How To Test The Turn Signal Switch (Step by Step)

TEST 1: Checking The Turn Signal Fuse Input

To get this show on the road, the first thing I'm gonna' ask you to do, is to verify that the turn signal switch is getting voltage from the turn signal fuse (this fuse is located in the instrument panel fuse box).

The voltage is received on the circuit labeled with the number 2 of the Black turn signal switch connector.

Once this voltage is received (and the hazard switch is in the OFF position), the turn signal switch re-routes battery voltage to the turn signal flasher (we'll test this in TEST 2).

You'll need to disconnect the turn signal switch's connectors to identify the wires you need to test. IMPORTANT: If you haven't already disabled the air bag system, do so now. You can find the instructions here: Disabling the Air Bag System (SIR).

Once you have identified the circuits that need to be tested (we'll be testing a total of 3), make sure you reconnect the turn signal switch connectors to the instrument panel harness connector.

This is what you'll need to do:

1. Locate the turn signal switch's Black connector.
   • Find the circuit labeled with the number 2.
2. Set your multimeter to Volts DC mode.
3. Probe the wire that corresponds to the number 2 with the red multimeter test lead.
   • This is where a wire piercing probe really comes in handy (to see what this tool looks like, click here: Wire Piercing Probe).
4. Ground the black multimeter test lead on a good Ground point.
   • The best way to do this is to use a battery jump start cable to Ground the black multimeter test lead directly to the battery negative (-) terminal.
5. Turn the key to the ON position, since there's battery voltage only with the key in the ON position (also known as the RUN position).
6. Your multimeter will register one of two things: battery voltage (10 to 12 Volts) or no voltage at all.

Let's examine your test results:

CASE 1: 12 Volts are present in circuit 2. So far so good. The next step is t make sure that the turn signal switch is re-directing the voltage to the turn signal flasher. Go to: TEST 2: Checking Flasher Voltage Output.

CASE 2: 12 Volts ARE NOT present in circuit 2. Re-check your connections, make sure you're testing the correct wire and repeat the test.

If your multimeter still does not register battery voltage, then this tells one of three things:

1. That the turn signal fuse is blown and needs to be replaced
2. If the turn signal fuse is OK, then there's a short in the wiring between the turn signal switch and the instrument panel fuse box (although this would be extremely rare).
3. That the turn signal switch itself is not bad, since without this voltage, it won't work.

You'll need to troubleshoot and diagnose this missing voltage before continuing any further.

TEST 2: Checking Flasher Voltage Output

IMPORTANT: If you haven't already disabled the air bag system, do so now. You can find the instructions here: Disabling the Air Bag System (SIR).

In TEST 1, you checked and confirmed that the turn signal switch is getting power from its fuse in the instrument panel fuse box.

The next step is to check and confirm that the turn signal switch is re-routing battery voltage to the turn signal flasher.

The circuit (wire) that sends this voltage to the flasher is the one that's labeled with the number 3 of the black turn signal connector.

OK, this is what you'll need to do:

1. Identify the circuit labeled with the number 3 of the black connector.
   • The black connector must remain connected to the instrument panel harness connector at all times during this test.
2. Turn the ignition switch to the ON position.
3. With your multimeter to Volts DC mode:
   • Probe the wire that corresponds to the number 3 with the red multimeter test lead.
     • A wire piercing probe is the best tool for this job (To see what this tool looks like, click here: Wire Piercing Probe).
4. Ground the black multimeter test lead on a good Ground point.
   • Use a battery jump start cable (if you have one) to Ground the black multimeter test lead directly to the battery negative (-) terminal.
5. Your multimeter should register battery voltage (in the range of 10 to 12 Volts DC).

Let's examine your test results:

CASE 1: Battery voltage (10 to 12 Volts) was present. This is the normal and expected test result. The next step is to go to TEST 3: Flasher Voltage Input.

CASE 2: Battery voltage (10 to 12 Volts) WAS NOT present. Make sure that the hazard light switch is not activated, re-check all of your multimeter connections and repeat the test one more time.

If your multimeter still did not register any voltage (with the key in the ON position), then the turn signal switch is bad and needs to be replaced.