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

TEST 7: Rear Left Turn Signal 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).

This section of the article will help to check that the turn signal switch is activating the Rear Left turn signal lamps.

Like all of the previous tests, you'll be using your multimeter to check for DC voltage in the appropriate circuit (wire).

The circuit that you'll be testing is the one labeled with the number 7 of the gray turn signal switch connector.

This is what you'll need to do:

1. Locate the circuit labeled with the number 7 of the turn signal switch's gray connector.
   • Remember, the gray connector has to remain connected to the instrument panel harness during the 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 7 with the red multimeter test lead.
   • Remember, you'll be probing the wire somewhere between the gray connector and the turn signal switch.
4. Ground the black multimeter test lead on a good Ground point.
5. Activate the left turn signal.
6. You're multimeter will register one of two things:
   • A battery voltage (10 to 12 Volts) that flashes ON and OFF.
   • No battery voltage at all.
7. When done, turn the turn signal and ignition switch off.

Let's examine your test results:

CASE 1: The multimeter registered 12 Volts. This tells you that the turn signal switch is activating the rear left turn signal lamps.

If all the following tests passed with flying colors, you can eliminate the turn signal as bad:

• TEST 1: Checking The Turn Signal Fuse Input.
• TEST 2: Checking Flasher Voltage Output.
• TEST 3: Flasher Voltage Input.
• TEST 4: Front Right Turn Signal Output.
• TEST 5: Rear Right Turn Signal Output.
• TEST 6: Front Left Turn Signal Output.

CASE 2: The multimeter DID NOT register 12 Volts. Re-check your connections making sure that you're testing the correct wire of the correct turn signal switch connector, and repeat the test.

If your multimeter still does not register any voltage, then the circuit inside the turn signal switch that activates the rear left turn signal lamps is bad, which of course means that you've got a bad turn signal switch on your hands.

Test Summary

There are so many ways that you can test the turn signal switch, I've presented my way of doing it and hopefully it helped you to solve the 'No Turn Signals' problem.

I know that this article has been very narrow in its focus since it only tests the turn signal switch and nothing else, so if you would like to add any info (for the benefit of anyone else with a similar problem or symptom) please feel free to share your diagnostic and repair experience. You can use the contact form below:

Feel free to also check out all of the 'How To Test' article found here:

• GM 4.3L, 5.0L, 5.7L Index Of Articles.