How to fix one side of non-functional turn signals

Halfway on my way home from the dealership I noticed the left turn signals wasn’t working. I probably should have driven right back and have that fixed, but I was more than happy to have left that dealership for good and I was too far out anyway. My car, my responsibility now.

Non-working turn signals are one of the better faults your car can have because it’s pretty simple for everyone to diagnose and fix the error. When I noticed it I had never fixed a turn signal before so that shows how easy it is and you can definitely do that yourself.

It’s actually quite fun to diagnose where a turn signal error is coming from because there are a couple different options and none are particularly hard to fix:

    1. Broken bulbs
    2. Broken fuse
    3. Corroded ground connection
    4. Shorted cable somewhere
    5. Broken relais

The only thing you can’t fix right on the spot with basic tools and maybe a couple hardware store supplies is the relais. It costs roughly 10-20€ to buy a new one and plug it in, but that’s the last thing you want to try. Actually in my case I was pretty sure the relais was okay because one side was working and the hazard flashers had the same error on the left side. The first thing I checked was that the hazard lights showed the same result, you can do that right on the spot from inside the car (or check from the outside to see if the lights flash on both sides).

That meant the most likely cause was the relay itself or a short somewhere.

Before I get back to my error let me talk a bit about the different problems you could have to summarize because I found it hard to find a cumulative list:

  • All signals don’t work:
    • Likely a problem with the relay or a short to ground somewhere. This can also be caused by a broken bulb in some cases.
  • One side (either left/right or front/rear) doesn’t work, but hazard flashers work on both sides:
    • It shows the bulbs and connections are working and the relay is faulty.
  • One side doesn’t work, also doesn’t work when activating the hazards:
    • Most likely caused by a short on that side, check with multimeter to find the cause of the error. Can also be a blown fuse.

In my case I started by checking all the fuses – which were fine – because that is the easiest to test and fix. To check them you simply use a multimeter in resistance / ohm mode and touch the ends of the fuse to get a reading.

Since that wasn’t the problem I next checked the relay. Most of the time you will find the turn signal relay under the steering column or by your main fuse box, but it can also be under the hood, somewhere around the passenger seat and really a lot of places. I face the added complexity of not having a manual and a truck so old that there isn’t much to be found on the internet so I had to find the relay by pulling out relays while the turn signals were on and figuring out which one stopped the working right side.

Once I had pulled it out and put it back in the error suddenly changed and the left side was suddenly working when I activated the flashers. That showed clearly that my relay was faulty, any other cause would not have changed at all.

I wanted to switch it out for the new relay I had ordered, only to find out that even though it was listed as the right part it was a four-pin relay and the one installed was a five pin. I still don’t know what the fifth pin does, but when I took another look at the relay I noticed one of the contacts was oxidized.

Just to test things out I scraped the contact with my knife and put it back in. Lo and behold everything worked again!


I hope this post gives you a general idea on how to deal with non functioning turn signals, it’s really an error you can fix at home and it saves you a great deal of money over going to a mechanic shop.

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