Switch unit - testing

Ignition system - transistorised type / Switch unit - testing

1 When making this test, the coil must be in good condition.

2 Remove the plastic cover on the right-hand side of the plenum chamber for access to the switch unit (see illustrations).

4.2a Carefully prise free plastic cover . . .

4.2b . . . for access to ignition switch

3 Disconnect the multi-plug from the switch unit and connect a voltmeter between terminals 4 and 2 (see illustration).

4.3 Voltmeter connection when testing ignition switch unit

4 Switch on the ignition and check that battery voltage, or slightly less, is available. If not, there is an open-circuit in the supply wires.

5 Switch off the ignition and reconnect the multi-plug to the switch unit.

6 Pull the multi-plug from the Hall sender on the side of the distributor (see illustration), then connect a voltmeter across the low tension terminals on the coil (see illustration).

4.6a Multi-plug connection to Hall sender on side of distributor

4.6b Voltmeter connection to coil when testing ignition switch unit and coil

7 Switch on the ignition and check that there is initially 2 volts, dropping to zero after 1 to 2 seconds. If this is not the case, renew the switch unit and coil.

8 Using a length of wire, earth the centre terminal of the distributor multi-plug briefly.

The voltage should rise to at least 2 volts. If not, there is an open-circuit or the switch unit is faulty.

9 Switch off the ignition and connect the voltmeter across the outer terminals of the distributor multi-plug.

10 Switch on the ignition and check that 5 volts is registered on the voltmeter.

11 If a fault still exists, renew the switch unit.

12 Switch off the ignition, remove the voltmeter and reconnect the distributor multi-plug.