In this tutorial I'm gonna' explain how to test the low-beam circuit of the headlight switch. So, if your 1997-1998 Ford F150 (F250, and Expedition) has a ‘no low-beam headlights’ problem, then this tutorial will help you troubleshoot it.
All the test steps are explained in a step-by-step manner and are done with a multimeter.
Contents of this tutorial:
- Headlight Switch Troubleshooting Basics.
- TEST 1: Checking Fuses #7 And #8 Of The Power Distribution Center.
- TEST 2: Checking Fuses #16, #26, And #28 Of The Dash Panel Fuse Box.
- TEST 3: Making Sure The Headlight Switch Is Getting Power.
- TEST 4: Jumpering The Headlight Circuit.
- TEST 5: Testing The Multi-Function Switch.
- TEST 6: Testing The Continuity Of The Headlight Circuit.
- Where To Buy The Headlight Switch And Save.
- More Ford 4.6L, 4.8L Tutorials.
NOTE: The headlight switch, covered by this tutorial, is shared by the 1997-1998 Ford F150, 1997-1998 Ford F250 and the 1997-1998 Ford Expedition.
NOTE: If you need to test the park-lamps circuit of the headlight switch, see this tutorial: Testing A No Park-Lamps Problem (1997-1998 Ford F150).
Headlight Switch Troubleshooting Basics
In a nutshell, this is how the headlight switch functions:
- Has power available at all times for the head-lamps on the dark blue with orange stripe (DK BLU/ORG) wire of the black 7-terminal connector.
- When you turn the headlight switch to the ‘head-lamps on’ position, the switch now channels battery power (from the DK BLU/ORG wire) to the red with yellow stripe (RED/YEL) wire of the black 7-terminal connector.
- The RED/YEL wire now feeds this battery power to the multi-function switch (commonly known as the wiper switch).
- If the multi-function switch is set in its LO beam selection, it now channels this battery power to fuses 26 (right head-lamp) and 28 (left head-lamp) of the dash panel fuse/relay box. Otherwise, the multi-function switch stops battery power from reaching the fuses.
- Once fuses 26 and 28 get battery power, then battery power is now available at the right headlamp (DK GRN/ORG wire) and left headlamp (DK BLU/WHT wire).
- With battery power is now available at the right headlamp (DK GRN/ORG wire) and left headlamp (DK BLU/WHT wire), the low-beam circuit of the head-lamps now comes ON.
The headlight switch, on the 1997-1998 F150 (F250, and Expedition) has three connectors. The one that we're gonna' worry about, to test the headlights, is the 7-terminal black connector.
In the table below you'll find a brief description of the two terminals we need to test in this tutorial:
|Black 7-Terminal Headlight Switch Connector|
|4||Dark Blue w/ Orange stripe (DK BLU/ORG)||Battery (+) In (Head-Lamps)|
|5||Red w/ Yellow stripe (RED/YEL)||Battery (+) Out (Head-Lamps)|
Let's get started with the first test.
TEST 1: Checking Fuses #7 And #8 Of The Power Distribution Center
The first thing we're gonna' do is check 2 specific fuses in the Power Distribution Center (under-hood fuse/relay fuse box) that feed the headlight switch with power for the headlight and park-lamp circuits.
If these fuses are OK, then we need to check the condition of 3 fuses on the dash panel fuse box in the next test section.
OK, let's get started:
Locate and check fuse #7 (15 A) of the underhood fuse box.
Fuse #7 feeds battery power to the park lamps circuit of the headlight switch.
Locate and check fuse #8 (30 A) of the underhood fuse box.
Fuse #8 feeds power to the headlights circuit of the headlight switch.
Let's interpret your test results:
CASE 1: All fuses are OK. So far so good, since this is the correct and expected test result.
Your next step is to go to: TEST 2: Checking Fuses #16, #26, And #28 Of The Dash Panel Fuse Box.
CASE 2: Found a blown fuse. Replace the fuse and retest.
If the fuse gets blown again when you turn on the head light switch, then your next step should be remove the headlight switch and test the continuity of the power circuit for shorts to Ground between the fuse-box and the headlight switch connector.