howdog928

Does someone know how much freon an '88 S4 takes at capacity?
I'm trying to price out R12 cost compared to R134 as my compressor has seized and I need to re-do the AC.

Thanks,
Howard

the flyin' scotsman

It depends on whether your car has rear a/c or not.

IIRC the capacities are listed in the HVAC section of the WSM.

dprantl

Off the top of my head, I know the R134a capacities:

Without rear A/C: 860g
With rear A/C: 1030g

The amount is approximately 15% higher for R12.

Dan
'91 928GT S/C 475hp/460lb.ft

928mac

It should be measured in lb/pounds.

most auto systems start around 1 and 3/4 pounds and to around 3.0

it should be marked on the dryer but it is best to look it up.
To much and you will break the compressor

Just remembered that mine has a sight glass so yours may as well.
if you see bubbles in the glass it needs more. (go slow 1/4 at a time)

SeanR

That's close enough, most all European cars are measured in oz . Oops.

rgs944

Timely question for me. Also, how much oil do you need to add for a completely empty system? One more thing, will local parts houses still have the oil for R-12?

dprantl

It should be measured in whatever units someone pleases. Porsche specifies it in grams. If you ask me, pounds and ounces is an idiotic and inaccurate way to measure mass.

Yes, most places should still be selling mineral oil, which is what you should use for R12 systems that have never had anything other than R12 in them.

Dan
'91 928GT S/C 475hp/460lb.ft

Vilhuer

Automatic GTS was converted to R134a in Germany by local dealer. Users manual has added sticker which state how much new style stuff should be used. Can't recall exact quantity but its clearly less than original R12. Something like 20% less. AFAIK all components are still same as before. Only seals were changed.

928mac

For the last 25+ that I have been doing ac work and the way GM and every north American car company has ever done it, it has been in Pounds. If I lived on the other side of the pond and they used Grams, then that is the way I would have learned.
But I Trained in Texas at LeTourneau and have 2 degrees up here. So ya everyone is idiotic.
You never just fill, you monitor pressure and temp, Dan.

jcorenman

dprantl

^^^
Well that's not measured in pounds, so it's no good, and probably why your transmission cooler is leaking coolant upwards



Dan
'91 928GT S/C 475hp/460lb.ft

MainePorsche

^^^
Yep.

howdog928

Good info guys, thank you.
BTW my rear A/C is capped off, so just the front to worry about.

I know this has come up many times before, but what are the downsides to converting over to R134?
What is the current consensus on R12 vs R134?

928mac

I think the biggest down side would be the cost of converting.
R134 dose not have as low a boiling point as R12 but with the higher pressure 134 is run at some seem to feel the cooling is close to the same.
In most vehicles I can get the 134/AC down to 38-40F at the center vent, it depends on the humidity and temp of the day.
Dichlorodifluoromethane (R-12) is harmful to the ozone and so has been banned in most places.

http://en.wikipedia.org/wiki/Dichlorodifluoromethane

.

.

griffiths

R12

1978-1979
R12, 950 grams or 33.5 ounces

1980 - June 1988
Revised Factory recommendation,

Single evaporator systems R12, 1050 grams or 37 ounces
Dual evaporator systems R12, 1200 grams or 42.3 ounces

July 1988 - 1992
Single evaporator systems R12, 950 grams or 37 ounces
Dual evaporator systems R12, 1150 grams or 40.5 ounces

*before you attempt to charge using refrigerant weights
stated above, always check in the engine compartment for
the factory R12 sticker, and verify the charge using an
R12 Pressures and Temperatures Chart

R134a

1978-1982
R134a, estimated 807 grams or 28.5 ounces

1983-1992
as per TB, 9501, 12/19/1995

Single evaporator systems R134a, 860 grams or 30 ounces
Dual evaporator systems R134a, 1030 grams or 36 ounces

1993 onward
Original Factory recommendation

Single evaporator systems R134a, 860 grams or 30 ounces
Dual evaporator systems R134a, 1050 grams or 37 ounces

*before you attempt to charge using refrigerant weights
stated above, always check in the engine compartment for
the factory R12 sticker, or an R134a retrofit sticker,
and verify the charge using an R134a Pressures and Temperatures Chart