Service manual

Page 12 400 Series Ovens 32Z3769 Issue 1

SW2 Primary Interlock— located on the left hand side of the oven. Directly disconnects

the supply to the microwave generating circuit and thereby cuts off the microwave emissions

from the oven when the door is opened.

SW1 Monitored switch—located on the same assembly as the primary. The Monitor

switch will produce a short circuit across the mains supply if the Primary interlock switch is

faulty, thus blowing the microwave fuse and rendering the oven inoperative.

SW3 The Secondary interlock—located on the left hand side of the oven and like the

primary switch will cut off the microwave emission and will do so even if the primary and

monitored interlock have failed open circuit.

Note: If operation of the Monitor switch has caused the Microwave Fuse to blow, the

Primary and Monitor microswitches must be changed, as they may have been

damaged by the high short-circuit currents involved.

SW4 Convection fan switch—located on the same bracket as the control switch.

This switch is wired in series with the convection motor supply and will disconnect when

the door is opened.

SW5 Control switch—located on the top right behind the display connects to the

logic control PCB on a black and white twisted pair of wires. It is this signal that is used by

the control circuit to determine the door position. A closed contact indicates a closed door.

Door interlock operation

The door on the oven is monitored by five microswitches. Three of these are used in the

conventional “Primary, Secondary and Monitor” switch arrangement shown below, while the fourth

is a low-voltage switch linked directly to the control circuitry and the fifth switches the power to the

convection motor.The switches operate as follows:

Door open position

Fused

Live

LHS

RHS

Control PCB

Convection Fan

Neutral

Output

SW2 Primary

SW5

SW4

SW3 Secondary

SW1 Monitor