Engine Size: 2.8
Refrigerant Type: r124a
Ambient Temp: 84
Pressure Low: 35
Pressure High: 290
Country of Origin: United States
Checking charge on this system added 1 can vent temp went up about 2 deg removed some charge temp went down about a degree. but then stopped.
1500 rpm ,max air, center vent temp 49-51 deg cabin temp at evap input 80-85
does this sound normal?
seems that low side high high side low. should orifice have been changed when system was converted?
Could compressor be weak. AM thinking about evacuating system and starting over since charge is unknown.
Low side sweats good all the way to the compressor so I think charge is ok but just cant seem to get low side down where I want it. No frost. The cycle switch is an r12 switch but the system isn't cycling today so I am not worried about that.
Thanks in advance
Forgot to add that the realitive humidity is 65% measured with a sling phsycrometer.
Edited: Sun April 04, 2010 at 9:24 PM by wildbillvette
Agreement with the idea of recovery and recharge. Knowing the correct amount of refrigerant within the system is a most important step for system diagnosis. As long as the system is open, why not completely flush the system to remove the possibility of excessive lubricant also.
The pressures for the system are border line, however, with a retro fit pressures actually become less meaningless than many expect.
Since the system is going to be open, change the accumulator and orifice tube also. Some recommend the use of the Ford orifice tube, however, bench testing has indicated a minimal change when this change is made. The system can and will work with the standard GM orifice.
Add back the correct amount of lubricant, 2-3 oz in the compressor and the remainder into the inlet side of the accumulator. If possible remove and drain the compressor and replenish the compressor lube as indicated above.
Evac the system and add refrigerant into the system. Try this, MAX AIR, HIGH BLOWER, ENGINE IDLE, DOORS OPEN. Add refrigerant into the system until the evap inlet and outlet are the same temp. This test should be conducted with a tool to measure surface temperature of the lines. Start with a 85-90% recharge of 134a to 12 specs. Also keep in mind with this formulation is the amount of refrigerant necessary to pre fill your manifold lines. Normally about 4 oz. Once this range is obtained, allow the system to operate for app 7-10 minutes, this allows the system to stabilize and then measure your temps. They should be equal or within 3-5 degrees of each other. If the outlet is warmer than the inlet by more than 8 degrees the system requires more refrigerant. If the inlet is warmer by more than 8 degrees, the system has an excessive amount of refrigerant or may have too much lubricant. Adjust accordingly. When ever a change is made in the amount of refrigerant the system should be allow to re stabilize prior to pressure/temp testing.
There seems to be nothing wrong with your compressor...it is working properly.
Considering the age of your vehicle, the retro fitting of a vehicle that was never designed to operate with the higher pressures of 134a, your system is operating very close to specifications. Have your tested the pressures/temps when the vehicle is moving. The added air flow should enhance condenser cooling and aid in the maximization of vent temp drop.
Also check the fan clutch on this vehicle. If over three years or 50k miles, replace the unit. Make sure the rad is cooling to OE specs.
Good luck with this retro.....the best policy would be go return the system to r12...it will perform much better.
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Thanks alot for your reply.
I considered the return to R12 I am just worried about continued availability. I have several other vehicles that could or do use r12. hasn't R -12 production stopped? If so do you think there is enough around to last? maybe with everyone converting the r12 will last longer.
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