Dealer A/C- HELP

[fireguywtc]

Sounds like you low side pressure is fine to me, it should try and stay constant. The condenser may be an issue as I put a larger one on my truck and run R134 and it works great, I can get down to about 42* vent temp on a 95* day. It cools the cab nicely. The hoses you have wont leak the 134 any more then anything else.

One thing you can try while you have everything to check the condenser is run water over it while running the AC, if you notice a large dip in high side pressure and you AC cooling a lot more then it is likely working inefficiently. Really the right way of rehabbing an old AC system is getting a new condenser, replacing all of the O-rings to stop the leaks, and flushing the system. Then add the correct amount of oil and refrigerant so you know you are good.

[ploeger_miles]

I will try the water hose idea. I hadn't thought of that. Maybe I will learn something from that test. I called Maxi-frig and they say that their refrigerant is supposed to be 30-40% colder than R12 or R134A. They say that they have never had a complaint about it not being cold enough. I take this with a little bit of a grain of salt because they are trying to sell it, but I think there is some truth in it. I think I will probably just take it apart and inspect the expansion valve and see if I can find anything wrong. Then probably put new seals in the compressor, flush system, new oil, new drier, vac down and check for leaks then recharge.

[1972hiboy]

So it might have been stupid but I charged my A/C with the Maxi-Frig hdyrocarbon refrigerant that my local auto parts store sells. Yes I know its flammable bla bla bla. It is supposed to be compatible with both R12 and R134A. Since my system was essentially empty, I figured I didn't have much to lose. The A/C works now but it is not as cold as it should be. The coldest vent temps that I can get are about 60 when it is 90 outside. Since this was a dealer installed A/C to my knowledge there is no label anywhere that says the exact fill amount for the system. So I was strictly using the pressure readings and the sight glass to fill the system. Is there any other better way to charge it if you don't now the exact fill amount? Anyways I think my expansion valve is either stuck or is plugged. I put three cans of the Maxi-Frig in and the sight glass was clear. The low side pressure was about 30 PSI but the high side pressure was about 250-260 psi. That seemed a little high to me. Could the expansion valve be causing my trouble or should I look somewhere else?

I may have missed something but figure id throw it out there. You didnt acually vac out the system? It was near flatlined on pressure and you just hooked the bottle up and shot some freon in there? If thats the case then thats probably why the system isnt cooling. You typically pull a vacuum on the a/c system to about 30 inches of water. Then charge the system. the vacuum draws in freon until its ambient. My guess would be your system isnt operating with the charge of freon its designed to. If the system had no pressure when you started I would think it sprung a leak and leaked down. whatever was in there prob wasnt freon but just air.

[ploeger_miles]

Actually- Maxi-frig says with their refrigerant to NOT pull a vacuum. It is different than the normal R12 and R134A and they say it works better if you do not pull a vacuum. I didn't have a vacuum pump and I wanted to know weather or not it would even function, so yes I just shot in some gas to see what it would do. I would definitely agree that it has to have a leak of some sorts or it would not have been basically empty. The thing is that this truck has been sitting a long time and I have no idea how many years or DECADES it might have been since the last time this thing was charged or even used. So unfortunately I also have no idea how fast the leak might be. There was slight pressure in the system. If you pushed on the valve core some gas would spit out. It was just very little and was not enough to register on the guage.

[1972hiboy]

well slight pressure is better then nothing. sounds like it might have kept the system clean at least. Ive never come accross max-frig before so I had to investigate a little. I called them directy. the lady said to pull a vacuum then release it before installing their product. What?? why bother vacuuming it? It is sapposed to do with its thermal expansion being more of r134a and r12. She did say it didnt cool down as fast as r134a and r12 and that I needed to be patient with it. ( I was posing as a repair shop dealing with a customer vehicle). When I looked at their technical page it said this....

How is Maxi-Frig Installed?
There are no new procedures to learn! The same gauges are used, and refrigeration systems are charged in the same manner used with the refrigerant being replaced. Maxi-Frig is completely compatible with the synthetic oil used with HFC-134a and the organic oils in CFC-12 systems. No flushing or oil changes are required.

If I bought this product I would assume this meant pulling a vacuum before charging. so thats kinda confusing. I hadnt thought about cross contaminating via a/c recovery machine at local shop. But take a look at their pressure chart for the the maxi stuff vs temp. with the fridgerant you have their chart claims say if you charged the system in 72'f temp your low side pressure should be 72lbs. 30lbs may not be enough. try pumping some more in there.

[ploeger_miles]

Yea I wish I knew the history of the system. I also called Maxi-frig and drilled them with about 20 questions. All of them the lady was glad to answer and she knew all of the answers off the top of her head without having to check with anyone else. She seemed very knowledgeable about the product she was selling. I also asked her about the vacuuming thing. She said to vacuum it to remove the moisture then just equalize the pressure really quick. She said this should not be enough to contaminate the system but just enough to equalize the pressure. I do not plan on ever taking the truck to a commercial a/c shop as they would definitely not want to mix this with their R-12 in the recovery tank. If I ever did I would at least let them know about it first. Although it shouldn't be that big of a deal since it is claimed to be completely ozone safe and won't matter if I just dump it. I sure can't complain about the price of it. You can buy a whole case of 12 cans for like 55 bucks free shipping. Works out to be about 4.58 a can. That's way cheaper than 134a and WAY WAY cheaper than R12. I've decided to be the guinea pig and try it. I will definitely let you guys know how it works out in the long term. About the pressures- the lady I talked to said that the chart was for the high side pressures. Which these seemed really low to me for a high side pressure but also really high for a low side pressure. I tried one can at first, then a 2nd, then a 3rd. It put out the 60 degree semi-cold air after just one can but did not get any colder with the 2nd or 3rd. The low side pressures did not change at all between the 1st can and the last. I am afraid to put in anymore. One can is 5 oz. but is equivalent to 15oz. of R12 or 13.33 oz. of 134A. This would mean I have the equivalent of about 2.8 pounds of R12 in the system. I have no idea how many pounds it is supposed to take. Thanks all of you for your input.