Mercedes Sprinter Faulty Turn Indicators
More often than not the number one cause of indicator problems on the Mercedes Sprinter range is due to the failure of a small control relay located on the lower edge of the fuse board on the steering column. Faults are usually intermittent function of the indicators and hazard warning lamps, ordinarily the indicator will flash two or three times as normal then stop flashing altogether.
Locate the fuse board by removing the plastic panel beneath the steering column, (turn-screw latch at top of cover) at the base of the fuse board you will see a thick red wire connected to a lug terminal this is +12 live constantly, be sure not to short this to the chassis! – look below this and you will see two small relays placed to one side. The relay that is furthest from the thick red wire lug is the indicator control relay (OEM Part is usually grey in colour). Replace this unit and test indicators. The next items to check if this does not cure the problem are the indicator flasher relay module and column control stalk – but nearly always the problem lies with this small control relay.
Just a note: There is no conventional flasher turn signal relay, the one you commonly see as the main plug in unit on other vehicles, that controls the flash rate/duration etc. On the Sprinter the flash module itself is an electronic device and forms an integral part of the fuse control box beneath the steering column and cannot be swapped out without replacing the whole of the fuse board. This is however a very reliable component and is not often known to fail. Read below for further information:
‘’ An electronic wipers, turn signals and engine start control module located within the fuse block beneath the steering column monitors the turn signal circuits and controls the flash rate of the turn signal relay. The instrument cluster continually monitors the right and left turn signal circuits to determine the proper turn signal and hazard warning indicator operation, then flashes the proper turn signal indicators and the contactless relay on and off accordingly. The multi-function switch, the turn signal relay and the left and right turn signal circuits to the instrument cluster can be diagnosed using conventional diagnostic tools and methods. For proper diagnosis of the wipers, turn signals and engine start control module within the fuse block or the instrument cluster circuitry that controls the turn signal indicators and the contactless relay, a Mercedes dealer scan tool is required. Refer to the appropriate diagnostic information.”
For use in fault finding your turn indicator system refer to the circuit/wiring diagram section here.
It’s also worth a mention to check the operation of the hazard light switch on the steering column, if this is not functioning correctly the indicators will not work properly as it forms an integral part of the indicator electrical circuit. Operate the hazard switch several times and check for intermittency.
If you still have problems and have tried all of the above you may begin to suspect the column control stalk, this is an expensive part to replace and you need to be sure before changing this item that it is the probable cause of the issue – try everything else first, it would be a shame to replace this part and then later find it was a £2.00 relay that was the problem.
Good luck !