There are many people who have ran r152a/computer duster for long term. I have been running it in my 91 for about a year and a half now with no problems.

 

similar is not the same as the same thing. these systems were designed for R-12. doing a 134-A conversion will not work as good unless you convert the whole system to work with 134-A. and that will cost big bucks. new compressor, new receiver drier, new condenser, new evaporator, new lines, new orifice tube.
even the freeze 12 "drop in" refrigerants use some 134-A.
i have also seen people use butane and propane based refrigerants, even though they are illegal.

 

We can sit here and argue all day but in the long run everyone has their own view point. I am not a fan of hacked R12 to R134a conversions. I personally think even less of a conversion to R152a. As long as I can get R12 at a reasonable price I'll use it.

Thanks to those who offered up an alternative...YMMV

 

I tried butane in my Bronco and it did work, but it's not for the average Joe. You gotta know what you are doing to get the charge right.

You can thank the government who took DuPont's money for the situation we are in with refrigerant. It used to be you could buy R12 for 50 cents a can in the 70s. It's no different than Philips paying to get incandescent bulbs outlawed on the canard that they are bad for the environment - just the other day I was in Home Depot and 100W incandescent bulbs (they are legal if made in the US to certain restrictions) are now $3 a pop. Thanks, Uncle Sam, you *****!

 

During the 90's I worked for a company as an engineer that was testing retrofits on Ford vehicles. The Ford F-150 is one of the easiest to retro fit to use R-134a. We did several trucks with differing engine sizes and all worked as well as the R-12 systems. You will have to change the accumulator, the orifice tube, and the oil in the system. Best way is to remove the compressor and drain all the oil from it you can and refill with a PAG( poly alkyl glycol) or PAB( poly alkyl benzene) based oil. Flush the condensor and evaporator with an approved flush media and reinstall compressor, new accumulator and orifice tube. When re- charging the refrigerant to use the newer R-134a the amount of charge will be approximately 80% by weight of the R-12 used. You will notice an increase is the discharge( high) side pressure of about 15 to 20 psig at idle. Low side pressures will remain fairly consistent with R-12 pressures ( 25-35 psig). You will only need to change hose connection seals with newer compatible materials if you opened them or they were leaking. Be careful with the oils. MINERAL OIL as used in the R-12 system is immiscible ( not mixable) with the newer PAG oils. When they do mix if any water is present,they form something akin to a fishing worm type gel that will require almost a total replacement of system.

 

That is exactly why I caution anyone contemplating doing this conversion, it has a serious pitfall. Some get lucky, others do not.