GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1998 🢒 GMC C-Series Medium Duty Truck B7 🢒 Body and Accessories 🢒 Lighting Systems 🢒 Headlamps Inoperative - High Beams

Step

Action

Value(s)

Yes

No

1
  1. Set the headlamp dimmer switch to the LO position.
  2. Observe the headlamps.

Did the headlamp lowbeam filaments light?

--

Go to Step 2

Go to Step 4

2
  1. Set the headlamp switch to OFF.
  2. Set the headlamp dimmer switch to the HI position.
  3. Disconnect the headlamp dimmer switch harness connector.
  4. Connect a J 39200 between terminals A and D in the headlamp dimmer switch.

Does the DMM indicate continuity?

--

Go to Step 3

Go to Step 5

3

Locate and repair the open in CKT 11 (LT GRN) between terminal A in the headlamp dimmer switch harness connector and terminal B in the right headlamp harness connector.

Is the repair complete?

--

System OK

--

4

Locate and repair the open in CKT 150 (BLK) between S105 and G102.

Is the repair complete?

--

System OK

--

5

Replace the headlamp dimmer switch.

Is the repair complete?

--

System OK

--