Does anyone know how to override or change the A/C clutch shut off point. When I am towing in rolling hills, not big grades, the a/c clutch disengages most of the time when pulling the grade. I am not lacking for power, so I would like to change it so the a/c clutch won't disengage until I am closer to wide open throttle. This thing shuts off the a/c compressor when towing up just about any grade and I can't keep the cab cool. Help??

 

The A/C clutch is cycled via a sensor on the accumulator. This is on the high pressure side of the system and IS NOT related to vacuum levels. It's main purpose is to keep the pressure in the high side within set parameters and will shut off compressor when the high pressure limit is reached. As the pressure bleeds off in the accumulator the switch will cycle closed and the clutch will engage and repeat cycle to build up pressure in high side.

If the sensor is bad you can have whats known as shortcycling or no cycle due to sensor open.

You could remove connector to sensor and bypass BUT YOU WILL END UP WITH A VERY EXPENSIVE REPAIR!!!

Best thing you could do is take it in to a reputable A/C shop and have them go over system.

Larry

 

Larry, what you say is correct for the a/c system basic operation. However my question relates to the part of the system that is designed to disengage the a/c clutch when passing another vehicle or during other high load situations so that maximum power is available. Your further thoughts?

 

what year truck. This may be something that's controlled by the computer.

I'll look in my Chiltons for a diagram and check when I get home from work.

 

Pulled out the manual....

Book goes 80-96 but might help.....


Wiring as follows 92 to 96 F-Series and Bronco: Yours might be different......

FROM CLUTCH blk and blk-yel wires go to

A/C CLUTCH RESISTOR DIODE

In the Clutch Resistor box are 6 wires shown as follows:

1. BLK
2. BLK-YEL
3. BLK
4. PNK-LT BLU
5. BLK-YEL
6. BLK-YEL


3 & 6 are from Clutch

1.) is Ground E (GAS), Ground B (Diesel W/O Leece Neville Alternator), Charge Ind Lamp Relay (W Leece Neville Alt)
2.) Inst Cluster PIN A-10 (Ex. 4.9L)
3.) A/C Comp Clutch
4.) PCM PIN #10
5.) Clutch Cycling Pres Sw.
6.) A/C Comp Clutch

NOTE: 1,2,&3 are joined together. 5&6 are joined together

Diode off 3 ties to #4 and then to resistor between 4 & 5/6. Current flow thru Diode is from 3 to 4.

Now on to the Pressure switch
Blk-yel from Pin 5 on Resistor Diode box to Pressure switch....other side of switch is Purple to AC Heater control assy and PCM PIN 43 (Gas) (DIESEL NOT USED). AC HEATER control switch (MAX (on)- AC(on) -Vent(off)-Heat(off)-Mion)-Def(on)is fed from BRN-WHT wire from Fuse #6

The only thing I can think of is that the PCM sees certain parameters and shuts off the clutch under full load. Personally, if it's part of the "brain" I wouldn't mess with it. Guess you'll have to live with it.

Our C*^&% van doesn't do this on hard load, neither does her pontiac. And my F-150 doesn't have A/C. Maybe its a Ford thing.

Larry

 

The truck is a 2001, F150 / 7700, 5.4, 4R100. I do think it is computer controlled. I live in the south so it is a definite issue for me. It would not be a problem if it only shut off the a/c clutch under full load, but it does it at about 60% load. This along with the other problems Ford has not yet fixed may result in a short relationship with this vehicle. I am going to keep looking for some way to fix it. Thanks for looking Larry.