Heating and Ventilation

Have 1988 928 S4.  Has had 134a conversion.  Would like to be able to top off 134a as seems to have lost colling over time and last fill (full evac & fill) helped but now due for some added coolant.

Any tips on how to get to the low pressure valve?  I can clearly see it but seems almost impossible angle for access. 

When I slide the A/C Control Head lever all the way to the right Defroster position the Defroster sometimes comes on and stays on, sometimes comes on momentarily and quits and sometimes never comes on at all. Coming on and staying on seems to relate, again sometimes, to colder outside temperatures.  The blower works fine with all the rotary positions.  I have swapped relays but this did not seem to have any effect. Electrical problem, vacuum problem, something else? 

Model: 928 s4, Year:1987, Mileage:36000, Type of use:Street use only
my wife's 928 has been to the dealer on 3 separate occasions this summer for a/c repair. the car never holds the freon for more than a week or two and so far I have spent over $2500 on everything from fuel line cooler, valves, and a conversion. The car still does not have working a/c and I am at my wit's end. How can a Porsche dealer be unable to repair the a/c system? What are my options at this point? Would contacting Porsche help?

Vehicle Information: Year: 1993; Engine (size, modifications): 5.4 L; Total Mileage: 100,000; Transmission type: Autotomatic;

The air from the vents smells strange and I need to find the air intake vents to so I can add some disinfectant, or other spray to cure the odor. So can you tell me where the air intake is located, and any suggestions on disinfectant for the smell

Vehicle Information: Year: 1983; Engine (size, modifications): 4.7L; Total Mileage: 172000; Transmission type: Autotomatic;

The A/C seemed to work when I first bought the car in July of '07, but it worked only a few times. I didn't bother much with it over the summer, but now it is winter and I thought that I would have a look at it.I thought first that I should figure out if the system has been converted to R134. How would I determine this? Also, what would be my steps in diagnosing the problem(s) from there?

Vehicle Information: Year: 1984; Engine (size, modifications): none; Total Mileage: 98,000; Transmission type: Autotomatic;

During a test drive of a 1984 928S I noticed that a lot of heat was coming into the cabin of the car even though I had the a/c on and the outside temperature was only in the high 60 degree range. The heat was so excessive that I found that I had to have that a/c on at a fairly high level to keep the cabin from becoming uncomfortable hot. Any idea what the culprit might be what it might cost to have a 928 specialist fix this?

Vehicle Information: Year: 1987; Engine (size, modifications): V8; Total Mileage: 43,000; Transmission type: Autotomatic;

My air conditioning works great, but, when I turn it off and roll down the windows, the vents blow warm air. I like having my windows down, but it gets really hot inside the car. What is going on?

Vehicle Information: Year: 1988; Engine (size, modifications): 5.0; Total Mileage: 141000; Transmission type: Autotomatic;

Vehicle Information: Year: 1987; Engine (size, modifications): 5.0; Total Mileage: 87000; Transmission type: Manual;

Vehicle Information: Year: 1987; Engine (size, modifications): 5.0 liter; Total Mileage: 80000; Transmission type: Manual;