Component Diagnostic Charts/Tests

Fig. 016 - Wiring Diagram for Chart C-10D A/C WOT Relay Check.:

CHART C-10D, A/C WOT RELAY CHECK (5.0L AND 5.7L)

The A/C Wide-Open Throttle (WOT) cut-out relay is used to disengage the A/C compressor clutch during hard acceleration. This is accomplished by an ECM controlled relay.
The relay has a normally open set of points. When energized, the points close to allow compressor clutch coil operation. The relay coil is supplied 12 volts by ignition and the ECM completes the circuit to ground to energize the relay. When a high TPS voltage is input to the ECM, the relay is de-energized by the ECM to cut off compressor clutch coil operation.

Fig. 013 - Chart C-10D A/C Wide Open Throttle Relay Check.:

1. Checks for normal A/C compressor operation at idle. Compressor should normally be "on."
2. Checks for A/C compressor cut-out at wide open throttle signal (full TPS). Compressor should normally go "off."
3. Checks for signal from ECM to de-energize A/C cut-out relay. If test light is "on," there is a grounded ECM circuit on ECM. On B and G series a 3rd gear A/C cut-out inhibit is used. If the normally open switch is closed - no A/C cut-out will occur. If test light is "off," fault is relay connection or relay.
4. By jumpering relay connector terminals, the relay contact points are by-passed. This determines whether the problem is ECM/relay related or not. If the compressor remains "off," the fault is in A/C power flow, compressor in "on" after jumping connector terminals, fault is ECM/relay related.
5. Determines if fault is in ECM or relay circuits. By connecting a test light across relay connector terminals, a normal signal to energize the relay can be detected if the test light is "on." If the test light is "off," the fault is in ignition feed to relay or ECM wiring or ECM.