G 2500 3/4 Ton Van V8-350 5.7L VIN K TBI (1995)
Typical Headlamp Schematic
Step 2: Read the Headlamps electrical schematic. This is the step that will save you time and labor. Remember, it is essential to understand how a
circuit should work before trying to figure out why it doesn't.
After you understand how the circuit should operate, read the schematic again. This time keeping in mind what you have learned by operating the
circuit.
Since both LO beams work, you know that the Head/Park Lamp Switch, the YEL wire, the LO contacts of the Headlamp Dimmer Switch, terminal
1E of C100, the TAN wires, and grounds G105 and G109 are all good.
Furthermore, since you saw that the HI Beam Indicator came "ON" when the Headlamp Dimmer Switch was moved to HI, you know that the HI
contacts of the dimmer switch and the LT GRN wire between the dimmer switch and C100 are good.
At this point, you could test for voltage at the RH Headlamp with the dimmer switch in HI. However, it is extremely unlikely that the HI beam
filaments have burned out in both headlamps or that both headlamp connections are bad. The cause must be a bad connection at C100, or a break
in the LT GRN wire between C100 and the RH Headlamp.
You have quickly narrowed the possible causes down to one specific area and have done absolutely no work on the vehicle itself.
Step 3: Find the cause and repair it. Using the Component Location List and the corresponding figure, you can quickly find C100 and the LT
GRN wire, locate the exact trouble point, and make the repair.
Step 4: Check the repair by performing a system check on the Headlamps circuit. This, of course, means making sure that both HI beams, both
LO beams and the HI Beam Indicator are all working.
Now suppose that the symptoms were different. You may have operated the Headlamps and found that the LO beams were working, but neither
the HI beams nor the HI Beam Indicator was working. Looking at the schematic, you might conclude that is unlikely that both HI beam filaments
and the HI Beam Indicator have all burned out at once. The cause is probably the dimmer switch or its connector.
Testing For Voltage
