Flashing LED lights.

Modern cars with complicated wiring systems such as Canbus, can have problems with LED lights. The main problem we have encountered is where all LED lights flash when fitted into the car.

The flashing is caused by a system in the car sending pulses to the lights to check for continuity. By continuity I mean to check that the bulb is fitted and working correctly. If there is a problem then it will give a fault light on the dash. The problem is LED’s are so sensitive that they flash with the test pulses.

We have encountered this problem when a Maypole Plug in system was fitted to a Mercedes. We do understand that this can occur on other vehicles such as the Discovery 3, Iveco and the new Mondeo. We have not yet experienced this problem ourselves with Landrover so we cannot confirm, but the wiring systems for Landrover are also manufactured by RDM Automotive, the same as Maypole systems. If you were to buy a Mercedes wiring system it is called a smart system. This removes the pulses and looks for a load instead, also causing problems with LED lights.

Vehicle specific wiring systems should be fitted due to warranty issues and advanced towing systems, such as fault diagnostic and TSP. However we have found one way to stop your LED lights from flashing is to use a 7 way smart bypass relay. Manufactures of the cars will not recommend this and state that it can invalidate warrantees on electrics on cars if fitted. This is due to the original wiring loom being damaged. We understand that this cannot always be enforced.

We have tried another way, and that is to fit a 7 way smart relay after the dedicated system. This can be done in 2 ways:

1. Fit a second socket on the rear of the vehicle for LED lights, this is run through a smart relay. This can be wired into the back of the existing socket and a power supply can be taken from the battery, meaning that no damage would be caused to the wiring loom on the car.

2. If the vehicle is fitted with a charging socket either as an additional ‘S’ type socket or a fully wired 13 pin socket. Then a smart relay can be fitted to the trailer / caravan, or in a box that plugs into the system.

Please note we have only tried to fit a smart relay to one vehicle with this problem and it did cure all problems. This is only a guide though, and we cannot be held responsible for damage caused to a vehicle by following these instructions.

Update 01/02/2010

We have now had chance to try this on a 2009 discovery 3, the flashing LED indicators were cured.

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