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85' Ford LTD AC Woes - Low Discharge, High Suction

style86 on Tue September 29, 2015 12:48 PM User is offline

Year: 1985
Make: Ford
Model: LTD Crown Victoria
Engine Size: 5.0L
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 25-30
Pressure High: 280-350+
Country of Origin: United States

Polling all experts!

I retrofitted my AC system to R134a on my recently acquired box. Performed the following:
-New Delco evaporator
-New Orifice tube
-New receiver/drier
-New rebuilt ac compressor
-Lines flushed with AC flush fluid, condenser also flushed
-HNBR O-rings everywhere
-PAG46 oil added, 3 oz to evap, 1 oz. to condenser, 3 oz.-ish added to compressor (received dried), 1 oz. to receiver/drier; total charge should be around 8 oz.
-Charge R143a to 2 lbs (32 oz.) which is roughly 20% less than the full R12 charge
-Serviced the AC with a Robinair AC machine.

Problems:
AC blows cold except that I have low suction pressure (20-30 psi) and high discharge (280 psi) at idle. With the engine off idle (1500 RPM), the pressure jumps 35+ on the low side and 350 on the high side. AC remains ice cold. The compressor sounds like it is straining. The receiver/drier gets cold to the touch (almost icy). Does it sound like I have an airflow problem with the condenser?

I'm concerned with the noise. Also, with the fan speed at low, the pressure decreases so low that the low pressure switch kicks the AC compressor off.

Help appreciated!!
Could I have an issue with too much oil?

Dougflas on Tue September 29, 2015 5:26 PM User is offline

Mist the condenser with a water hose and see if the high side drops. You may have an airflow problem with not enough air over the condenser. Could be caused by fan clutch.

mk378 on Tue September 29, 2015 5:55 PM User is offline

20-30 psi low side pressure is ideal. The system is designed to cycle off when maximum capacity is not needed (lower ambients or lower fan speed). Your high side is too high though. Is it a fin and tube condenser? Do you have the fan shrouds still in place?

style86 on Wed September 30, 2015 1:10 PM User is offline

Thanks for the tip. I am running the stock fan shroud with a clutch fan. I will mist the condenser and see how the pressure change. Yes the condenser is tube and fin. Probably going to serpentine style will be better...

Cussboy on Wed September 30, 2015 2:41 PM User is offline

Quote
Originally posted by: style86
I am running the stock fan shroud with a clutch fan. I will mist the condenser and see how the pressure change..

If that drops the pressure, then try a new fan clutch. And clean the front of the condenser if it's dirty.

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