Ac Not Cooling Properly

[police interceptor]

98 Ford Crown Vic.

I know there is a hot or high side and a cold/low side to a veh. AC system.
I watched as the tech connected the gauges to the system and saw that the pressure would rise to 55 (I'm not sure of the values), then the radiator cooling fan would come on, then the pressure would fall to 25 then the fan would cut off, then the pressure would immediately begin to rise to 55 again and the process started over again and again and again.

At first they put in freon, then they took it out? (I don't really think they know what they are doing?), and I think they freaked out watching the pressure change.

The AC is not cooling properly. Is the pressure rising because not enough air is passing over the coils to cool the hot/high side, then falling when the fan comes on and cools it?, and, is it normal for the pressure to flucuate so much?

Is the fan going on and off because of the pressure change in the AC system?, or is the pressure changing because the fan is coming on and going off?..or it is "what came first the chicken or the egg?" and is irrelevant??

Bottom Line, IS THIS A FACTOR IN THE FACT THE AC IS NOT COOLING PROPERLY, AND WHAT NEEDS TO BE DONE TO FIX IT?

Thanks in advance!

[ModMech]

Well you MUST have seen the "low side" gauge, and during normal operation, it should never see 55 psi. It should vary between about 15 psi and 30 psi. The "low side" pressure is measured on the suction hose of the A/C compressor, and the fact that your fan is cycling so much along with the high pressures tells me that your system if very much overfilled. You may well have additional problems like low airflow over the condensor core due to debris, a malfunctioning orfice tube, or a bad cut-out switch.

One thing that will cause 55 psi low side readings is if the A/C clutch disengages (cycles off) for an extended period, the system pressure will attempt to equalize (low goes higher, hi goes lower), then the A/C clutch will engage again dropping the low side into the normal range.

Under most circumstances, at moderate humidity and temperature under 95*F or so, the A/C compressor *should* run almost constantly, and the system pressure is "moderated" by the orfice tube in the high side port of the evaparator.

Have your A/C system serviced by a real professional.