Rapido on Merc Sprinter

Hello all,
I seem to have a MH that can smell an MOT coming up. Last year all was working well until the day before the test, when last checking, and no brake lights!! Checked all the usual suspects, bulbs, corrosion etc - there are no light fuses in this model, just a box of electronics up under the dash on the left-hand side. No luck so off to the auto spark. He did a temp. fix, and all worked in his yard, but no brake lights by the time I arrived at the test centre - fail. Ended up changing the box of tricks for a s/h unit which worked well.
All was working when parked up for the winter, and we are late starting this year, so usual MOT prep, last check for lights - no rear fog lights!! Usual suspects checked again, nothing found - back to auto spark. He was able to power up the lights with a wire from the battery, but will not work when switched on as normal?? He reckons that the magic electronics box has went on the blink again, as it senses any overloads and shuts down the circuit.
Has anyone out there had similar problems, and can it only be reset by a Merc dealer??
Rest of the van is great, but electrics seem to have a mind of their own.

Best regards, Geoff 'D' (Smiddytheman)

Is there a trailer socket fitted. If so cut it off and wrap each wire individually with insulation tape.
The magic box that you mention, has mini circuit breakers/trip switches instead of fuses, a bit like a household fuse board /breaker box. However these trip switches are very sensitive, even using a standard multi meter across a connection can trip the circuit.
Since it rear lights that is affecting you, remove a trailer socket if fitted, as most are rotten inside.
To reset the system do as fat controller suggested, disconnect the battery for a few moments, reset your trip switches and then reconnect the battery.
Malcolm

Do you mind me ask as to what part of the country that you're from as it would help folks here to direct you towards a merc auto sparky without the main dealer prices.
Malcolm

Got it sorted at last, have been busy, so took a while to get the right person at the right time. Turns out to be a bent over pin on one of the many multi connectors going into the SAMs unit. Seems the pin must have been bent when the multi plug was fitted, and then bent right over when the plug was pushed in. It still was able to make a connection some of the time, and to some of the lights, but was intermittent. The guy who worked on it downloaded a wiring diagram, and then traced back which connector supplied which lamps etc etc. Had checked the rear trailer socket and lamp holders but they were OK. There's a relay box in the rear lamp cluster which supplies the trailer switch, so that the resistance/current in the main circuits remain the same!!
Way too much electronic sh1t...

Thanks for all your reply's...