Strega(UK)

Hi guys, I have just rebuilt my a/c system with a new condensor and evaporater unit plus overhauled pretty much the entire heater box and had it gassed up. Problem is, it is useless!!

Is there anyway of upgrading this system to work half as good as a modern car or am I just stuck with it as is??

TIA

springer3

My AC does OK in Atlanta where it gets pretty hot and humid. I suspect your's is not at 100%. Is it as good as a modern car? Close, but not quite. It is in a different class from any earlier German car.

Metal Guru

My untouched A/C gets cold enough that I have to turn it down.
Something else must be in play here.
Are you using R 12 or R 134a?
Which brand evaporator did you install?

jneteler

I am happy enough with my AC here in tropical Malaysia. It is pretty much no go item if inop.

Assuming you have Adrian's book go to page 88. There are some graphs where you can compare ambient to center vent temperature for both types of refrigerant gases.

The other things I would check are:
1.) Setting the CCU temperature to minimum level (Don't ask how I know this.)
2.) Checking proper actuation of the servos that mix the hot and cold to get the set temperature.
3.) Check your base assumption that everything was together properly again.

Regards,

JNeteler

Strega(UK)

Ok, thanks so far, here is a few answers. No idea what gas they used, any idea how I would know?
The evaporator was ordered on my behalf so no idea what make, the box did say it was made for Porsche though.
Unfortunately I do not have Adrian's book, but I run the a/c in all configurations hot, cold, screen and floor, also with recirc on and off and everything actautes as it should but blows just cool not cold air out.
My car started off life in HongKong so I would imagine it worked well enough once, I just can not see why it is so poor now?

mr pg

R12 is not allowed here in the UK, so would surprised if it's that. It's never going to work as well as a modern car either. Yet another area that has moved on. Mine is cool, but effective.

DarrylH

You may have to go through step by step and make sure every subsystem is working. When it's working (mine isn't at the moment) the system is good enough for our 30 degree plus, high humidity days.

There's a good start to help work through it in the 993 forum, here. Best of luck.

Strega(UK)

Thanks Darryl, excellent info in there.

Metal Guru

R12 isn't allowed anywhere but there's still stashes of it.
I had several old cans that I gave to my wrench to charge my system up, which saved me a bundle.
When I need a new evaporator I'll get a Griffiths unit and switch to R 134a.

911URGE

My A/C system is all original and I had a similar issue in that my A/C would not get very cold even after an R12 top off. My vent temps were above Porsche specs. What fixed it for me was a mention of replacing the expansion valve in Adrians book. Once that was done the system came right down into spec with cold vent temps.

If my car sits out in the SoCal 90-100+ degree sun it may take a little while but it does get comfortable after 10-15 min of driving.

Ruairidh

I had my system changed to R134a perhaps two summers ago. A local non-specialist did it for less than $500 and it has enabled me to - once again - drive my car in the heat of Dallas summers. The system is never going to be as good as, say, my Lexus daily driver but like Stephen says, gets comfy after 5-15mins. And my car is an allblack interior.

Strega(UK)

I used the original expansion valve as it looked like ok to me, are these things prone to failure? Are there any outward signs of a malfunctioning valve?

Computamedic

Does anyone here have the correct refill data for the 964 a/c when using R134a?? The data I have suggests 660 grams of R134a and 19ml of PAG46 oil after a full evacuate. Any better offers??

Regards

Dave

dfinnegan

The Factory Shop Manual indicates on pg 87-28 of Vol 6:

As of MY '93
Refrigerant charge 840 g refrigerant R 134a
Refrigerant oil in compressor 140 +/- 20 c.c. ND 8

Computamedic

Thanks Dave, that's exactly what I was after.

Dave