I bought a 2005 Ford Taurus last month with a bad A/C clutch. I had a friend, who says he knows about such things, replace just the clutch. He says he lost no refrigerant, which should be right. The A/C blows cold OK regardless of the ambient temperature, but the new clutch clicks in and out. I was of the opinion that this was caused by a low charge. My (not always right) friend thinks it’s normal, due to the cooler weather. I THINK the compressor should run all the time, and the car’s interior temp is regulated by the flapper doors. I have no way to capture the present charge and weigh in the exact amount needed. I have accurately weighed in an additional 8 ozs, with a good digital scale, and it still clicks in and out. I have readings of 125/25, but the outside temp is only 50F this morning.
The a/c compressor will cycle on and off as normal operation. Some cars run the compressor continually and use an expansion valve to control the flow and pressure of the refrigerant in the system. Some cars cycle the compressor on and off to control flow and pressure of refrigerant.
You don’t need to evacuate and weigh the refrigerant to achieve a proper charge. Just need a set of gauges. Although I need more info than just pressure readings.
@asemaster Which kind is the '05 Ford Taurus? I think it has an orifice tube, not an expansion valve, but I’m not sure. I know it has a flapper door actuator as I have had to replace one of those before. They are easy to see and replace if you remove the stereo module from the dash.
On hot days, and other cars, I have seen pressures of double what I see today. Those Taurus compressor clutches were not cycling. I know 125/25 is not high enough to cause a lock up.
Your Taurus uses a fixed orifice, and the cycling is controlled by (if I remember without looking at some service info) low side pressure, evaporator temperature, and high side pressure.
Your pressures of 125high/25low may seem a little low, even for ambient temp of 50*, but I’d want to know a/c vent temp, whether radiator fans are off, low, or high, static pressures, and how rapidly the compressor cycles and how quickly it pulls low pressure down when it comes on… You’ve already added half a pound to a system that can’t hold more than 2, so I wouldn’t add any more without being sure it needs it. Overcharging leads to high head pressures which can kill your compressor the first hot day you get.
Although the compressor had been cycling even when the ambient temp was about 75F the last few days, I went out to the car a few minutes ago in an attempt to answer @asemaster 's questions. The ambient temp is now 64F. The compressor doesn’t appear to be cycling at all at 850 RPM idle . It had a vent temp of 38.7F, with the blower on high and vents set to recirculate for ten minutes or so. The radiator fans were on after it had run at idle for a couple of minutes. Unfortunately I had to return the A/C gauges to the shop I borrowed them from before he closed at noon. I can’t tell you what the pressures are at this time. He won’t be open again until Monday.
Since it’s not cycling any longer, I’m going to pronounce it fixed.
If the 125/25 readings you show are with the A/C compressor engaged then there is a problem because both readings are too low no matter the ambient temperature.
With the engine and A/C off you should see about 120 PSI static pressure on both high and low sides.
Running on a cool day you should see about 225-240 on the high side and 30-35 on the low. Offhand, sounds like a low charge to me.