A/C Question
06-24-2019, 09:35 PM
#11
Senior Member
What do you have the blower fan at in the truck? If its at 1, the compressor kicks on and off. Anything over 2, its always on (this is a standard design). Also of note: Ford programmed the ECU to have the compressor on for two seconds at startup for certain conditions to push liquid coolant that may have accumulated in the compressor. (truck being off for 8 hours is one of them)
Last edited by ShirBlackspots; 06-24-2019 at 09:37 PM.
06-25-2019, 12:10 AM
#13
This is false. When the AC is on, the compressor will continue to run as long as the pressures remain within the limits of the cycling and safety switches. Fan position has nothing to do with it. Temperature is controlled via blend door position.
06-25-2019, 12:17 AM
#14
Senior Member
Well, I do know that when I have the AC on, and its cool outside, the compressor cycles (on for 30 seconds/off 30 seconds). It does stay on constantly when its hot outside (after the truck has been running for a minute or two), but this is what my truck has always done.
06-25-2019, 06:54 AM
#15
Well, I do know that when I have the AC on, and its cool outside, the compressor cycles (on for 30 seconds/off 30 seconds). It does stay on constantly when its hot outside (after the truck has been running for a minute or two), but this is what my truck has always done.
Compressor duty cycle is wholly dependent on the LOAD on the system. The rate of heat transfer is going to cause the pressures to change and that is what triggers the pressure switches. Under benign conditions, the compressor only has to operate for a few seconds before cycling off for a while. When the load is very heavy (HOT!), the compressor will run continuously.
Ford's service manuals, at one time, also included graphs for duty cycle vs. temps to give a tech an idea of what rate of cycling to expect under various conditions.
06-26-2019, 12:37 AM
#16
Those are normal observations.
Compressor duty cycle is wholly dependent on the LOAD on the system. The rate of heat transfer is going to cause the pressures to change and that is what triggers the pressure switches. Under benign conditions, the compressor only has to operate for a few seconds before cycling off for a while. When the load is very heavy (HOT!), the compressor will run continuously.
Ford's service manuals, at one time, also included graphs for duty cycle vs. temps to give a tech an idea of what rate of cycling to expect under various conditions.
Compressor duty cycle is wholly dependent on the LOAD on the system. The rate of heat transfer is going to cause the pressures to change and that is what triggers the pressure switches. Under benign conditions, the compressor only has to operate for a few seconds before cycling off for a while. When the load is very heavy (HOT!), the compressor will run continuously.
Ford's service manuals, at one time, also included graphs for duty cycle vs. temps to give a tech an idea of what rate of cycling to expect under various conditions.
I believe the reason that the duty cycle graphs have been replaced with the operating pressure chart is because the compressors generally don't cycle anymore. Typical low pressure cut off is around 22psi, which is well below evaporator freeze up. Pretty rare for a fully charged system to hit 22psi, except in cooler weather when the defrost is running. At that point the customer would be unlikely to notice the cycling...