Turn Signal Troubleshooting

Turn Signal Troubleshooting Kopycinskis Brain Signal Socket

1. This a typical dual filament signal socket used for decades before the conversion to bayonet-style bulbs. There are two metallic buttons on the bottom of the bulb that mate to the two metal tabs at the bottom of the socket (red arrows). Each connection services one of the two bulb filaments. The metal base of the bulb is also connected as a ground to the bulb filaments and the side tab in the socket (black arrow) is the ground connection on the socket.

1. This a typical dual filament signal socket used for decades before the conversion to ba

Sometimes it's the simplest things that cause us the greatest consternation. One of those simple things is the lighting on our vehicles. Vehicle marker signals (running, brake, turn, etc.) use either a socket for a single filament or a dual filament bulb. A single filament bulb will have one contact on the bottom of its base while a dual filament bulb will have two contacts.

When troubleshooting a bulb that's not working you may find that it's not simply a failed bulb that's the problem. As vehicles age, their electrical connections corrode and can eventually turn intermittent, or fail altogether. The corrosion or oxidation layer that forms over time is a non-conductive substance that can stop the flow of current across the bulb and socket contact point. Sometimes you may find the contacts are charred or thermally damaged.

Once you've swapped bulbs or confirmed that your bulb is good, it's time to look deeper. Remove the bulb from the socket and look at the contacts inside the socket.

These contacts can be cleaned with a bit of sandpaper or steel wool to restore a shiny surface to make connection with the bulb. If this works, you're good to go. Otherwise, it may be time to pull out a voltmeter to check for voltage at the socket contacts. It's also not uncommon to have a ground connection problem, and this can be suspect when neither filament lights. You can check this by running a jumper wire from the metallic bulb base to a good chassis ground.
These contacts can be cleaned with a bit of sandpaper or steel wool to restore a shiny sur
2. A small dab of dielectric grease on the contacts will help prevent the recurrence of oxidation, especially in humid areas where it's more likely to occur. A light coating on the bulb base will also help stop the bulb from sticking in the socket over time.
2. A small dab of dielectric grease on the contacts will help prevent the recurrence of ox
3. When all else fails with checking the harness voltages and cleaning your existing socket, it's possible to pick up a replacement at most any auto parts store for just a few bucks. You'll need to cut the wires to your old socket and determine which wire is which before crimping the harness wires to the new socket wiring. Check the bulb operation against the one on the other side of the vehicle to determine which condition should energize the brighter of the two filaments. Other problems could lie further upstream in the vehicle harness, but the majority of problems typically occur at the bulb socket.
3. When all else fails with checking the harness voltages and cleaning your existing socke