charging A/C

[dgie]

Question I have a 1972 satellite with what I figure would be essetially the same A/C setup as most Mopars of the era. we charged the A/C with Freeze 12 this weekend, but am not sure if it is charged too high. The high side came out around 225 and the low side came out around 30 psi. We charged from the low side does anyone have any idea if this sounds too high. Not sure if I should let some freon out.

[is_it_EVER_done?]

I have no idea if freeze-12 should have that much pressure differential, only the manufacturer can tell you what the proper low/high pressures should be, but I suspect that you didn't evacuate your system prior to charging because an opened R-12 system that wasn't vacuumed will show such large differentials, but I can't comment on the freeze stuff as Ive never used it.

Is there really that much cost difference between R-12 and the freeze stuff?

[dgie]

The system was evacuated and held vacuum for 2 hours with no loss prior to charging. The cost of a can of Freeze 12 is $8 and the cost of a can of R12 providing you have a license to purchase it is around $35 a can. This times 3 cans well you do the math..... Anyways Is there anyone out there that knows anything about A/C systems in a car please chime in also I am looking for possible answers.

[John_Kunkel]

Freeze-12 is a blend of two refrigerants, it's 80% R-134a and 20% R-142b. Because of the high concentration of R-134 it should be charged at about 10% less than the R-12 system would normally be charged with. B bodies of that era usually use 40 oz. of R-12, so 36 oz. of Freeze-12 would be in the ballpark. Charging by weight is the best method.

The 225/30 gauge pressures don't seem out of the ordinary, what was the ambient temperature when those gauge readings were taken?

Regardless of what the sales literature claims, the mineral oil originally used in the R-12 system will not properly circulate with the Freeze-12 blend; don't be surprised if the compressor fails prematurely.

[dgie]

As far as the oil, we did not charge it with oil, so I do not know what kind of oil is in there prior, however since there was a charge and I feared overcharging with oil, we left it alone.  Also my belts I have noticed seem to be flopping when the system is on and when turned off they look normal. The load of the compresser seems to be causing this. I switched to Gates belts and there was no changethey still flop and at the same time are tight, Is this normal for B bodies and most Mopars with this setup?

[blue69]

Someone told me the belts from the dodge dealer have the least flop. It looked pretty good when he ran it. Make sure you get a matched set when buying a/c belts. I'm using dayco top cog belts, and they have some flop but I have yet to have one come loose. When I redid the a/c I replaced the drier, installed green o-rings, replaced the oil with pag oil, and vacuumed the system for 2-3 hours. It seems to be running great with straight r-134a. Its been over 4 months with no leaks or lose of performance.

[John_Kunkel]

The belt flop is a common phenomenon, there is just too much unsupported span between the compressor and the alternator; later installations have an idler pulley to alleviate some of the flop.