How To Test The Headlight Switch (1994-1997 Chevy S10 And GMC Sonoma)

This tutorial will explain how to test the headlight switch on your 1994-1997 Chevrolet S10 (GMC Sonoma).

We'll test the headlamp and park-lamp circuits of the headlight switch.

When the headlight switch fails, the headlights won't come on.

NOTE: This tutorial applies to both the 2.2L and 4.3L equipped S10 and Sonoma (1994-1997), since they all use the same headlight switch.

Contents of this tutorial at a glance:

  1. Headlight Switch Basics.
  2. TEST 1: Testing The Continuity Of The Headlight Switch.
  3. TEST 2: Bypassing The Headlight Switch.
  4. Where To Buy The Headlight Switch.
  5. More 2.2L GM Tutorials.

Headlight Switch Basics

How To Test The Headlight Switch (1994-1997 Chevy S10 And GMC Sonoma)

The headlight switch is a simple on/off switch that can be easily tested with a multimeter and by bypassing it (with a jumper wire).

Although the headlight switch has 6 male spade terminals, its connector has wires for only 4 of them.

When it fails, you'll see a ‘no headlights’ and/or ‘no park-lights’ condition.

TEST 1: Testing The Continuity Of The Headlight Switch

Testing The Continuity Of The Headlamps Circuit. How To Test The Headlight Switch (1994-1997 Chevy S10 And GMC Sonoma) Headlamp Circuit Diagram Of The Headlamp Switch. How To Test The Headlight Switch (1994-1997 Chevy S10 And GMC Sonoma)

To get our headlight switch diagnostic under way, we're gonna' test the continuity of the headlights and park-lights circuits (inside the switch) with a multimeter.

The two park-light switch terminals that we're gonna' test are male spade terminals A and E.

The two headlight switch terminals that we're gonna' test are male spade terminals C and D.

The illustrations in the image viewer above will help you identify them.

Let's get started:

  1. 1

    Remove the headlight switch and place your multimeter in Ohms mode.

  2. 2

    With the park-lights switch in its OFF position your multimeter should read NO continuity on male terminals A and E.

    Your digital multimeter will display the letter OL if there's no continuity.

  3. 3

    With the headlight switch in its OFF position your multimeter should read NO continuity on male terminals C and D.

    Your digital multimeter will display the letter OL if there's no continuity.

  4. 4

    With the park-lights switch in its ON position your multimeter should read continuity on male terminals A and E.

    Continuity means any resistance value that is not the letter OL on your multimeter's display. The known-good headlight switches I've tested have given an Ohms reading between 1 mega-Ohm to 500 Ohms when continuity is present.

  5. 5

    With the headlight switch in its ON position your multimeter should read continuity on male terminals C and D.

    Continuity means any resistance value that is not the letter OL on your multimeter's display. The known-good headlight switches I've tested have given an Ohms reading between 1 mega-Ohm to 500 Ohms when continuity is present.

Let's analyze your multimeter continuity test result:

CASE 1: Continuity exists in the indicated terminals when you turn “on” the headlight switch. This is the correct and expected test result.

For the most part, a continuity reading tells you that the headlight switch IS NOT defective. But to be sure, I recommend going on to the next test: TEST 2: Bypassing The Headlight Switch.

CASE 2: Continuity DOES NOT exist in the indicated terminals when you turn “on” the headlight switch. This test result almost always means that the headlight switch is defective.

To be sure, I suggest doing one more test and it's to bypass the switch itself. For this test go to: TEST 2: Bypassing The Headlight Switch.