Working on an issue with intermittent a/c compressor operation. What is a WOT switch and where is it physically located.

 

What year Ranger?

Its often called AC clutch relay in later years

WOT(wide open throttle) relay name was used pre-1990 and up to about 1997,
In these year the dash AC controller switch sent 12volts thru the WOT relay to turn on compressor

Computer would OPEN WOT Relay to shut off AC compressor when driver wanted full power, i.e. to pass or when pulling loads up hill

AC Clutch relay did pretty much the same thing, but it was also used to turn AC compressor on when computer became AC Controller, in 1998 and up
In these years the Dash AC switch was hooked to the computer, when computer sees AC ON from the dash switch it activates the AC Clutch relay to turn on the compressor, and then it can turn it off when driver wants extra power, i.e. WOT

1992 and up it should be in engine fuse box, or under fuse box
Earlier its the relay with the black base on the inner fender

 

Thanks for the response, RonD. It's a 2002 4L RWD.

If I am understanding you correctly, the WOT signal comes from a computer. Is that the ECM?
What tells the computer the throttle is wide open?

 

TPS(throttle position sensor) tells computer that the driver is at WOT, TPS get 5volts from computer(ECM or PCM), it sends back under 1 volt when throttle is closed, above 4.5volts at WOT

AC Clutch relay will be in the engine fuse box, 47A, mini relay


There are two pressure switches on the AC "freon" hoses
A low pressure switch so compressor doesn't "run dry"
A High pressure switch so AC hose don't explode if system gets blocked

These two switches are the GROUND that is used to Close AC relay

Ground-----------------pressure switch----------------pressure switch--------------------------------Computer

When you turn on the AC switch in the cab, the computer passes that GROUND to the AC relay and it CLOSES sending 12volts to the clutch on the compressor

If either pressure switch is opening and closing because of marginal pressure then compressor would cycle on and off as well

 

Thanks for the details, RonD. Most helpful in resolving my ac problem. After checking and eliminating all of the electrical points of control as the problem, I found that the clutch is not pulling in when the compressor gets hot. Couple taps with a screwdriver handle and it pops right in. Figure the air gap is too wide (which it certainly appears to be) or the field coil is weak.

 

Air gap was an issue on older Ford AC Clutches pre-1990s, newer ones not so much
My guess would be the coil............or test the voltage at the coil, should be battery voltage, so 13.5v to 14.5v with engine running, if there is a corroded connector voltage in the 12v circuit, it could drop under 9v when warmed up so clutch can't engage without a nudge