A/C Signal: Description and Operation
A/C "ON" SIGNALPURPOSE
Provides the Engine Control Module (ECM) with A/C request signal.
OPERATION
This signal tells the ECM that the A/C selector switch is ON. ECM adjusts the idle speed before turning ON the A/C clutch. If the signal is not available to the ECM, A/C compressor will be inoperative.
Compressor Control Signal
DESCRIPTION
This system consists of a high pressure cut-out switch, Air Conditioning (A/C) compressor relay, A/C thermo switch relay, A/C controller and the compressor.
OPERATION
The high pressure cut-out switch (normally closed), opens when the head pressure gets too high. This will disable the A/C clutch, before damage can occur to the compressor or other A/C components.
When A/C control switch is "ON" and the high pressure switch and thermo switch are closed, a request signal is sent to the Engine Control Module (ECM). The ECM will then energize the A/C clutch through the A/C clutch relay. The A/C controller which is separate from the ECM will then turn the A/C cooling fan "ON".
The A/C controller controls the A/C cooling fan, as well as sending a signal to the ECM on model equipped with automatic transmission.
The ECM will disable the A/C clutch during Wide Open Throttle, or high power steering loads. The ECM has a slight delay for clutch engagement to allow for the idle to slightly increase.