Automotive Air Conditioning Information Forum (Archives)

tperk100 on Sun July 24, 2011 2:42 PM

Year: 04
Make: Ford
Model: F350
Engine Size: 6.0
Refrigerant Type: 134a
Ambient Temp: 100
Pressure Low: 45
Pressure High: 225

Starting from an evacuated system, I tried to weigh and install my refrigerant. Turns out my refrigerant hose on my gauge set had a leak so only a portion of my 134a actually went into the system. When I was finished and realized that the system was not cooling, I put the gauge set back on and this time was paying attention to the pressure readings. In 100 degrees, AT IDLE, the reading were well below the acceptable range on the chart.

So there I was right back to guessing how much refrigerant the system needed. I started adding refrigerant, AT IDLE SPEED. After adding about 20 oz, I was getting readings in the middle to the high part of the recommended range....seemed real good and now the system was cooling well.

HOWEVER, when I increase rpm to about 1200, the pressure readings go OFF THE CHART!...way high! So I am trying to decide if I have over charged the system. The FORD factory manual says to charge the system at IDLE speed, which is what I did and got good readings at this speed.

Is it normal for pressures to go REAL high at faster than idle speeds. The system is cooling REALLY WELL with over a 40 degree temp drop across evaporator. Am I over charged?

Any comment/help will be appreciated.

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Tom P

Dougflas on Sun July 24, 2011 4:40 PM

your fan clutch may be weak. 1500 rpm, what are the pressures? If the high side is too high, mist the condenser with a hose. If the pressure drops radically, look at the fan clutch. Common problem.