (at a harness).



But both are somehow connected. I guess one of the previous owner did mess that up. The broken valve is not even the original one. It is a AUDI part.

So I'll order the new one.



The question is, what to connect with that. I tried to show you the hoses as they are in my car right now. I am not sure which of the two will go to the valve and what about the loose end then...


Pic will follow...