I have had the common problem of poor AC performance. I read all the earlier post about vacuum lead testing and bought the mity vac. I found good vacuum at the black tube going into the vacuum system valve monifold, but could not get a vacuum on the blue or yellow tubes. The white orange and green held a vacuum.

The yellow controls the foot well flat. I can see that and will replace the actuator.

Here's my question. Does it make sense to just disconnect the actuator arm for the recirculate flap and wire it up so I will always have air recirculate rather than bringing in outside air. My BMW has a recirculate button that I have not had off is 4 years. I hate being stuck in traffic and sucking in everyone's exhaust fumes. From my understanding of the system (which isn't saying much) this would be an improvement.

Any thoughts?

 

YES! I did this on my car. It's on permanent recirculate. Under the dash(air box) are the flaps. I cut of the flap that opens and closes. It's now on recirculate mode, but it will still suck air from the outside. So, get down there and tape-up the outside air hole. You will see it when you get down there. When you completely seal the outside air, then you will have complete recirculate mode(better than factory!).

I did all the full cold mods to my car. Here are some more.
1. Bypass that stupid heater core.
2. Plug-up the AC hose going to the glovebox.
3. Plug-up the feet AC holes(ones at each side).
4. I also took the dash off, so that I could also seal the defrost vents.
5. And, once you have the dash out. Open up the air box in the center console. It's got a cover that is held with clips. It has ALOT of flaps inside that stop airflow. Remove them all.

If you do all these things, you WILL have an ice box!

 

Do you remember whether you access the recirculate flap from inside the passenger footwell or from the top after taking out the blower etc. Once the recirculate flap is wired/taped open, how does any outside air get in? Any details you remember will be appreciated. I will be diving into this tomorrow. Thanks.

 

From the inside. Take off your glovebox and under tray. Turn on your AC so that the sound points you in the right direction. Remember, it's way under the dash so have a flash light. You will see a black cover with a flap in the middle. Push up on the flap to open it. Hold this flap open so that you can cut it off.

You can put something in there to hold it open(so that you can test if you need to do the other modes). I used a coke can to hold it open for about a week before I decided to go all the way. It made a huge change. But since I live in Miami, I had to do everything. That said, find something to hold that flap open. Drive around for a week or so, it might be all you need to get good cooling. Good luck.

 

To each his own, but if you destroy the HVAC system, the next owner will curse you and your family for four generations.

I would suggest that you just get the system working the way that Porsche intended - which isn't that hard to do.

For example, by the time that you get far enough in to tie the recirculate flap open, you are almost far enough in to fix it properly.

 

No, I think that the next owner will be cursing Porsche, for designing such a horrible system in the first place.

 

I made my HVAC go into recirc by routing an additional vacuum line to the recirc controller - thus applying vacuum all the time. An easy mod that can be reversed quickly if I ever sell the car.

hth-

 

I'm with Wally. About half the time we spend on this list is complaining about how previous owners screwed up the car. Jeeeez, you mean a vacuum pot didn't last 17 years....man Porsche
sucks,.....give me a break! If your going to
fix it, fix it right.....it's not that hard and then will work like it was intended. I'm tired about hearing how a "tie-wrap" fixed the problem.
If you can't afford to do it right, or don't have the ability to do it yourself, then sell the car to someone who can.

 

So far my car is all original with out PO mods (except for a new radio.) I guess I don't want to start making irreversible changes now. Jay's mod seems like it would be a good compromise. I could put a T into the black line feeding the vacuum manifold and plug the blue line into that after fixing the re circulation flap actuator.

I have read all posting I can find on the HVAC vacuum system, including Wally's white paper and Tony's flap overhaul treatise. I still don't know where the flap actuator is. Do I have to go in through the top by removing the blower motor? If I start digging in from that direction will it become obvious what I need to do?

 

You have to remember that even if you have all the vacuum lines working perfectly, it's going to have air leaks through the flaps that open and close. It's a design flaw, period. Here in Miami, it's 75 degrees in the winter, so the heater is never used.

You can put it back to "factory new" and sweat, or do the mods and stay cooooool. It's YOUR car.

Don't feel bad about doing some mods to your car. These cars are not worth 100K, they are cheap fun cars. There is nothing wrong with doing some mods that will make your car more enjoyable(CD players,mufflers,seats,rims,etc).

And just think, you will have new car cooling in your old 928.

 

As usual, Wally is right.

I find it very rare to encounter a PO or aftermarket repair that actually improves something Porsche originally designed. Most often, it screws things up. As a result, I don't complain about Porsche, but wind up complaining about the PO or the repair shop. :^( YMMV.

Wally has written extensively on the operation of the HVAC system, and how to repair it. You cannot go wrong reading his recommended procedures. Even if you hire someone to do the repairs, at least you'll have a pretty good clue of: how the system is supposed to work, what needs to be fixed, the time it takes, and a good idea of the overall cost. Naturally, if you know all this, you'll probably do the job yourself - save a bundle, and have the rewarding feeling of having accomplished what seems to be an enormous task. YMMV.

 

The blower motor / re-circulation box is a sandwich....no better words to describe it. You need to remove both....one from inside the car, one from outside, to effectively get to the actuator. It is not hard to do, but a little time consuming. I think in Jay's instance his actuator was fine(held vacuum), but he just wanted to have re-circulated air all the time without climate control intervention, hence the "override" vacuum line. If your actuator does NOT hold vacuum, you either need to replace it, or cap off the blue line somewhere so the vacuum leak does not affect the other portions of the system, however all A/C operations will be with outside air only.....not the best when it comes to getting cold temps out of the A/C.
Check out this link for replacement help.

<a href="http://www.nichols.nu/tip506.htm" target="_blank">http://www.nichols.nu/tip506.htm</a>

 

Most of the owners that say the A/C system on a 928 is a design flaw, or never works right, has NEVER experienced a correctly functioning one.....PERIOD. On my third 928 now, and with each one I have gone through and fixed a few problems correctly and have been rewarded with
A/C systems that are colder then most new cars from the factory, they will freeze your A$$ off when done right!

 

Let me be perfectly clear - all of my vacuum pods work fine wioth no vacuum leaks anywhere in my car. I felt the need to provide continuous recirc as I have a black/black/black car. The recirc feature associated with the HVAC system has just been made a temporary-permanent feature by the addition of the extra vacuum feed tot he recirc pod.

 

It' true that a perfectly running AC system cools good. That is, in places outside Miami and other hot areas. This AC system is just not made for hot weather climate. I have had countless 928s and 911s(I buy and sell). They are all the same. There is an entire industry down here on upgrading AC systems(Everything from Ferraris to Porsches). Again, I speak from first hand experiences.

I personally would not do these mods if I lived somewhere outside of CA or FL. That's because the stock system should be able to keep up. But when it gets to 110+ and the heat index at 120+ , even a brand new Mercedes has trouble cooling it's cabin......