How much 134a
 

Hello all,

89 v2500

I converted to a sanden compressor and the install was straight forward. That said,, I feel the pressures are wrong for the temperature and not sure if more ounces is the answer..

I have 36 ounces in there now,, i feel that is more than with the r4, but then i undercharged the pancaked compressor to keep the high side pressure lower and it was bitter cold. The compressors o-ring would fail after a few years.


I have all the right tools, yellow jacket gauges, pulled a vac, no leaks etc. As of now, I have ~30/210 psi. The 30 PSI feels low compared to the return line and vent temp. When driving it just never gets cold. 60s out of the vent using my infrared. (feels warmer)

The orifice is from the original r12 to 124 conversion.. I did not change it for the sanden. Not sure if there is a difference

anyone do this conversion? How many ounces? Are my reading indicative of air in the system? I hae read 3.5 pound for r12 and 3.2 for 134.. Feels like a lot??

Thanks,
Chris

Re: How much 134a
 

I have always googled a pressure chart based on temperature then add or subtract refrigerant to meet the suggested pressures (high side & low side)

Re: How much 134a
 

Did you change out the drier and flush the system of all the old oil. been awhile since I've done a conversion but If I recall the 134 going in is supposed to 80% of the R12

Re: How much 134a
 

Depends on the OAT for your pressures. Pressure does seem a little low for the low side. Did you change the orifice tube when you did the swap? The chart on 4 season AC says 52 ozs of R12 for your truck. 75-80% of that for R134A. Keep in mind that if you changed your hoses (shorter or longer) that will affect you numbers somewhat.

Re: How much 134a
 

I was told the orfice has to be changed.so i changed mine (i think it was a pink color tube) ( color coded based on freon type) added 1 can of freon to a new system and I am good . My pressures are in the range of R134 replaced dryer with a factory dryer

Re: How much 134a
 

When i converted the pancake compressor from r12 to 134 i changed the orifice, accumulator, and flushed..

When i change from the R4 compressor (134) to the new sanden I changed the accumulator/dryer/hoses and flushed. (did not change the orifice again).

I guess i am undercharged at 36 ounces,, I read 51 ounces of 134 and if 4 seasons is correct at 52 ounce of r12 that would equate to ~42 ounces of 134.


I will continue to add and report back