Making An LED Test Light

Many of the electrical tests in this manual require the use of a special LED test light, since the use of a more conventional test light with incandescent bulb can damage sensitive electronic circuits in the ignition, fuel injection, and emission control systems. One suitable test light is Volkswagen special tool no. US 1115 (order no. TU1 115 000 28 ZEL).

A lower-cost alternative is to make an LED test light, using parts available from an electronics supply outlet. Assemble the components as shown in Fig. 3-6. Use a needlenose plier to hold the parts and to act as a heat dam while soldering, as described above in Wire Repairs. Insulate all connections with heat-shrinkable tubing or electrical tape.

Fig. 3-6.

Do-it-yourself LED test light for safe testing of ignition, fuel injection, and emission control circuits.