1997 geo prizm a/c recharge

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Jan 28, 2006
Scottsdale Arizona
Not getting any response in the other forum so I'll try something closer to home:p

1997 geo prizm a/c recharge
1997 Howdy
My friend wants to recharge his a/c, can you get a recharge kit from napa/kragen? I have never had to do this but would think that there are kits.
Is it easy to check the system for leaks? Anything else I need to know?
I would consider renting a manifold gauge set to see what the low and high side pressures are. Do a Google search on R134a pressure/ambient temperature to see what the pressures should be given the outside temperature at the time of testing (or better yet maybe he has a service manual). The refill kits sometimes have a tiny high pressure gauge on them, but I'm not sure they would be very accurate.

Refrigerant can be added until the pressures are in spec, but this is not the best approach because you really don't know how much R134a and PAG oil is in the system based solely on pressure. There is a risk over over-filling, which can reduce A/C performance and cause compressor damage. Best approach is to have the system evacuated at a local shop and then refill with the proper amount of R134a and oil.

If you do decide just to top off the system, I would at least get the cans that have a combination of R134a and oil. Take some before and after vent temperatures to see if it helped. My vague memory tells me with R134a you can probaly expect a 30 degree drop from ambient temp to vent temperature.
Paging Rex in 3....2....1....

Resident mudder down here in Tucson can help ya with any and all A/C questions, as thats his bread and butter.


Here's my opinion, fwiw: If you want it done correctly, take it to a shop that can recover the refrigerant that's in it, so you know if it's low or not. If it is low, there's a leak somewhere. They can charge it with the correct amount and add dye, to pinpoint the leak. This should cost well under $100.

That said, one of the recharge kits from your local parts store will probably work-don't trust the gauge, they're pretty inaccurate. With this method, it's pretty much a guessing game as to the correct charge level. Don't be tempted to add more and more refrigerant once it's blowing cold.
Using a pressure chart on a car is kind of iffy. The problem is depending RPM of the engine the pressures change. Different in a fixed piece of equipment that a motor is always at the same RPM. I remember a site glass in the liquid reciever. Never owned a car that had R144A that I had to charge. Most were the older R12 and those always had a site glass. I would run it at a fast idle 1,100 RPM or better and just charge it enough to clear the bubbles in the site glass. Watch if for a while to make sure it stayed clear. But stop once the bubbles clear to make sure you don't over charge it. Best way is to evacuated. Then watch and see if it will hold a vacuum. If it holds the system is probably pretty tight. Weight in a new charge to factory specs. That info a lot of times is on the hood/fenders/firewall.
In my limited 134a experience, gauges are a good tool to see pressures, but pretty much worthless for determining correct charge amount. 134a is more volatile (expands more with temp) so, airflow across the condenser, ambient temp, etc, affect pressure more. IMHO, the only way to correctly charge it is start with a vacuum and fill to weight/volume spec. I always under charge by several ounces, then sneak up on full charge an ounce at a time, using vent temp as the indicator for best charge. In my experience, the best charge for AZ is often slightly less than published spec.

To just top off, would use the same method. Add a bit, let it run/stabilize, check vent temp, add a little more, repeat until you get good vent temp. It likely wont be "correct" but should work. The most common mistake is over charging, most systems preform better slightly undercharged. Another mistake is having too much oil/dye/leak stop/etc, junk in the system, I look for pure freon without the "extras". If oil, dye, etc, is needed, I add them separately.

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