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Junior Member
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37 Posts
Discussion Starter #1
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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Super Moderator
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4,247 Posts
A/C pressure should not vary by engine speed more than 10-20 PSI or so.

I am not familiar with the layout on your specific vehicle but a restricted condensor would be high on my list of suspects along with a restricted orifice tube.

If you had a major compressor failure in the past, I can almost assure you the evap is junk.
 

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Junior Member
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37 Posts
Discussion Starter #3
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
 

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Senior Member
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1,836 Posts
There is a possibility that the orfice was partially restricted when you got the reading.
Since you have the equipment - if it will reach tape it on the windshield and get a reading rolling 40-50 mph on the road. My preferred suction pressure is 28 to 32 and the head should drop on the road. Several systems have taken several min to stabilize so I run about 10 min. If the head is still 325 on the road the condenser is probably partially pluged with bugs.
 

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Junior Member
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37 Posts
Discussion Starter #5
Key,

Thanks for your suggestion, but I think, with my whopping 50 degree temp drop at the AC vents, I am going "let it ride" and just drive.
 
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