HELLA warning on starter motor problem cause

With the cooler months ahead set to place more stress on starter motors, HELLA is reminding technicians of the need to diagnose faults carefully.

The risks of jumping to the wrong conclusions are starkly illustrated by frequent starter motor failures for 2008 onwards Renault Masters fitted with 2.0 dCi M9T or M9R engines. The same problem has also afflicted the Renault Traffic, Nissan Primastar and even the Qashqai.

“The vehicle will present in the workshop with a failed starter motor,” said Ian Mattacola, Product and Brand Manager at HELLA. “Unfortunately, if you simply fit a replacement without properly investigating and looking out for some tell-tale signs, then you can soon be faced with the headache of the new part failing quickly as well.”

Such situations become notoriously problematic – leaving drivers inconvenienced, garages potentially facing a financial hit and suppliers managing labour-intensive warranty claims processes, which will ultimately be rejected. To avoid this, HELLA’s starter motor installation instructions recommend several vital pre-fitment steps. Amongst them is a check of the ignition switch, to ensure it moves freely and easily between positions.

HELLA’s technical team says starter motors for these vehicles often fail due to excess load because the ignition switch ‘sticks’ leaving the starter motor engaged for too long. This ‘sticking’ can be caused by ageing electrical switch mechanisms being slower to disengage or more often by a broken or weakened mechanical spring failing to return the ignition switch back to the initial position as it should.

When the starter motor remains engaged like this whilst the engine is running, for even short periods of time, the load and resulting heat can quickly burn-out the motor. Careful assessment of the failed unit is essential; look out for blue discolouration around the armature shaft – caused by excess heat, or signs of a milled pinion – resulting from high-speed rotation.

If such damage is found, then the ignition switch is the likely culprit. However, it’s important to be aware that extended starter motor running may also be caused by poor engine starting. Also, even if the failed starter motor does not obviously show these signs, technicians should still check electrical connections for any corrosion as well as the ring gear on the engine flywheel for signs of damage.

“Garages must take the time to look carefully for signs of failure through over-speeding when replacing starter motors,” said Ian. “Where this is the suspected cause, it may to be important to either advise customers to replace the ignition barrel and switch assembly, or clearly explain the risks of not doing so lie with them.

“This way, if they do decide to ‘chance it’ by only changing the starter motor, the garage is protected if a repeat failure later occurs.”

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