Testing A No Low-Beam Headlights Problem (1997-1998 Ford F150)

TEST 4: Jumpering The Headlight Circuit

In this test section, we're gonna' jumper female terminals 4 and 5 of the black headlight switch connector.

Once the jumper wire is installed, and if the circuits between the headlights and the connector are OK, the headlights should come on.

If the headlights do not come on, then we can assume that there's a problem with the multi-function switch's HI/LO beam selection function or an electrical problem between the connector and the headlights.

OK, this is what you need to do:

1. 1

   Locate female terminals #4 and #5 of the black headlight switch connector (see photo above).

2. 2

   Using a jumper wire, jumper terminals 4 and 5.

3. 3

   The headlights should come on as soon as you jumper the two terminals of the headlight switch's connector.
   
   NOTE: The headlights should come on whether you have the key in the ON or OFF position.

Let's take a look at what your test results mean:

CASE 1: The headlights turned on. So far so good, since this is the correct and expected test result. This test result also tells you that the multi-function switch is OK and that there aren't any electrical wiring problems between the connector and the headlights.

The next step is to test the continuity between pins 4 and 5 of the headlight switch itself. Go to: TEST 6: Testing The Continuity Of The Headlight Circuit.

CASE 2: The headlights DID NOT turn on. This usually indicates a problem with the multi-function switch's LO/HI beam select function.

We can test the multi-function switch without having to replace it by doing a simple multimeter voltage test at fuses 26 and 28 (of the dash panel fuse/relay box). For this test go to: TEST 5: Testing The Multi-Function Switch.

TEST 5: Testing The Multi-Function Switch

Once you jumper together terminals 4 and 5 of the black 7-terminal headlight switch connector, you should have battery power available at fuses 26 and 28 (of the dash panel fuse/relay box).

In certain cases, the multi-function switch (wiper switch) fails and does not allow battery power to pass from the headlight switch to the right and left head-lamps.

So, by checking for power at fuses 26 and 28, we can indirectly test the multi-function switch and find out if it's defective or not.

IMPORTANT: Before you start this test and to get an accurate test result, you need to make sure that fuses 26 and 28 are not blown (see TEST 2).

OK, this is what you need to do:

1. 1

   Jumper terminals 4 and 5 of the black 7-terminal connector as you previously did in TEST 4.

2. 2

   Make sure the multi-function switch is in the LO beam selection.

3. 3

   With your multimeter make sure that fuse 26 and 28 have battery power.
   
   NOTE: You don't have to remove the fuse to test for power. While in place, touch the metal terminal on top of the fuse with the multimeter test lead (the other multimeter test lead must be connected to a good Ground point).

4. 4

   Your multimeter should register 10 to 12 Volts DC if the multi-function switch is functioning correctly.

Let's take a look at what your test results mean:

CASE 1: Fuses 26 and 28 have power. This is the correct and expected test result and confirms that the multi-function switch is OK (and not behind the ‘no low-beam headlights’ problem.

Your next step is to check the continuity of the head-lamp circuit inside the headlight switch itself. For this test go to: TEST 6: Testing The Continuity Of The Headlight Circuit.

CASE 2: Fuses 26 and 28 DO NOT have power. This test result usually confirms that the multi-function switch's LO/HI beam select function is defective (and behind the ‘no low-beam headlights’ problem).