Is my system overcharged or undercharged?

fortee9er on Thu April 22, 2010 9:43 PM

Year: 1994
Make: Ford
Model: Ranger
Engine Size: 2.3
Refrigerant Type: 134a
Ambient Temp: 73
Pressure Low: 25
Pressure High: 200
Country of Origin: United States

My 1994 Ford Ranger has a habit of getting very cold and then cycling off for several minutes before cooling again. This can take anywhere from 10 to 15 minutes. Today for the first time I put a set of a/c gauges and observed until it cut out. The problem is I don't know what is causing it to cut out - too much or too little freon.
Checked static pressure at 73 F - low side = 96 psi, high side = 100 psi.
Car idling @ 800 rpm, ambient temperature 73 F - low side pressure = 30 psi, high side pressure = 200 psi. Blower speed full speed and set to max with doors closed and windows open.
Center air vent temperature 42.4 F - after 10 - 15 minutes.
After nearly half hour with constant pressure readings and vent air temperature staying @ 42 F, I increased engine speed rpm to about 2500 RPM air vent temperature steadily dropped to 32 F and then the compressor cycled off. At this point the low pressure had dropped to 25 PSI but the high side pressure remained @ 200 psi.
This my first attempt at diagnosing and a/c problem and could sure use help.
Thanks in advance for your help.
Jorge

Chick on Fri April 23, 2010 1:26 AM

Your cycling switch will shut it off around 25psi, that is normal, but several minutes before it comes back on could be a clutch gap issue, when it cycles off and the low side pressure goes up to around 40, and it doesn't come back on, tap the front of the clutch with a heavy screw driver and see if it draws in, if it does, you may need to adjust the clutch gap, be careful of the belts when it's running..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

fortee9er on Fri April 23, 2010 11:47 AM

Originally posted by: Chick
Your cycling switch will shut it off around 25psi, that is normal, but several minutes before it comes back on could be a clutch gap issue, when it cycles off and the low side pressure goes up to around 40, and it doesn't come back on, tap the front of the clutch with a heavy screw driver and see if it draws in, if it does, you may need to adjust the clutch gap, be careful of the belts when it's running..

The low side pressure never got to @ 40 PSI all the time I was doing this observation/test/experiment. It always stayed @ 30-35 psi while the engine idled. Pressure then dropped to 25 psi when I increased engine rpm. After the high rpm (@ 2500) run the pressure returned to 30 -35 psi before I shut off the engine.

Edited: Fri April 23, 2010 at 11:49 AM by fortee9er

mk378 on Fri April 23, 2010 3:27 PM

For Chick's test, you need to get the compressor to cycle off first, then watch what happens while it is off but the engine and A/C are still on.

Or are you're saying the low side pressure does not rise even after the compressor has been disengaged for some time? That could be the orifice tube icing up due to having a large amount of water in the system, or some other way it's blocked. The pressures should equalize while the compressor is off by flowing from the high side to the low side through the OT. Within less than a minute, the low side pressure should rise above 40 and the switch should start the compressor again.

fortee9er on Fri April 23, 2010 6:02 PM

Chick you were absolutely right! On the way home from work I stopped at an automotive a/c shop the guy there took a look under the hood and the compressor cluthc and said "you havre too much gap".
He removed the front plate and a small washer to adjust the gap and sent me on my way.
Thanks
Jorge

HVargas on Fri April 23, 2010 6:08 PM

Glad to hear you got it fixed.

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