I have heard that you are not supposed to put the R134 coolant in when it has not been coverted from the a12, is this true? Has anyone just tried to put the coolant in? Just asking because I just installed a new compressor in it, but the previous owner had never used the A/C (about 2 years)
Thanks guys

Its true, you need to have the R12 FREON recovered properly before converting to R134A, especially if its been sitting for 2 years.

To have the warrenty valid you need to put in a new dryer/ receiver. Then you can put in R134.

The the change was made from R12 to R134 there was talk about not being able to mix the 2 refrigerants but I have found that to be not true.

When you changed the compressor you lost all the refrigerant charge so the recovery part is a non issue.

Find out what the factory charge is and put the exact amount back in, more is not better.

Refrigerant being bad for the ozone is one of the biggest lies Al Gore ever pulled off,it's heavier than air,
now it's the CO2 lie.
Remember he tried to take credit of "Inventing the Internet"

You will need to pick up a gauge to measure how much R134 you put into the system. R134 runs at a higher pressure than R12, so you use about 20% less of the R134.

From what I understand you will get better cooling when using an R134 condenser and not the R12. I changed my '90 over to R134 in '98, and ran it for about 7yrs. At the time I made the switch R134 condensers weren't that easy to come buy, now 11yrs later you should be able to get one relatively cheap from a wrecking yard. IME w/R134 in an R12 system wasn't a good one. On Days over 95* it was useless, and at most ot would only cool the cab off to the mid '80's. In '05 I switched over to Maxi-Frig vs R12 and haven't had any complaints since. At the time I made the switch, my R12 comp was making a pretty bad noise on start-up, but has worked fine(no noise w/the Maxifrig). The one downside of Maxifrig propane based refrigerant, which tends to scare people away from using it.

Refrigerant in a system needs to be at a certain level.
If you are converting to R134 then an expantion valve may be needed, but not always.

To much refrigerant and you will run high head pressures.
To low of a charge and the compressor short cycles.

I just did a friends 89 pickup which I believe was a R-12 system. No problems at all Filled it until the sight glass on the receiver was clear and called it good.

Systems with receivers are more forgiving than ones with out.

By the way you charge a system by the weight of the freon.
A system that takes 3 1/2 pounds will take 3 16oz cans and a half of a 12oz can.

I was just trying to get around paying over a hundred bucks for the mechanic to put R12 in it, if it will potenitally leak out following next year. I don't mind paying $30 a year to put the r134 in each year. Thanks for the replys I might comb through the junk yards and find a new expansion vavle. Im not as worried about the dryer because It is a compressor from the junk yard.

When I retrofitted my system I followed the directions that came w/the kit, and used 80% of the 3.5lbs. However w/the Maxi-frig it was the same amount as w/the R12.

You could take the dryer and heat it to 125 degrees,purge it with refrigerant and it will work almost as good as new.

This could be a universal fix.

The receiver inlet simply empties into the cylinder.
The outlet is connected to a tube that goes down the cylinder, usually 3/4 of the way and picks up liquid from the bottom of the cylinder.
This way you pick up liquid with out gas bubbles and this is feed to the expansion valve.
Expansion valves do not like gas bubbles it makes the operate erratically.
There is usually a sight glass on the out side of the receiver. When the bubbles go away the receiver is full and the system is balanced.
Under filled and the system "Hunts", meaning the valve opens to far and then stays closed for to long and the evaporator is never filled efficiently.

As far as Maxi-Frig, I've never heard of it.
But I do have experience with propane refrigerant.

The cryogenic units in hospitals use pure propane as a refrigerant. But they use one unit piggy-backed to cool the cryogenic unit. And in the early years of refrigeration propane was used as a refrigerant, but from what I understand some leaks were disaster our.
But I don't believe in a automobile that it would be much of a problem. I'd like to see the pressure chart for Maxi-Frig

The info on their site Maxi-frig is the same info that came with the refrigerant. Of course as with any company claim you have to be skeptical of the claims. In my experience it seems to do as claimed.

I am not concerned w/it being propane based either, I don't smoke, and the cab isn't air tight, so not likely to blow myself up or asphyxiate myself while driving.