marker lights as turn signals

First let me say hello to everyone. Long time lurker here. I've gotten a ton of extremely useful information from this forum and I am extremely grateful to everyone sharing their knowledge. I finally registered because I can not figure out a solution to my problem.

Second I searched the forums and found quite a few posts, but nothing that seemed to answer my specific question. If I missed it, I apologize.

I have an 04 Mazda 6 that I am trying to get the side marker light to flash with the turn signals. There is a mod posted on the mazda forums that works like this: Cut the ground wire to the marker bulb, splice into the turn signal hot wire and connect it to the ground side of the bulb. This works great, *except* there is a backfeed that lights up the instrument cluster lights on occasion.

The way I understand this mod to work is that when the parking lights are on, the bulb grounds through the turn signal circuit. With the parking lights off, when the turn signals are switched on, the bulb grounds through the parking light circuit. This is where I think my backfeed is coming from. When the marker lights are on, and the turn signals are on, the bulb loses it's ground and shuts off since both sides of the bulb are now high. This is what causes the bulb to have an alternate flash with the parking lights on, yet flash in sync when the parking lights are off. Do I have this correct?

Since the bulb terminals are changing polarity, a simple diode will not work, correct?

So what I tried next is this: I reconnected the marker light ground, cut the positive marker circuit and soldered in 2 1n4001 diodes with both bands on the bulb side of the circuit. I soldered in the marker light positive feed to one diode, and the turn signal feed to the other. This keeps the 2 circuits from backfeeding each other and it works great! Except for one big problem..

When the parking lights are on, and the turn signals are turned on, the bulb does not flash because there is nothing to interrupt the parking lamp circuit.

How do I solve this problem? In other words, how can I interrupt the parking lamp circuit  when the turn signals are on, yet still feed power to the marker lamp when the turn signals are off. Everything that I can think of will end up with the same result - the bulb will not flash whether using relays or diode.

Thank you!

Michael

I found a solution to my problem.

Unfortunately I have to run more wires from inside the car under the hood, but hey it works.

I found a wire coming off the turn signal switch that is constant hot when the turn signals is turned on. This wire leads to the flasher control module which does all the flashing.

Soooo... I still needed the 2 diodes as I had it wired before. I simply inserted a SPDT relay into the circuit wired as follows:

30 - Power feed from marker lights

87a - To non banded side of diode leading to bulb

85 - ground

86 - hot wire from turn signal switch.

So what happens is when the turn signals are turned on, the relay is energized which disconnects the parking light power feed to the bulb. The bulb gets it's power through the turn signal feed wire but will not backfeed due to the diode. When the turn signals are shut off, the relay is de-energized which reconnects the parking light power feed to the bulb illuminating the bulb solid. Again, the diode prevents any back feeds.

Yay for me.

Michael