Dash Air Conditioner R134 Volume?

[Rickf1985]

Would anyone have the charging spec for the P30 W/454 and R134? I need the volume specification. (ounces)
Basically this is a total refill from an open system.

[DaveVA78Chieftain]

Original system was R-12 so if not already converted to R-134 that will have to be done.

Because GM does not control interior setup of an RV, the P-30 service manual does not list quantities for P-30.   The G-Van model should be ball park though so:
Refrigerant - ~ 4lbs
525 Oil - 10oz.

Dave

[chip2lane]

I found the specs for my coach and it was 2lbs or 32 oz. Hope that helps. My dash system is a scs/frigette system

[Rickf1985]

Chip, My system is a factory GM system and I know it should be close to what Dave mentioned. I was actually thinking a little over three pounds myself. Mine has all 134 fittings on it and they are not conversion fittings so I am wondering if this was converted as a whole from a later unit. I had to open it up when I pulled the front off to replace the water pump and will have to do so again when I replace the radiator. I will probably do that before vacuuming and charging it. It was empty when I opened it so I am going to have to leak check it first anyway.

[DaveVA78Chieftain]

My thought pattern was G Series van is 3lbs 8oz.  RV is bigger (longer hose runs) so RV would be ~ 4lbs (ball park).

Dave

[Rickf1985]

I'll start at three and watch the gauges and temps.

[Lefty]

R134 should be filled 20% less than R12. Temp's at full charge should be about  40deg. less at the center vent than ambient temps with system on max cool. This varies with humidity. Also, be sure to adjust the clutch cycling switch. Unplug the switch, look inside the hole and there is a flat blade screw head. Turn it 1/4 turn clockwise, then plug the connector back up. this sets the switch to turn on & off at the higher pressures needed for R134 to cool properly. Number 1 reason people complain R134A doesn't cool as good as R12 is they haven't adjusted their switch to compensate for the difference in pressures.

[Rickf1985]

Good info, I have always been lucky I guess and the conversions I have done have all worked well. Do you have the pressures that should be in and out and the location of the switch for those who do not know? Beware, this is not a repair for a system that has stopped working. If you bump up the pressure too much you will damage the compressor.

[Lefty]

It depends on ambient temp, but from 70-80deg F low side should be around 20-30psi/ high side 115-200psi with a center vent temp of 35-50deg F
At 80-90 ambient, low side should be 20-40psi/high side 140-235psi with a vent temp of 45-60deg F

I usually aim for about the 30'ish range low side/ and 175-200 high side... When center vent temp is running 30-40 deg F less than ambient, it's about as good as it'll get.
The compressor is rarely a problem as far as setting the switch up is concerned... they are rated for 300psi min. The switch is usually located on the dryer, it looks like an oil pressure sending unit... round, screws in, has a rectangular plug, two wires. And I was backwards with the direction to turn the screw. It should be COUNTER-CLOCKWISE.
R134a is far more sensitive to over filling than R12...An overcharge can cause it to not cool well.

[legomybago]

Your talking about the low pressure switch Lefty? I didnt know you could do adjust them...Thats cool