How To Test The Headlight Switch (GM 1990-1994)

In this article I'll show you how to test the headlight switch, on your Chevrolet or GMC pickup or SUV, with a multimeter.

You'll be able to troubleshoot a ‘no headlights’ and/or a ‘no parklights’ condition and decisively say that the headlight switch is bad or not the cause of the ‘no headlights’ or ‘no parklights’ problem.

To help you make sure this article applies to your specific Chevrolet or GMC pickup or SUV, this article will help you test the following headlight switch part #'s:

  1. AutoZone Duralast Part # SW932.
  2. AC Delco Part # D1561D.
  3. AirTex, Wells Part # 1S4760.
  4. Standard Motor Products Part # DS647T.
  5. Standard Motor Products Part # DS647.
  6. OEM (Original Engine Management) Part # HLS24.
  7. Wells Part # SW932.

If this headlight switch tutorial does not apply to your GM pickup or SUV, there's one more headlight switch tutorial for 1995 or newer GM pickups that you can find here: How To Test The Headlight Switch (4.3L, 5.0L, 5.7L).

Symptoms Of A Bad Headlight Switch

The most common and the most obvious symptom of a bad headlight switch is that the headlights (headlamps) don't come on when you turn the headlight switch on. You'll also see:

  1. No park lights.
  2. No instrument cluster illumination.

The headlight switch test itself is a pretty simple and straightforward affair and in this article, you'll find the step-by-step testing instructions you'll need to troubleshoot a bad headlight switch.

What Tools Do I Need To Test The Headlight Switch?

Here's a basic list of tools you'll need:

  1. Multimeter.
    1. The multimeter can either be a digital one or an analog one.
    2. If you need to upgrade or buy a multimeter, check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing (found at: easyautodiagnostics.com).
  2. A jumper wire.
    1. Ideally, this jumper wire should have an inline fuse attached to it.
    2. Now, a fused jumper is not necessary since you can use a regular wire as a jumper wire.
  3. Wire piercing probe.
    1. Although this tool is not an absolute must, if you do buy one, you'll realize just how easy it makes testing the voltages inside the wires.
    2. If you need to see what this tool looks like, you can see it here: Wire Piercing Probe.

You'll need basic hand tools to remove the headlight switch from the instrument panel (to gain access to the wires).

Where To Buy The Headlight Switch And Save

You can find the headlight switch in any auto parts store. If you're wanting the buy the original AC Delco headlight switch, you can buy it online for a whole lot cheaper than somewhere local.

The following links will help you comparison shop for the AC Delco and after market headlight switches:

Will the above headlight switch fit your particular GM pickup? Don't worry, once you get to the site they'll make sure it fits (by asking you the specifics of your particular vehicle). If it doesn't fit, they'll find you the right one.

Circuit Descriptions Of The Headlight Switch Connector

How To Test The Headlight Switch (GM 1990-1994)

The headlight switch connector has 7 slots. 2 of those 7 are empty.

In the photo of the connector (in the image viewer), you'll notice that I'm using letters to identify the circuits.

If you take a close look at the bottom of the headlight connector, you'll notice these letters embossed on it.

Throughout the article, I'll be using these exact same letters to aid you in identifying the circuits that you need to test.

These are the circuit descriptions of the headlight and dimmer switch

Headlight Switch Connector Pin Outs
Pin Wire Color Description
A Brown Park Lights, Tail Lights, Radio Illumination, A/C Control Illumination, Convenience Center Illumination
B -- Empty
C Red Battery Voltage Fused Feed
D Yellow Headlight Feed Output
E Orange Park Lamps Battery Fused Feed
F -- Empty


Chevrolet Vehicles:

  • Blazer
    • 1992, 1993, 1994
  • C1500, C2500, C3500 Pickup
    • 1990, 1991, 1992, 1993, 1994
  • C1500, C2500 Suburban
    • 1992, 1993, 1994
  • K1500, K2500, K3500 Pick Up
    • 1990, 1991, 1992, 1993, 1994
  • K1500, K2500 Suburban
    • 1992, 1993, 1994

GMC Vehicles:

  • C1500, C2500, C3500 Pickup
    • 1990, 1991, 1992, 1993, 1994
  • Suburban C1500, C2500
    • 1992, 1993, 1994
  • K1500, K2500, K3500 Pick Up
    • 1990, 1991, 1992, 1993, 1994
  • K1500, K2500 Suburban
    • 1992, 1993, 1994
  • Yukon
    • 1992, 1993, 1994