Wagoneer L6-242 4.0L VIN M FI (1988)
A/C Signal: Description and Operation
A/C SELECT SIGNAL
When the air conditioning switch is turned ON a voltage signal is sent to the ECU indicating this. The ECU uses this signal to determine the proper idle
RPM.
A/C REQUEST SIGNAL
Once the air conditioning has been turned ON, this signal provides the ECU with information received from the evaporator temperature switch. The
evaporator switch indicates to the ECU when the evaporator is within its temperature range and if it is, then it can cycle the compressor clutch on and off.
The ECU also uses the evaporator switch information to determine the proper position of the idle speed stepper motor depending upon whether the air
conditioning clutch is engaged or disengaged.
