Courtesy Light Extender

In the Ducato the dual front courtesy lights have two control switches. One selector turns on the left or right courtesy light while the other selector alters the courtesy light operation as follows:

• mode A: light permanently on;
• mode B: courtesy light (turns on/off by opening/closing one of the front doors);
• mode C: light always off.

In "courtesy light" mode, the courtesy light activation/deactivation command comes from one of the front door pin switches in the door pillars. This is shown in the following schematic which includes a location snip.

Fiat wiring colours (Italian) are here.

The Extender Circuit

The Ducato courtesy light wiring is basically simple. It is the same as was in Holdens of 35 years ago, and this allows use of a circuit I published in March 1993 in Electronics Australia, Circuit & Design Ideas, based on an earlier article in that magazine before 1973.

When one of the front doors is closed, instead of the courtesy light instantly turning off, plunging the cab into darkness, the added circuit causes the light to stay on and fade to off over about 10 seconds.

The circuit operates as follows:
When the driver's door is opened, the switch (SW1 - "I016" in the Ducato) in the door jamb closes and earths the courtesy light, switching it on. Before this switch closed, capacitor C1 was already charged to the supply voltage. Once closed, SW1 rapidly discharges C1 via diode D1. As soon as the door is closed again, transistors Q2 and Q1 turn on, and connect the courtesy light to ground, keeping it switched on. Capacitor C1 gradually charges up via resistor R1, and eventually turns off the transistors. The values of R1 and C1 were chosen to give a useful light level for about 5 s, followed by a decreasing light level for a further 8 s.

With some pruning of the lugs of the 2N3055, the whole of the circuit can be fitted into a plastic 35 mm film canister. It is located above the fuse panel on the driver's side and wired across the pin switch in the door jamb using an insulation-displacement connector for the high-side wire and a convenient earth connection near the fuse panel.

LINKS

• Fiat Ducato http://www.fiatforum.com/ducato/

Light Extender

When the door closes, the courtesy light fades to off in ~10 seconds.

35mm film canister holding the light extender is above the driver's side fuse block.

The components of the light extender are wired directly onto the 2N3055.