Incandescent Bulb Testing

INSPECTION

1. Remove the bulb and inspect it visually. If the filament is burned out or the glass envelope is loose in the base, replace the bulb.
2. To check the bulb accurately, perform the following:
Connect the bulb directly to the battery. Observing polarity is not necessary in this case. Connect one wire to the bulb's power contact and the other to the bulb body. If the bulb does not light, replace it. Also check the bulb body for corrosion. If there is rust, clean it with abrasive paper.
3. If the bulb is serviceable, insert it into the socket and switch it on. If the bulb does not light, check the power supply with a test lamp. To do this, connect the test lamp to ground. Connection is made as follows. Connect one lead of the test lamp to a ground point on the engine (clean bare metal) or directly to the negative battery terminal. Connect the other end of the test lamp (+) either to the live connector or pierce the live cable. If the test lamp now lights but the bulb being checked does not, there is an open circuit in the ground wire to the bulb. To check, attach the ground wire to the bulb socket. The bulb should now light.
4. If there is no voltage in the live cable to the bulb and the test lamp does not light, the switch may be faulty. Check the switch.
5. Otherwise, check the bulb module.