The article discusses a car side marker modification which enables it to respond to the existing turn signal pulses and flash in tandem with the turn signal flashing. The idea was requested by Mr. Jerry Klein.

Technical Specifications

I have a 1990 automobile which I believe does not have very sophisticated circuitry controlling the direction signals /driving lights and side markers.

This should work in my favor when converting to LEDs.  I am currently using a simple wiring  mod that has worked successfully for 20 years. I cut the side marker's ground wire and reconnected it to the  turning signal lead off the direction signal /driving lights.

The driving lights are dual filament 1157 and the side markers are single filament 158. I love they way they work and would like to convert them with my modification to LEDs.

The side markers flash on when the driving lights are off; they flash off when the driving lights are on.

I quickly realized that this will not work because the light bulbs are working with reversing polarity and therefore I will need a more managed solution.

I think the solution is running the side markers with constant hot lead and controlling the blinking off or blinking on with some kind of control circuit on the side marker's ground.

I would also like to connect up my rear side markers another 158 bulb to the same circuit.

I am not a brain when it comes to circuitry but I have done some simple tasks with relays and am good with a soldering gun.

I wanted to have my 100W  7 amp fog lights work off a dimmer so that I could tune them in to the exact lighting requirements. I purchased a boat dimmer unit that could handle the current which worked with a taping pulse switch for on off and hold for cycling  brightness.

Had I known about your before I could have saved money with your circuit design. Boat parts are synonyms with big bucks.

I can buy the required parts and wire them up as directed. I have looked through your blogs and have not been able to find the exact solution.

Can you please help me with this circuit design and parts list. I would have to know what wire goes to what post on each component.

I could not figure out how to join your blog and therefore this email.The enclosed chart represents the current wiring configuration of my car.

After changing to an LED compatible flashing unit, everything is working correctly.

The chart shows four LED Side Markers they are single function bulbs: off during the daytime; on at night.

They do not blink.The front and rear lights LED bulbs have dual function: two circuits One line controls night / on and a day / off. The other line controls the turn signal blinking function.

We are only concerned with the turn signal function.

I would like the front and rear drivers side LED Markers to blink when the drivers side Front and Rear turn lights are blinking.I would like the front and rear passenger side LED Markers to blink when the passenger side Front and Rear turn lights are blinking.

The project is to create two identical circuits for the car's left and right turn signals.

The circuit taps into the blink turn signal line to determine when it is pulsing causing the car's turning light to blink. The circuit will then blink the corresponding front LED Side Marker.

A wire will be run from the front LED Side Markers to the rear LED Side Markers giving them the same functionality.

During the day, it blinks the LED Side Markers ON.At night, since the LED Side Markers are illuminated the circuit reverses and blinks the LED Side Markers OFF.


The Design 

As per the requirement, the existing side marker lights which are designed to stay ON during night and OFF during day are expected to blink in response to the turn signals lamp switching.

It means the intended customization should be designed such that it blinks the side markers by alternately cutting off the supply during day time, and by alternately applying power during night time, these are two different modes which are required to induce the desired flashing effect on the specified side markers whenever the turn signals are switched ON.

Referring to the diagram, the positive line of the existing side marker needs to be cut and then joined across the two shown points of the recommended circuit.

The design can be understood as follows:

Once the above modification is done, during night, the side marker positive line carrying the positive supply would normally keep the lamp switched ON through the 1N4007 diode, and the N/C contact/pole of the relay.

Now if the turn signal lamp is switched ON, the relay driver BC547 would start pulsing in response to the acquired signals from the turn signal source.

This pulsing would alternately break the positive line of the side marker causing it to blink. The TIP127 in this situation would have no effect on the N/O contact of the relay due to the positive feed at its base from the side marker supply.

However during night time, the positive line of the side marker would have no positive supply, in this situation whenever the relay would be activated in response to the turn signal pulse, the TIP127 also being activated (via base 10k resistor) would pass the positive from the turn signal feed to the side marker via the N/O contact of the blinking relay....this would make sure the side markers yet again blink as proposed in the above request.

Modifying to Flash According to Turn Signals

The following figure shows how to modify the above car side marker further such that it always flashes in accordance with the turn signal pulses:

Circuit Diagram

The 470uF makes sure that the PNP TIP127 remains completely disabled while the turn signal is operating.

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