Tech Tip #1: Relays vs. Resistors

So you’ve been shopping for LED turn signals or an integrated tail light and have noticed this “add relay” option. Or perhaps your bikes’ blinkers are flashing really fast and you’ve seen solutions listed online as “load balancing resistors” or “flasher relay”. Ever wonder what the difference is between the resistors and a relay? We get this question a lot, and now you’ll have the answer.

Here’s the rundown. Most of todays’ sportbikes come with incandescent bulbs for their turn signals. As we’ve all experienced, incandescent bulbs will burn out over time. In order to alert the rider of a blown bulb, the OEM relay will force the bike’s signaling circuit to flash quickly – something we call “hyperflash” (for more info on how a relay works, see this Wikipedia article). There are even some bikes where the turn signal will stay on constantly.

This alerting causes a problem when you want to go with LED turn signals, which are found in our integrated taillights1, pod signals2, and front flushmount signals3. Why do LEDs cause a problem? It’s because they draw very little electrical current when they come on. In fact, it’s close enough to zero current that a bike’s OEM relay can’t distinguish the difference between a functioning LED and a burnt out incandescent bulb, so it goes into hyperflash mode.

1the turn signals are built into an integrated tail light, hence the word “integrated”
2pod signals are aftermarket blinkers that can go on a stock or aftermarket fender/license plate bracket
3we use LEDs in all of our flushmounts, including the TST exclusive HALO-1 lineup

Now that we understand the cause of hyperflash, we can talk about the 2 different ways you could fix it.

Number 1 would be to increase the amount of current the OEM relay sees when the LED signal lights up – an increase that would bring the circuit close to stock levels. That’s where resistors come in.

Number 2 would be to remove the OEM relay and replace it with one that flashes correctly even with LEDs. That’s where, well, the TST Industries relay comes in.

Let’s go more in-depth.

First up is the resistor solution. They get wired into the signaling circuit via a parallel connection, one resistor per LED signal. Without getting too technical, this simply means that the circuit experiences some additional current through the resistors when the LED signal comes on. So there you have it. Install one of these resistors into the circuit near your LED signal and you will increase the amount of current the OEM relay sees when the LED signal lights up (solution number 1). LED signal current + resistor current = incandescent bulb current. A special note to make here: you will (generally) have to wire in one resistor for each incandescent bulb you’re replacing. If you’re changing your front and rear signals (for example, installing flushmounts in the front and an integrated tail light in the rear), you’d most likely need to install 4 resistors in total.

Resistors are included with many of our taillights and some of our other LED products, even if you add a relay to the order (if you add a relay to your order, don’t worry about installing the resistors. There’s no need). Our product ads will normally state whether resistors are included with the purchase of the LED item. If you’re unsure about what’s included, just give us a call or shoot us an email.

Okay, now onto solution number 2: replacing the OEM relay with one that flashes correctly even with LEDs installed. Well, not much to say here other than that’s exactly what the lineup of TST Industries Flasher Relays do! You simply take out the OEM one, plug ours in, and you’re good to go; hence the “plug and play” installation. This setup works for just about every case out there (unless you do something really weird with your turn signals). Not to mention, our relays even allow you to adjust the rate of your flash. Want it a little slower than stock? No problem. Want it just a smidge faster? You got it. All you have to do is turn a dial inside.

We have a few different relays that we manufacture due to the difference in style of OEM relay plugs. Our common ones are RLYG2 with a red female cap and RLYG2F with male plugs and a blue cap. Just navigate to your specific bike category on our website and order the relay that shows up in the product list. You’ll be all set.

Similarities and Differences Between Resistors and a Relay

Feature/Spec Resistors Relay
How it works Increases the amount of current in the signalling circuit to make it look like the LED signal is actually an incandescent bulb to an OEM relay, keeping the OEM relay out of alert mode Replaces OEM relay entirely. Cures hyperflash by not going into alert mode with the low current of LEDs
Automatically included with most tail lights and some LED products? Yes No
Cost Free Under $20
Installation Always wired in the same way. Time depends on comfort level with circuits and wiring Usually 5 minute plug and play deal, can vary from bike to bike
TST exclusive design? No – common across the industry Yes
What should I go with? Go with resistors if you’re on a budget and are comfortable with wiring, or in the rare case that we don’t make a relay for your particular bike. Add a relay to your order if you have the extra bucks to spend and are looking for a simple, one-and-done solution.

Table of Various Signal Setups with Resistor and Relay Notes

Turn Signal(s) Setup – (Front, Rear) Number of Resistors Needed Will replacing the OEM relay with one TST Industries relay work?
Totally stock. Incandescent bulbs in the front and rear. 0 (duh..) Yes
LED signals in the front/mirrors, incandescent in the rear 2 (1 kit) Yes
Incandescent in the front, integrated tail light in the rear (turn signals are a part of the tail light) 2 (1 kit) Yes
Incandescent in the front, LED signals in the rear (what we call LED Pod Signals) 2 (1 kit) Yes
LED signals in both the front and rear (could be an integrated tail light or LED pod signals in the rear) 4 (2 kits) Yes
Having enough turn signals mounted on your bike that you light up the night sky when you signal to turn left You will probably ruin the stock relay anyway… You would also probably ruin a TST Industries relay…
About Erica Nocita

19 thoughts on “Tech Tip #1: Relays vs. Resistors

    1. Hi Charles. In general, you do not. The resistors are made of a ceramic material and can withstand decently high temperatures. That said, I’d recommend mounting them to a metal section of the bike (chassis or tail subframe is common) away from other wires and components if possible. On hot days, in a non-ventilated area, and if you accidentally leave the signals on for prolonged periods, you can find the resistors get way up there in temp. Have you experienced something that seems out of the ordinary?

  1. I have your Integrated tail light as well as your fender eliminator kit along with the relay on my Ninja 300. I would like to add the OEM rear turn signals back on the bike and use that in conjunction with the integrated tail light.

    Question 1: Will the TST relay work with the OEM front and OEM rear turn signals PLUS the TST integrated tail light? When I want to signal a left turn, I want all three lights to blink (front OEM turn signal, rear OEM turn signal and integrated tail light turn signal).

    Question 2: Do you guys have an add-on bracket to attach the OEM turn signals to the license plate holder (fender eliminator)?

    1. Hi Dennis –
      (1) Yes, our relay will work with that combination of lights with zero issues. The only “problem” you may run into is splicing your OEM signals into your bikes plugs.
      (2) Yes, our SKU: PSKMNT ($9.99) can be used to mount the OEM signals onto the bike. However, it is quite an involved process and you can see what needs to be done at the following link. Be sure to fast forward to 16:50 for the process.
      https://www.youtube.com/watch?v=vypjQnCrEgs

  2. Do I have to install the resistors for the LED flush mount signals? Or can I leave them off and plug right into the OEM I have a 2017 fz6r?

    1. Hi Nick! It’s quite tough to really tell if you will need a relay or resistors as every bike tends to have a slightly different reaction to LEDs being installed on the signals. However, I would highly recommend going with our LED Relay as it will work with all stock bulbs, all LEDs, or a mixture of both. It’s completely plug-and-play, fully adjustable, and will even correct and control both front AND rear signals.

  3. I bought the integrated tail lights for my 2016 r6 after installing exactly with the video you guys provided on YouTube, when I turn on and then the fine is running the dashboard light stay on and I have installed the relay and everything is as they should be . I need some answers asap

  4. Hi I bought your halo flush mount turn signals for my YZF-R3 and I’m having a problem now with the opposite turn signal flashing white while the corresponding side is working normally. I have LED switch back light strips installed inside my headlights that are wired to the same turn signal cable on the bike. Is there a solution for this issue?

  5. After experimenting with four flasher/resistors the one that worked has a resistance exactly equal to the total resistance of the two bulbs. Is this an empirical rule ??

    1. Hi Alan – The OEM flasher circuit has a target current draw it likes to see from the signals. There is a threshold value, and once you fall below that value it will flash fast, and some stay solid. If you are changing out one set of OEM signals then you are reducing the current draw on the signaling circuit by only the amount that one of those particular lamps draw. If you replace both front and rear then you are reducing the current draw by two. So if you are trying to get back above the threshold after changing front and rear signals then two resistors will be required in parallel having a value that draws approximately the difference between the OEM signals and OE signals.

  6. Hi, I’m planning on putting aftermarket LED turn lights on the front and an integrated tail light as well on my 2016 Yamaha YZF-R6. will the TST Relay work? will it be the only thing I will need to add? Thank you

  7. Have 2001 Honda 650l and replaced the stock signals with cat eyes led. Using a K & S relay with three prongs and one of which is a ground lead I get nothing and returning the item. Not even a blink…Utube installation!!!
    Would like to replace with one of yours which will plug in. The Honda has a single plastic two female L shape connector. The current stock relay just keeps the lights on with the cat eyes. Do you have one specifically for my bike.

  8. Hi, i already have resistors installed but decided to change to a relay as my hazard lights don’t work with the resistors. I’ve installed the relay but haven’t removed the resistors. Everything works perfectly. Is it okay to leave the resistors AND relay installed or should i remove the resistors? Cheers

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