Ack'sFAQ: How Automotive Turn Signal Modules (Mechanical and Electronic)and ballast Resistors Work

How Mechanical, Electronic Turn Signal relays and Ballast Resistors Work

There are two basic types of user-replaceable turn signal relays - Mechanical and Electronic. Ballast resistors can be used to "fix" fast flashing when using LED lamps with a mechanical Relay. More on this topic will be presented later in this article.

Mechanical Turn Signal Relay

Mechancal turn signal relays work using a bimetal reed switch with a small heater element that runs the signal lights in a regular on-off sequence. The bimetal reed inside the relay is a thin piece of two different metals that are sandwiched togther. When heat is applied to the bimetal reed using the heater element, the two metals expand at different speeds causing the reed to bend or warp.

This motion causes the electrical contacts to close inside the turn signal relay which causes the turn signal lights to turn on.

When the lights turn on, the turn signal circuit now has two paths for the electricity to travel through - the the heater element and the turn signal lights. Because the turn signal lights provide a better path to ground, the heater element cools causing the bimetal reed to cool until the bimetal reed switch opens.

The open switch disconnects the current flow path to the lights causing the heater element to reheat the bimetal reed which turns on the turn signal lights on again. The On-Off cycle repeats until the steering wheel switch mechanism or the operator interupts the process.

Here is a looping graphic animation of how the sequence works:

Notice that the flash rate became faster when a filament bulb was replaced with a LED bulb in the graphic. This is because the LED bulb draws less current than the the filament bulb it replaced. Because of the change in current running through lighting part of the circuit, the bimetallic switch cools down faster causing it open sooner. This makes the turn signal lights blink faster.

You can Google "Ohm's Law" to learn more about the relationship between voltage, current and resistance in electrical circuits.

Electronic Turn Signal Relay

Electronic turn signal relays do the same thing. The main difference is it uses an electronic circuit instead of a mechanical switch to create the flashing action.

The electronic turn signal module contains a digital "flip-flop" circuit that generate a steady stream of perfectly-timed pluses. A power transistor boosts the output of the flip-flop circuit so it can power the turn signal lamps. A miniature speaker is also included in the turn signal unit to provide the traditional "clicking" sound.

Here is an animation of the electronic flasher in action.

Note that the electronic turn signal flasher delievers precise string of flip-flop pulses which allows Bulb and LED lamps flash at the same rate in any combination.

Revision Edit

After further examination of electronic flasher construction, I found that nearly all electronic flashers are equipped with a relay instead of a power transistor to boost the power output of the flasher. Here is a schematic depiction of a relay-driven electronic flasher module:

Resistor Ballasts

Resistor ballasts can be wired in series with LED lamps when using a mechanical turn signal relay.

But there is a problem with this method:

The Novita/Tridon EP34 turn signal module is the electronic equivalent of the Original Equipment Manufacturer (OEM) turn signal module`for the Suzuki Samurai. It is also important to point out that the Samurai turn singal module follows the Japan Organization of Standards (JSO) for the pinouts of this device. It shoud not be confused with the Internatioal Standards Organization (ISO) pinout used by North American vehicle manufacturers.

The reason why I mention this is the fact that there is a ISO turn signal module that looks EXACTLY like the JSO turn signal module used in the Suzuki Samurai. The difference is that the positive terminal is switched with the negative terminal on the two different modules. If you plug an ISO ELECTRONIC turn signal module into a Samurai, you will destroy the ISO module the first time you use your turn signal.

ALWAYS purchase a JSO electronic turn signal module - like the Tridon/Novita EP34 - for your Samurai.

NEVER purchase an ISO electronic turn signal module - like the Tridon/Novita EP35 - for your Samurai NO MATTER WHAT THE AUTO PARTS COUNTER PERSON SAYS!

i hope that this helps!