W202 CDI won't turn over

[Andy_C]

My 2000, W202 CDI auto won't turn over when I turn the key, intermittently, mostly when it has been left for overnight. It just clicks like the battery is flat. The battery is in good condition. All lights on the dash correct: glow plug lamp on for a few seconds, etc.

If I move the gear selector from P to N, it'll sometimes start, just like normal.
Once started it appears to be OK for the rest of the day, until left overnight again.

Any ideas of where to start looking?.

Andy

 

[Stratman]

Turn on the headlamps, then try to start it.

If the lights dim the starter motor is likely to be drawing current but not turning over, so I'd suspect a faulty starter.

If the lights don't dim, I'd be looking at the starter relay and/or solenoid to start with followed by the gear selector lockout.