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Okay, this is on a 92 with the late model GM style air conditioning that uses an accumulator on the firewall rather than a receiver/dryer. On short trips the AC works great and will freeze you out of the car if you let it. On the other hand, if you are at freeway speeds in 90 degree weather for 45 minutes to an hour, the air flow coming from the side dash vents drops markedly and the flow from the center dash vents all but quits. You can still feel cold air coming out but not much. Once this condition occurs, if you turn off the AC for 10 or so minutes, the air flow gradually returns to full strength and it is still cool for most of that time. Once the air flow has returned, turning the AC back on will freeze you out of the car for roughly 45 minutes until the problem repeats.
This tells me that the evaporator coil is icing up and blocking the incoming air. Now for the real question since this system controls temperature based on high system pressure rather than evaporator temp/expansion valve, does this simply mean that the pressures are low due to an undercharging of refrigerant and resulting in the frozen up evaporator? Note, the system was converted with the Volvo conversion kit and a new compressor 3+ years ago to R134A after a full system flush.
Just looking for a confirmation of my stacked up assumptions before I climb under the car to hook up the high pressure service line to the port, low pressure port is easy right by the accumulator up to.
Thanks in advance!
jorrell
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92 245 287K miles, IPD'd to the hilt, 06 XC70, 00 Eclipse custom Turbo setup...currently taking names and kicking reputations!
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