Checking pre-heating device

CHECKING PRE-HEATING DEVICE

General operating check

a) Connect a test lamp in parallel between the heater plug current cable and an earth point.

Turn the ignition switch to the ON position.

The test lamp should come on. If the unit is operating correctly, it should go out after around 27 secs at a temperature of 20°C.

The heater plugs warning light should only remain on for 4 to 7 secs (at a temperature of 20°C) and then go out if the unit is working properly.

28. Pre-heating control unit
29. Heater plugs

b) Turn the ignition switch to the ON position once again. When the heater plugs warning light goes out START UP the engine: the test lamp in the engine compartment should remain on for ~ 18 secs (at 20°C). This shows that the control unit is working perfectly. If this is not the case, replace the control unit as it must be faulty.

NOTE See the diagram for checking corresponding times and temperatures.

Checking heater plugs supply circuit

Connect a test lamp between contact 1 (large diameter black cable) of the control unit and an earth point: the test lamp should come on. If it does not, there is a break in the circuit between the battery and the control unit which should be located and remedied.

Then connect the test lamp between the cable coming out of contact 5 and an earth point. Then start up the engine: if the test lamp does not come on (the engine will not start if cold) the electrical connection between the 4 heater plugs should be disconnected and the above described check carried out for each of the heater plugs, one at a time. This allows the defective plug which is short circuited to be discovered and replaced.

Checking control unit supply

Disconnect the multiple connector from the control unit before carrying out the checks listed below.

Connect a test lamp between terminal 3 of the multiple connector and an earth which is working properly.

When the ignition switch is turned to the ON position the test lamp should come on. If this is not the case, check the continuity of cable 3, coming from terminal 15/54 of the ignition switch and check that the ignition switch is not faulty.