pre engaged fixed drive.take the motor to a motor factors for reconditioning,most likely to be mechanical failure rather than brushes.when you remove the motor you can check the extent of wear by checking for end float.grab hold of the pinion and push and pull.
ozone
November 2011
Starter solonoid sticking, (thats the bit on top of or on side of starter motor) take it out, and clean the inside and arm.
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Try fixfault.com to fix caravans/motorhomes.