A/C compressor cycle time

Guys with the v6, next time you're driving home with the A/C on, please notice how frequently the compressor cycles on and off and post back.

Mine is cycling quickly, about 10 seconds on, 20 seconds off, when it's on low. Maybe 20 seconds on, 20 seconds off when it's on high. Right as the air starts to get really cold it cycles off. Even with the air on high, if it's only about 80 degrees outside it cycles so quickly that the air doesn't get that cold. By memory it didn't used to do this. It's not over charged, I've had it evacuated and recharged by the local shop, but the behavior is the same. They claim it's normal but I remember the A/C blowing colder and the compressor running longer in-between cycles, so I would love to compare to other trucks.

 

Sounds like its still low on refridgerant or bad low pressure switch.

 

yep, still low or a faulty low pressure switch causing it to short cycle.

the only time it should ever short cycle under normal operating conditions, is when it is used in cold weather conditions for defrost or something where the outside temps cause lower system pressures

 

What pressure on the low side should trigger the low pressure switch?

I had some time yesterday to check it out, and with the A/C on low, about 2500 RPM and a fan blowing in the front of the truck (to simulate driving) I can get the low side pressure down around 20-25psi and the compressor is still running. The compressor will turn off with the pressure up at 25psi+, so I don't think it's cycling due to the low pressure side. I'm wondering if there is a temperature switch on the evaporator that is tripping prematurely?

With the AC on high, the low side pressure is around 35-40psi and the high side is around 250psi, 90F ambient temp and humid, 2000-2500 RPM and extra fan blowing on the front of the truck. Without the external fan blowing on the front of the truck I was seeing high side pressures up to 300psi. It's difficult to compare absolute pressure values to the service manual since it seems to be affected so much by how much air moves through the front of the truck, which varies greatly by how hot the motor is (how much the fan clutch is locked up).

 

Sub'd. Mine is doing this exact thing but only when its really hot outside.

--Dan