recharging AC

[Bullet Bob]

I just went through my AC system, replaced the hoses, condensers, evaporator, etc... I have a 2-stage scientific vacuum pump and I was curious how difficult it would be to recharge the refrigerant myself. Like I said, I only have a pump so I would need to get fittings, etc... and I don't know where to start. I figure it will cost a few hundred $ to have a shop do it so if the tools can be bought for that I would be satisfied as I could service my cars' ac going forward.

Thanks,
Bob

[Pazuzu]

Getting the freon (I assume you're sticking with R12) is the only hard part. You can absolutely pump down, test, and charge your own system. Have a t connection on each side with ball valves...AC system on one side, vacuum on another, R-12 on the third. Pump down the system as low as it'll go for about 30 minutes, seal the system for a day and check for leaks, backfill with r-12. Getting the various parameters (refill pressure) should be easy.

[scottrx7tt]

i use freeze 12, it is an approved r-12 replacement. It costs about $8 a can, and cools just as good as r-12

[Bullet Bob]

where would I get the fitting that interfaces with my car's compressor fitting? What kind of fitting is it?

[Jim Sims]

To correctly recharge you need to ensure you have enough refrigeration oil of the correct type installed in the system; oil must match the intended refrigerant or use one of the new universal oils. Although with R-12, one could use the sight glass method (if the car still has one - usually at the receiver/drier) to recharge a refrigeration harness/gage set calibrated for the refrigerant and with the correct end fittings is by far preferable (a reasonable quality harness is around $100) - essential if you will be recharging with R-134a. If you haven't done this before, obtain some experienced help familiar with a 911. You can damage your system and/or severely injure yourself if you make an error (like charging to the high pressure side). Always do this job outside and wear safety goggles. Do a search, there is plenty of 911 A/C information on this board.

[scottb]

Ah, it must be spring...when the minds of young men turn to -- AIR CONDITIONING THE PORSCHE!

[janz]

You didn't mention changing out your reciever drier, should be located behind front drivers side tire and is a necessary change out. Also make sure you change out all the "O" rings throughout the whole system. Was the system open to the elements or did it just stop working. Also each component you change out has a charge of oil in it, there is a chart somewhere. You can just measure the amount in a measuring cup and pour it into that part you changed if it did not come already filled with the proper amount of oil. The freeze 12 works great, at least it did for me but you need their special filler valve to attach it to a set of guages (which you should have for checking vacuum and charging anyway) their valve adapter is like $30. If your compressor is good and there are no leaks or blockages in the system your good to go. Should only cost you another $150. for the freeze 12 (gives you 2.5 complete fills) , reciever drier, oil and adapter. Go for it you went this far.

[Rrrockhound]

Originally Posted by janz

Was the system open to the elements or did it just stop working.

What does it mean if the system has been open to the elements?

[janz]

were the hoses off or ruptured, in other words was air and humidity allowed to get into the system? Oil leak out? Metal parts rusted inside the system?

[RSTarga]

If you've changed hoses etc. your system has definitely been open. You need a new receiver drier before proceeding. If you change refrigerants you may need a different expansion valve.

[Hester]

My Porsche doesn't have A/C but...

I just went through the A/C system in my station car (the A/C suddenly stopped working after twelve years). I replaced the expansion valve, the drier, and the compressor. I flushed out the hoses and the heat exchangers as best I could, oiled up the compressor, replaced every O-ring I encountered, and vacuumed and charged the system. I used a set of gauges and a vacuum that I bought from from harbor freight. R134a was the refrigerant.

My wife thinks I'm nuts because "there are people who do that for a living" but it is very satisfying to have 40 degrees blowing out of the vents when you did the work yourself.

[T77911S]

you never said if you were going to use 134 or R12. R12 fittings look like large schreder valves. 134 has a quick disconnect but the hoses have these squared off threads, dont know how to explain them. i have an old vacuum pump so i had to find an adapter (looked in 2 cities before i found one) to adapt the Vac Pump to the 134 gauges. i think they make screw on fittings to convert R12 fittings to 134.
check with polarbearinc.com. he is a very nice guy and will help you over the phone.
R12 is all over Ebay, well it was last year. i was going to buy a 20lb jug for $225. you can get a can for about $20. i would think with more people going to 134, the R12 will come down.
if a can of R12 substitute says FLAMABLE on it, DO NOT USE IT!

[Bullet Bob]

I bought the entire setup from Rennair and it included a different style of receiver dryer (Pro cooler), so other than the decklid condenser and the compressor (replaced last year) everything is new. I could go either way as far as refrigerants are concerned. What would you recommend?

The system was closed until last weekend when I started replacing components. I am not complete with the installation but all hose ends that aren't connected are capped.

[janz]

If you istalled a new receiver drier then your good to go. Vacuum it down should get close to 30, let the vacuum run overnight to boil all the moisture and some contaminents out of the system then cap it and let it sit for 24 hours and see if the you loose any vacuum, if you do you still have something leaking. If no leaks hook up a can of refrigerant to the hoses and let the vacuum suck it into the system, putting the can in warm water will help push it into the system. If it takes the whole can close the system and try to get another can in it will probably only take a half can and then tou can start it up and turn on the AC to get the compressor pumping and that will suck in the rest of the can. Keep adding until you reach the amount of ounces your system requires and you should have cold air.

[Hugh R]

Ok, yeah, I looked but here is my specific question. I'm only getting about 50 degrees at my vents, it's about 72 in my garage and my gauges are reading 35-40 on the low side and 100 on the high side. A page from ACKits says I should expect the following lower vent temps with lower low side pressures, like 16-29 PSI. So should I be adding more R-134a, or taking some out? The R/D is newer, barrier hoses, rebuilt Seiko condensor, and the correct oil for R-134a.

I have deck lid, L/R wheel well condensor with fan, and front condensor with fans.

[JFairman]

Does the low side drop in pressure when you rev the engine?
High side should be higher with that high a pressure on the suction side if the compressor is good.
Hard to say without more info... could be your compressor isn't up to making more pressure, bad manifold gauges or improper use of them, is the engine lid down while charging? or maybe ice is forming in the expansion valve or somewhere else from moisture in the system.

Is the front condensor warm or cold?

What is the static pressure of the system and ambient air temperature with the engine off after it has cooled off and equalized overnight.

[Hugh R]

Yes, low side drops about 10 psi,
Compressor is good, rebuilt last summer,
gauges seem to work, only go on one way, can't reverse them have high and low side R134a charging valves,
deck lid closed,
front condensor is slightly warm,
I can let it sit over night, and read the pressures, after sitting an hour, the gauges read 75 and 75 with red and blue valves both open and engine not running.

[JFairman]

R134 pressures change more than R12 with ambient air temps. What is the air temp where you are when you have 75psi static pressure.
Here in Florida when it's 90 out both my cars with R134 are around 95psi static psi... can't remember exactly because I've forgotten since last summer.
It's usually a bit cooler where you are so that won't correlate for you.

Maybe your expansion valve's orifice is too big or out of adjustment.

I would try adding more R134 seeing as your high side is low. It should be up around 225 depending on ambient temp if the low side is around 35.
Here is a chart, http://www.ackits.com/aacf/ptchart.cfm
You can always let some out if that isn't it. It even sweeps the system of moisture a little bit doing that.

[RSTarga]

I would have stayed with r12. r134 requires very efficient condensor and evaporator. Everything would have had to be changed. I think the expansion valve is calibrated differently also.

[Tim Hancock]

FWIW, DIY 134 conversion in SC complete!