glencase

These questions are concerning a 94 968 with the r134a a/c system
Assuming the a/c and vehicle are working correctly

1. what temp. is normal out of the vents
2. will the a/c compressor cycle or stay engaged
3. what high and low side pressures are normal at about 80 degrees

4.where should the temp guage on the dash read when driving with the a/c on with 80 degree temps

Thanks

glencase

Does someone have a manual with
Hi and Low side pressure specs or a page that they can scan in with a chart with respective pressures and ambient air temps. My a/c is not as cold as I think it should be even on a cloudy 80 degree day.

I've looked at the cans they sell at Trash Auto and it says that normal low side pressure depending on outside temp should be between 25 psi and 45 psi.

I want to top the system but don't want to blow any lines because of excess pressure.

Thanks,

ChrisJ951

134a is not as cold as the old freon. I was talking to a mechanic friend of mine, although works on Jap. cars he will replace my compressor because he has ashop and I trust him. Anyway, he said something about 134a not being as effective and his shop uses a safer varient of the R12 freon, which is about $25 a pound, enviroment safe and better cooling the 134a.

AndyK

I was converted to 134 last month, and my A/C is freezing!! 38 degrees on a 78 degree day! Yay!!

Tom R.

I had the 134 in my Red S2. it got pretty nipply in my car with the AC on, even on the hottest days. I recommend it.Wait, it is irrelevant. His car came with 134 from the factory. why would he want something else?

nickg

r12 is more like $75 a pound.ther is no "safer" equivelant to it. he is using Frig or freeze 12, both of which have there own set of problems
r134a systems are very close in terms of temp drop to r12. converting an older r12 system is not hard, you can get the kit at walmart, but there are things to consider.
1 you should drain the system of as much oil as possible and change the receiver drier then refill the system with Pag or ester oil(I use PAG)
2 you should charge the system with r134 to about 80% of the r12 charge as the 134 operates at higher pressures. you are looking for low side pressures to be as low as possible(this ensures maximum expansion at the evaporater)
944 porsches do not have barrier hoses s the refrigerant will permeate the hose and require recharging evey so often.(the 134 molecule is smaller than r12's) also, porsche does not use a cycling type compressor, it is either on or off.
3 you will need a vacumm pump to draw a vacumm on the system for a minimum time of an hour to boil off all the contained r12 not already purged(and don't open a charged system to atmoshpere..it is not a smart idea)
Most A/c systems will have ducts temps of between 36-42 degrees on a dry 80 degree day whenn working right. regardless of which refreigerant it has in it, most people who think it is not as good as r12 , overcharge the system and it isn't as cool that way. It is also normal however with this said to have a duct temp that is about 20-25 degrees less than ambient. My cab will pull 37 degrees and it is a converted system..it just needs to be recharged every year or 2...i can afford the $21 that cost me

AndyK

Hey Nick - My compressor cycles on, and off. What do you mean by non-cycling?

Also, how hard is it to top off the R134A--my mechanic said it would cost $140 to do it--and I'd rather go the $21 rout!!

Scuba Steve

Pretty sure he's got 134A from the factory. I'd say you want temperatures at the dash of 50 degrees at the absolute most, otherwise it'll start to feel pretty hot in there.

KuHL 951

Nickg about covered it all very well. I'll add that if your compressor isn't kicking off you are ,most likely just low on 134a and a recharge is required. If your compressor is coming on you aren't low enough to make the low refrigerant switch from preventing the compressor from working. I always use a digital thermometer with outside temp probe and watch the vent temp as I'm charging. I've noticed that as the temp drops it will reach a point where it stops dropping and sometimes will climb back up. If this happens shut down the charging valve immediately because you have put in too much 134a. Even with an AC manifold to monitor the LP/HP sides you will find that the values are all over the place when you are charging a hot car in a hot garage with no air flow over the condensor. Once I test drive the car the vent temps always drop at least another 8-15 deg. depending on the ambient temp outside. Your system should work fine if your 94 came with 134a as standard. If it's been coverted from R-12 then it's different story

KuHL 951

So if your system is 38 deg. why the second post? Is this for a different car?

nickg

a type of ac system. there is cycling (normally a domestic style that Gm and ford use) and non cycling. what it means it that on a cycling style, the cluctch kicks off and on as required by pressure switches in the system. Porsche is either on or off...it should not cycle unless you have low charge or freezing at the evaporator.
his 94 does have r134 standard btw...good system in that car

nickg

Andy, the $140 to convert isn't that bad a deal, I was reffering to the fact that I top it up every year or so and it usually costs about $21 to do that ( I have all the tools and gauges to do ac work whenever i need to..I still have 3 case of r12 too )

AndyK

No, I already converted. He would charge me an hour's labor ($100) plus about $40 for the extra R134a, should I bring it to him to recharge in a year or so! THAT seems very high to me!

nickg

getting hosed there...r134 is only $9 a can at walmart (and they are all made by dupont btw so branding is no concern) you can get a can that tops it up for like 20 and you won't need gauges with the top up(recharge) kits..the low side is on the compressor and that is where you charge at.

glencase

All good information and I appreciate it but no one has earned the Gold Star yet. I'm still looking for,

Hi and Low side pressure specs or a page that someone can scan in with a chart with respective pressures and ambient air temps from a shop manual.

And yes this is a factory 134 system on a 1994 968. I want to top it without over charging and blowing my lines, it has not been open to outside air so it doesn't need an evacuation, it just doesn't cool quite enough. The compressor is not cycling so I assume it is just a little bit low.

Thanks,