Cooling System: Testing and Inspection

TROUBLESHOOTING

1. If coolant temperature is low (below 181°F), proceed as follows:
a. Turn ignition switch on and ensure cooling fan is not operating.
b. If fan is operating, a faulty fan relay and/or temperature switch is indicated. Check for separated electrical connectors or severed wire between relay and temperature switch.
c. Disconnect temperature switch wire, then check that fan rotates.
d. If fan does not rotate, check fan relay, fan motor, ignition relay and temperature switch.
e. Connect temperature switch wire.
2. If coolant temperature is high (above 194°F), proceed as follows:
a. Raise engine temperature to above 194°F, then check that fan rotates.
b. If fan does not rotate, replace temperature switch.

COMPONENT INSPECTION

1. Using a suitable ohmmeter, check temperature switch, located at radiator lower tank, for continuity. No continuity should exist when water temperature is above 194°F. Continuity should exist when water temperature is below 181°F.

Fig. 4 Main relay connector. MR2 & 1987-88 Corolla FWD:

2. On 1987-88 models, inspect main relay, located in engine compartment relay box as follows:
a. Using suitable ohmmeter, ensure continuity exists between terminals 1 and 2, Fig. 4.
b. Ensure continuity exists between terminals 3 and 5.
c. Ensure no continuity exists between terminals 3 and 4.
d. If relay does not perform as outlined above, replace relay.
e. Apply battery voltage across terminals 1 and 2, then ensure continuity exists between terminals 3 and 5 and no continuity exists between terminals 3 and 4.
f. If relay does not perform as outlined in step e above, replace relay.

Fig. 1 Checking Cooling Fan Motor Relay:

3. On 1987-88 models, check fan motor relay, located in engine compartment relay box, as follows:
a. Using suitable ohmmeter, ensure continuity exists between terminals 1 and 2, Fig. 1.
b. Ensure continuity exists between terminals 3 and 4.
c. If no continuity exists, replace relay.
d. Apply battery voltage across terminals 1 and 2, then check that no continuity exists between terminals 3 and 4.
e. If continuity exists, replace relay.

Fig. 2 Checking fan motor:

4. Connect a suitable ammeter and battery to fan motor connector, Fig. 2. Ensure motor rotates smoothly and current is 3.2-4.4 amps.