G 20 Van V6-262 4.3L VIN Z (1993)
Repeat the System Check to verify the fault has been corrected and that no other faults were induced during the repair.
EXAMPLE:
A customer brings in a vehicle and says that the HI beams do not work.
Step 1: Perform a system check on the headlight circuit. You may discover that both LO beams operate. In "HI," you may notice that the HI Beam
Indicator comes on, but neither HI beam operates.
Fig. 1 Typical Headlights Schematic
Step 2: Read the headlights electrical schematic, see Fig.5 This is the step that will save 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 Headlight Switch, the YEL wire, the LO contacts of the Headlight 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 headlight Dimmer Switch was moved to "HI," you know that the HI
contacts of the Headlight Dimmer Switch and the LT GRN wire between the Headlight Dimmer Switch and C100 are good.
At this point, you could test for voltage at the RH Headlamp with the Headlight Dimmer Switch in "HI." However, it is extremely unlikely that the
HI beam filaments have burned out in both headlamps, or that both headlamps 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 fault 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 headlights 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
