12 63 520 Replacing master relay (M51, M52, M62)

Switch off ignition.

Fold open locking bracket (1).

Remove rubber gasket (2).

Fig 1: Removing Rubber Gasket

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Remove retaining clip (3).

Pull filter housing (4) upwards to remove.

Fig 2: Pulling Filter Housing Upwards

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Unscrew bolts (1).

Fig 3: Identifying Bolts

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M52, M62:

Fig 4: Identifying Master Relay In Digital Motor Electronics

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Notes on troubleshooting:

If the starter cranks the engine during the starting sequence but the engine fails to fire, check the engine fuses and, if necessary, replace them entirely along with the fuse holder.
Search for cause of melting of fuses.