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.

 

Post your ACTUAL pressure readings at idle and at 1200-1500 RPMs, not your interpretations of them.

 

Everybody eats crow once in a while....I guess it's my turn. Put gauges back on this morning, paying more attention than before.

Ambient temp 95

Static engine off 105/105
Static engine idling 105/105
Engine Idle AC & Fan on MAX 45/265
1200 RPM 35/325

Short Road test...
Ambient 95
AC Vent 45 !!!

I have NO IDEA of where I came up with "OFF THE CHART." The system seems to be working GREAT, cooling better than I can ever remember.
Do these numbers look good to you or what? I am no AC tech and could be missing something.

Thanks much

 

You could be overcharged or the engine cooling fan is not up to par, or the condenser has internal flow problem or an air flow problem.

 

HHott,

Which of my pressures lead you to say these things?

 

Your high side is bit higher than it ought to be. Usually a value around 2.5x ambient (in F) is the typical upper limit.

 

Project,

Thanks for your help. Am going to "let it ride" because the factory manual chart shows a range at 95 degrees of up to 320. The ambient was actually a little higher....maybe 98 degrees which definitely brings the 325 into the acceptable range. I just hope Ford is right!

 

This got me doing more than just thinking. I was getting ready to say that I hadn't seen an operating pressure pressure chart in the service manual sinc the days of R12. I would have been right, too, because I'd never looked in the 04 and newer AC portions of the newer WSMs.

So, I popped open the 04 WSM and, low and behold, the operating pressure charts are back! I've had these discs for three years and never got into the new body style systems.

Sweet! Suction and discharge charts for anything from 70 to 120F.

I'd been going off the ole "rule of thumb".