usc944

Hi all -

I have an A/C question regarding 944s.
I have a 1987 944 NA.

I recharged my system by myself with R 134 and it was cold for a while...but then, it stopped working... The compressor doesn't spin, which means it's low on fluid...but so, when I put more fluid in, the compressor engages, but not much fluid goes in...

Is the low pressure side [where i'm suppossed to fill it] by the left strut?

I didn't get the system vaccummed of the r-12...it leaked out on its own... [prior to charging the r-134, i had replaced the compressor and condenser]

Help!!
Thanks =)

Tabor

Did you drain the old mineral oil out of your compressor and replace it with ester oil before charging it with the R134a? If not you probably fried your compressor (to my knowledge).

My understanding is that you really need to have the system evacuated. And it is very important to get the correct amount in.

More AC Info

Note: I have no first hand experience with AC. I only know what I have read, mostly one Griffith's site (see link above).

rfuerst

Yes the low pressure side fitting is near the left strut,on my 1987-944S it actually is on the compressor low pressure hose.It seems that you still have a leak so you need to figure out where and fix it.I agree that you should have the system evacuated,and this also will tell you if you have any leaks,basically they pull a vacumn on the system for aprox.15-30 minutes and see if it holds.One trick when filling the system is to put the can of refrigerant in a pot of hot water,this raises the temp. and pressure in the can and forces more refrigerant into the system.Remember that when converting from R12 to R134A you only fill aprox. 80-85% of what it took for R12.Sorry for the long answer.

Mark944na86

As well as replacing the refrigerant going r12->r134a, you have to replace the oil (ester based rather than the mineral oil used with r12), and the drier (which is a bit like an oil filter for the system, as I understand it; it traps enough of the old system fluids that leaving it in would contaminate the r134a and r134a-compatible oil.)

Also, the seals on the compressor may have to be replaced to be r134a compatible. I assume since you have a new compressor put in, this would not be an issue.

My car had a quick-n-dirty r134 conversion done (I found out when the compressor seals failed < 2 months later). The mechanic definitely hadn't replaced the drier, I strongly suspect had neglected to do the seals, and hadn't even put in the conversion stickers under the hood detailing what the conversion specs were (refrigerant type, quantities, pressures etc.). The entire conversion had to be redone effectively to do it right, which was costly. So even getting it done professionally is no guarantee it's been done properly, unfortunately, unless you know what to look for and the right questions to ask. Definitely have a look at the Griffiths site that Tabor has provided a link to above -- very illuminating. Good luck.

-Mark 86 944 NA

usc944

wow.
thanks for the replies!!

mm... and some latest development.

my vents now blow hot air out...even without the a/c turned on... does this have something to do with the a/c system?
maybe I did fry something...any ideas?

thanks...
[i'm in a lot of trouble huh?]

Greg Hammond

NO NO NO NO NO!

The low-pressure charging port is UNDERNEATH the car, directly attached to the compressor. There are two "tubes" leading up to the evaporator. The "thinner" of the two tubes is the high-pressure line, and has the high-pressure test port right next to the driver's side strut tower. If you hook up an R134a bottle to the high-pressure port, it will NOT fill your system, and does run a very good risk of exploding the R134a cannister due to the high (250+ PSI) operating pressure of a fully-charged system.

Now! You -can- retrofit your system without changing the drier and removing the R12 mineral oil, but you ABSOLUTELY MUST charge your system with approximately 8 ounces of R134a compatible POL (polyol ester) oil. If you neglect to charge with the R134a oil, you most definitely will fry your compressor in a very short period of time.

Ya see, the oil in the A/C system actually "mixes" with the liquified refrigerant. R12 will not mix with R134a oil, and R134a won't mix with R12 oil. The oil is used to lubricate the compressor, and without it - you have a very bad situation.

The RIGHT retrofit involves purging whatever R12 is left in the system (there is no doubt "some" R12 left, probably 40-50 psi of static pressure worth). Then you vacuum the mineral oil out of the system using a recovery pump and filling the system with nitrogen to displace the oil and prevent moisture-containing air from entering the system. THEN, you fill with 12-24 ounce of R134a, then 8 ounces of R134a oil, then top off with R134a until your low-side and high-side pressures are optimal.

Simple, right? *grin*

Greg

rfuerst

Sorry for any confusion in my response,when I said near the left shock I did mean underneath the car,not the fitting up on top.The one on top is the high pressure side.

Robert Des Rosier

I talked to a guy at the AFB shop here in Del Rio, TX. He gave me directions to different stores in Acuna, Mexico (just across the border) where they sell r12 for about 6 dollars and charge a system with it for around 5. Aren't I lucky. Its too bad that smuggling it across the border is illegal or I could hook everybody up.
-Robert