TROUBLE DIAGNOSES — Electrical Components Inspection (Cont'd) — Thermo control amp / A/C relay / Thermoswitch

HA-85spec table

Thermo control amp output is inverted: 12V on the meter = compressor OFF (line cold), 0V = compressor ON. Thermoswitch is the condenser-fan thermoswitch (water-temperature triggered) — only fitted to 'hot-areas' spec.

Continued from HA-84

Electrical Components Inspection (Cont'd)

THERMO CONTROL AMP.

Thermo control amp — operating test

1
Run engine, and operate A/C system.
2
Connect the voltmeter from harness side.
3
Check thermo control amp. operation shown in the table.

Thermo control amp — output vs evaporator outlet air temp

Evaporator outlet air temperature °C (°F)	Thermo amp. operation	Tester
Decreasing to 1.5 – 2.5 (35 – 37)	Turn OFF	Approx. 12V
Increasing to 3.0 – 4.0 (37 – 39)	Turn ON	Approx. 0V

Decreasing to 1.5 – 2.5 (35 – 37)

Thermo amp. operationTurn OFF

TesterApprox. 12V

Increasing to 3.0 – 4.0 (37 – 39)

Thermo amp. operationTurn ON

TesterApprox. 0V

A/C RELAY

A/C relay — coil energisation test

1
Check circuit continuity between terminals by supplying 12 volts to coil side terminal of A/C relay.

THERMOSWITCH (For hot areas)

Condenser-thermoswitch operating thresholds

Water temperature °C (°F)	Operation	Continuity
Decreasing to 85 – 91 (185 – 196)	Turn OFF	Does not exist
Increasing to 92 – 98 (198 – 208)	Turn ON	Exists

Decreasing to 85 – 91 (185 – 196)

OperationTurn OFF

ContinuityDoes not exist

Increasing to 92 – 98 (198 – 208)

OperationTurn ON

ContinuityExists

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