R-963 (serv.man2) - Sharp Home Appliance Service Manual (repair manual). Page 16

R-953/963M - 14

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of the thermal cut-out. Then using an ohmmeter, make a
continuity test across the two terminals as described in the below.

Table: Thermal Cut-out Test

Temperature of

Temperature of

Indication of ohmmeter

        Parts Name

 "ON" condition

"OFF"condition

(When room temperature

(closed circuit).

(open circuit).

is approx. 20˚C.)

Thermal cut-out 125˚C

This is not resetable

Above 125˚C

Closed circuit

Thermal cut-out 170˚C (GRILL)

Below 155˚C.

Above 170˚C

Closed circuit

Thermal cut-out 170˚C (CONV.)

Below 155˚C.

Above 170˚C

Closed circuit

If incorrect readings are obtained, replace the thermal cut-out.

An open circuit thermal cut-out (MG) indicates that the magnetron has overheated, this may be due to
resistricted ventilation, cooling fan failure.

An open circuit thermal cut-out (GRILL) indicates that the oven cavity has overheated, this may be due
to no load operation.

An open circuit thermal cut-out (CONV.) indicates that the convection fan motor winding has over
heated, this may be due to resisted ventilation or locked cooling fan or locked convection fan motor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.
Disconnect the connector B from CPU unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No's C1 and C3 of the thermistor harness.

Room Temperature

Resistance

20˚C - 30˚C

Approximately 359.9 k

Ω

 - 152 k

Ω

If the meter does not indiicate above resistance, replace the thermistor.

CARRY OUT 4R CHECKS.

CARRY OUT 3D CHECKS.

Disconnect the leads from the motor. Using an ohmmeter, check the resistance between the two
terminals as described in the table below.

CARRY OUT 3D CHECKS.

Disconnect the leads from the terminals of noise filter.
Using an ohmmeter, check between the terminals as described in the following table.

If incorrect readings are obtained, replace the motor.

CARRY OUT 4R CHECKS.

Table: Resistance of Motor

Motors

Resistance

Fan motor

Approximately

293 

Ω

Turntable motor

Approximately

15 k

Ω

Convection fan motor

Approximately

288 

Ω

Damper motor

Approximately

11 k

Ω