Turn signal flashing on both sides

[Swervdriver]

The turn signals on my ‘06 Precedent flash on both sides when either turn signal is turned on. The correct side flashes brighter than the off side, and it is less noticeable when headlights are turned on. I have checked all connections for loose or corroded wires and come up clueless.

[Sergio]

That is typically an issue with rear LED lights as some units share a common driver between the marker-lights and the brake/turn lights.

If You have an LED headlight you may also notice a dim light when the lights are OFF and the brake pedal is pressed.

The solution is to wire a diode in each tail light on the "marker" wire (not the brighter brake/turn wire).

The diode should be oriented with the cathode (side with the stripe) towards the rear light assembly.

You can use a regular 1N4001 through 1N4007 series diodes.

[Swervdriver]

Thanks for the tip. I do have the issue of the headlight blinking dimly when turn signal is on, even without brake applied. Should a diode be wired in on all 4 turn lights?

[Sergio]

Typically the issue is only on the rear lights as they have two different brightness circuits that share common component paths.

Since the turn signals are isolated side to side by the turn signal assembly, there is no need for a diode.

The headlight/"marker-lights" circuit is the issue since they are all connected together so when you turn the left or right side turn-signal, current goes out of the "marker-light" wire into the other marker-lights and the headlight.

Adding a diode to the +12v wire that powers the marker light in each rear assembly will fix the issue as it will prevent current from back-feeding the rest of the marker-lights.

[Swervdriver]

Ok! Thanks again!

[Swervdriver]

When I checked the plug after disconnecting tailight, all 3 wires are hot at all times reading what I assume is pack voltage.lights are not wired like a car because of no ground but I don’t understand why they are hot without having lights on. The diode did seem to stop the back feed to other lights, but somehow seems dimmer.

[Sergio]

How are you measuring the voltage, meaning where are you placing the meter probes?

The typical colors are:

Black - Negative
Brown - Running Lights +12v (diode goes here with the "Stripe" towards the rear light)
Red - Brake/Turn signal light +12v (this wire can have other colors: White or Yellow)

If You did not unplug both rear lights remember that pressing the brake will cause the other rear light to back feed into the running lights power wire.

With just the headlights ON, You should get +12v between Black and Brown.

[Swervdriver]

I held the neg probe on the neg side of battery while checking each wire on the light plug. You say the black wire on the plug should be a ground?

[Sergio]

Yes the Black wire should be the negative.

Measure the voltage from Pack negative to the Black wire, what is the exact voltage reading You are getting?

Measure the voltage between the pack negative and the Brown wire, what is the exact voltage with the Headlights OFF and with the Headlights ON?

I am assuming You have a 48v->12v converter and are not just tapping some of the batteries for 12v.

[Swervdriver]

I think what I had done was ground the meter on the wrong battery, giving me a 36v reading on all wires. On the pack neg to the right rear running light I get 12.1v. If I want to install turn indicator lights on my dash, do I have to wire them from the lights or from the flasher?