Murray

My HVAC needs some work....whose doesn't right?

Right now the air comes out of all vents all the time and the heater valve is always open. This was not an issue when I got the car last fall. I mean up here September is the start of heater weather anyway. But now with summer coming I took a further look at it.

I was following the testing procedure in Wally's write up with a vaccuum tester.

Green, yellow, blue all hold vaccuum no problem. White leaks down slowly and orange leaks down quickly. OK so from this I would say that the heater valve is bad and the center vent actuator is bad. I capped off the center vent line to see if the other vent controls would now work. There was no change. Air out of all vents all the time.

I am doing something wrong????

One other thing... I tested the black line (there was already a splice in it). testing the line going up into the dash it would not hold any vaccuum. testing going the other way it was fine. Does this mean anything???

I am now totally confused (my wife says it doesn't take much). The lazy part of me says wire tie the heater valve closed and who really cares if all the vents blow air. I mean you can control most of those separately at the vent anyway. But I like things to work as they should so I want to understand what's wrong and I'll fix it from there.

The rest of the car is awesome and this isn't a huge deal one way or the other, but if its easy to fix.....

Any advice is appreciated. Even if its just to shut up and drive it!

Thanks

TheoJ

Hi,
Orange is the center comb flap. It is common that it leaks. You need to fix that to get proper (especially AC) airflow. White is the heater valve. Could be the membrane or the rubber elbow that links it. Just check directly at the valve below the airfilter assembly.

Is there enough vacuum when you closed off the orange line towards the vacuum switch assembly?? A low vacuum will obviously stop all vacuum powered operation. If you use a Mityvac, use it to check the vacuum on the supply hose from the brakebooster to the vacuum switch assembly. You might have a faulty check valve at the brake booster or some other leak.

The heater valve itself is often bad. So if the lever on the valve works (closes) it can stil leak substantially.

http://jenniskens.livedsl.nl/Technic...1/MyTip138.htm
http://jenniskens.livedsl.nl/Technic...4/MyTip431.htm
Regards,

StratfordShark

The black line feeds hvac console, so if you have leak in any of the separate circuits black won't hold vac.

I'm puzzled why black was spliced as it's accessible from where it joins 4 way distributor under air filter. Are any other lines spliced? Are the splices all leakproof?

Have you checked all solenoid switches in hvac console for leaks, as well as the lines which connect to the switches which you have tested?

Murray

The black was the only spliced before I started testing. How do I test the solenoid switches? Do I hook the vaccuum tester to the feeder line (black in th engine compartment) and just move the sliders?

TheoJ

Testing is pretty simple, remove ground from the switches, and check with the Mityvac (unplug the brown ground wire connection at the switch assembly). If the black vacuum line still does not hold vacuum you have a leak Unlikely though, but it happens.

regards

WallyP

"But I like things to work as they should so I want to understand what's wrong and I'll fix it from there."

Have you downloaded, read and re-read the complete HVAC paper from our web site? It includes a fair amount of info on how the system works...

The black line runs from the black/blue check valve located at the vacuum inlet for the brake booster. If you don't have good vacuum on the black line, nothing works.

If you have a vacuum leak on the white line, you will always have coolant flow, thus hot air.

Did you cap the correct side of the orange line? You must cap the vacuum, not the actuator.

The black line must supply a good vacuum to the solenoid bank. The lower lever must electrically control the solenoids to change the air flow. Your problem may be vacuum flow, electrical supply to the control head, faulty operation of the control head, electrical supply to the solenoid bank, etc., etc., etc.

As you say, you need to understand the operation of the system before you can find and fix the problem, and I commend you for that attitude. Look at what you have, and ask specific questions - there are several folks on here (such as Theo!) who have the knowledge required to help you - but we can't see the problem from where we are.

Murray

Hi Wally

I have got the HVAC sheets from your website and I have read it alot. I have also been going through Dwayne's pictorial of checking for vaccuum. I think it's one more time through the information to plan my attack step by step with what I expect should happen at each step. After all I was doing this at 2am (couldn't sleep) and probably not at my best problem solving.

I do have one question before I start again....What is the normal state for the vents to be in? If they are not getting/holding vaccuum are the vents open or closed?

Thanks everyone for the input so far. It really is a great forum and there is so much knowledge out there.

the flyin' scotsman

Murray....the 'normal state' for the actuators is described at the rear of the HVAC section in the WSM.

The Porsche design is fail safe for cold weather so the hot water valve is normally open.....hot air
the defrost defaults to open so you have a clear windshield etc etc

The black line that feeds vacuum to the system should be checked for supply.....engine running you should see ~20 inHg of vac

BIMMERMIKE

Hi Murray, I'm in the Hamilton area and can assist you. I've been through my HVAC many times and know it well.
Send me a pm and we can meet up.

Murray

PM sent. Thanks.

BIMMERMIKE

dont see any PM