Strange turn signal behavior when brakes applied

[Masterflex92]

Hi guys,

I have just picked up a 2015 Precedent with a street legal kit already installed.

The brake lights were not working. I started tracing the circuit and found that the relay was not installed behind the switch panel. The cart has an led light kit and a 12v converter, so I linked the grn/wh & blue wires together and everything seem ok. Then I discovered that when the turn signals are flashing and the brake is depressed, the rear light only kind of half blinks. Once the brake light relay times out, the light flashes as normal. The front lights behave normally. Any ideas?

I would appreciate any help you guys can give, This one has got me stumped!

[Fairtax4me]

Most often brake/turn signal lighting problems are due to poor ground connection.
Make sure the negative wire for the lamps is connected back to the main negative at the converter, or to the B- terminal where the converter negative should be connected.

[Masterflex92]

Originally Posted by Fairtax4me

Most often brake/turn signal lighting problems are due to poor ground connection.
Make sure the negative wire for the lamps is connected back to the main negative at the converter, or to the B- terminal where the converter negative should be connected.

I appreciate your reply, I tapped in a separate ground just to be sure, same result. I then removed one of the rear lights and connected an incandescent lamp, same result. This one has got me! I’m thinking it must get the turn signal / relay / flasher harness at this point...

[Briboy]

You may have a bad inverter. I have seen low voltage do strange things to vehicle lighting circuits. If you are using an Inverter, Check it when under load with a multimeter and see if the voltage drops once the load is present.
Or using jumpers, disconnect the current 12v supply and connect to your cars 12v system and see if the behavior continues.
Just a guess...

[Masterflex92]

Originally Posted by Briboy

You may have a bad inverter. I have seen low voltage do strange things to vehicle lighting circuits. If you are using an Inverter, Check it when under load with a multimeter and see if the voltage drops once the load is present.
Or using jumpers, disconnect the current 12v supply and connect to your cars 12v system and see if the behavior continues.
Just a guess...

I have a stable power supply here in my shop, tried it on that too, no joy! Thing is, everything else is working perfectly, nice bright lights etc. Can I post a link from YouTube here?

[Masterflex92]

I have ordered a new turn signal assembly, will report back tomorrow...

[movin-on]

This might be worth a try if the same problem exists when you get your new assembly...It was posted by Sergio a while back...

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.

[Masterflex92]

Originally Posted by movin-on

This might be worth a try if the same problem exists when you get your new assembly...It was posted by Sergio a while back...

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.

So, it was the older style turn signal harness. The new 10LOL one is solid state and worked perfectly off the bat. Interestingly, the new control box features a beeper which sounds when you activate the turn signals, a nice touch!

Thanks for your comments everyone!