A universal turn-signal relay

It will works with any indicator type, from LEDs to 21W standard bulbs, no matter the bulb wattage, with the right frequency without the need for a resistor. When built with care & protected from moisture this design is much more reliable than the classical relay system.

This circuit is designed to replace directly the original turn-signal relay. It uses the same two wires connection. It only lacks the ability to warn the driver when a bulb fails like standard relays.

Schematic & Design



All parts are very common and cheap : overall cost should be less than 5€.
• All resistors are 5% 1/4W.
• The variable resistor allows to precisely tune the blinking frequency at 85/min.
• Integrated circuit : NE555 or equivalent.
• Diode : 1N4001 or equivalent.
• All capacitors should be rated at 25V min or (better) 50V.
• The power transistor IRFZ43N is capable of currents up to 26A, which is far above what is required by the four indicators : 7A for 21W x 4 bulbs. A BUZ71 may be used instead the IRFZ34 or any power MOSFET equivalent. No heat sink is required.


(image)The turn-signal relay on a TDM900 is located under the fuel tank - see pic below (click to enlarge) :
• Pin (A) goes to the Brown/Green wire (+12V side)
• Pin (B) goes to the Brown/White wire (turn-signal switch side).

(image)clear LED indicators.

Another circuit (taken from a well-known magazine)


This circuit is a personal design, use it under your own responsibility.


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