Hey guys,
I am converting from r-12 to r-134a. Does anyone know the specs on the ac system? According to the manual I need to fill the system to 80 percent of system capacity. There is no data plate in the vehicle, and all I have is the haynes manual which does not get into it. What pressures have you guys filled it to?

Thanks Ivan

 

If your ac works leave it r12 it is colder and r12 price has dropped look on craigslist for cans.

 

I agree, unless you are rebuilding the system then I would leave it R12. It is colder. Other wise you can use your Ford dealer add on under dash unit if you change the expansion valve to a 134a unit. You will also need barrier hoses and a sanden compressor. If you go that route I would just take it to a shop to have it charged.

 

Actually the York recip compressors are quite capable of r-134a and in fact do so in commercial service. The antique one on your 60s mustang will just need up to date seals and gaskets. You do not have to use a Sanden compressor which looks all wrong on early mustangs to have working AC.

 

on my 70 with factory ac its tag said 1 & 3/4 lbs. r12. the thing is that if you live were temps dont get above 100 degrees youll be alright with 134. you need to know that if you have a small leak with r12 you will have a big leak with r134. also you really need to vacuum the system that way youll end up with less pressure when you fill it up. youll get a pressure gauge with the kit. just put your hand on the return hos and wait until it gets cold and watch the pressure. i did a conversion on my 70 and it worked ok, temps here are 100-125 degrees, AZ, so i finally did a complete r134 conversion, sanden 134 compressor, all new r134 hoses, high efficient condenser and new dryer. you can buy all these items today on line and they are a direct replacement fit for the old r12 stuff, no modification needed.

 

with the falling number of cars still using r12 the prices of r12 have stabilized and even fallen some. Reclaimed r12 is still readily available. I would not suggest conversion on an antique car unless full system restore is going on, IE if you are buying compressor, hoses, dryer etc anyway, you might consider r134, if you have a working r12 system, keep it r12. It will work better and the freon is not that expensive considering the system only uses 1.75 lbs.

 

First let me say that you must evac the system of all air and compressor oil. The oils are not compatible and air does not transfer heat as well as freon does.

I know you are supposed to fill the system with a specific amount of gas, but after the first year, that all goes out the window, so I fill based on pressure (high and low side). The pressure your system creates and should have varies based on the ambient temperature of the air being pulled through the condensing coil (air temp + 40*F). Generally, I set the gas so that on a 95* day the low side is no higher than 40-45psi and the high side is no higher than 225-250psi. Most charts show you freon temp verse pressure, which is totally no helpful, but those pressures I mention work pretty well for me. You need to check the pressures with the car at temperature and the A/C on max cold. If you have high high-side pressure and low low-side pressure, you have a restriction and flow issue.

 

Here is a pretty decent chart I found. The ranges are pretty broad, but will get you close.

http://www.ackits.com/aacf/ptchart.cfm

 

Thanks For the info!

 

I was not aware that the York would work with 134a.

Cowboy is right. The system needs to be flushed and evacuated.