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Direct Starter Earth Cable


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My starter motor clatters rather than engages. I have improved things greatly by looking at all the earths but this morning in the real cold it clattered again.

Am I right in thinking that a direct earth cable from battery to starter is only beneficial if not required.

I have read about 10 16 and 40 cable being used.......... is 16 safely adequate.

And how long should I get to comfortably do the trick.

That reminds me to ask where should I attach the cable to exactly so I know where to aim for. Obviously I guessed the battery end!

Thank you all

Edit - I notice that a previous topic below covers this mostly so sorry for the repetition, I just need to clarify it all as there is some confusion.

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eds, good to see you back!, My earth on my starter motor(200 tdi defender) is attached to the rear of the unit (opposite end to where the unit attaches with the 3 bolt's onto the flywheel housing) via a stud affair thing that is, then the earth cable is attached to the block then goes onto the chassis-however if you do not have the stud thing on your starter motor I have seen the earth mounted onto where the 17mm bolt goes into the flywheel housing on my ex's 300 TDI disco-this then earthed the unit out so it would have the same effect as the stud if you follow what I mean?

I'd also be interested in what size/length the cable should be for what you want to use it for, as I was thinking of doing the same-even though my earth is attached to the starter as I typed above I would like to have a couple more earth's on my truck and this is one of the one's I was thinking of doing

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Hey John

Thanks for the info as usual!

So far I have concluded the cable should be 16mm2 - about 30 inches in length and attached to the bolt on the back of the starter..........

I am hoping a pro comes along and confirms all this!


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16mm is a little small I'd say, generally only rated to around 110 amps or so (although obviously this depends on the cable). I would go for 35mm cable which should be good for around 240A.

25mm would 'probably' be okay, but best to be on the 'belt and braces' side of it with this sort of thing.


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I have just ordered 2m of 40 mm2 starter cable to do just this over the weekend.

The starter I have on my 300 tdi does not have an earthring bolt on the rear of the unit so will have to use the mounting bolt and then take it all the way back into the battery box. Have managed to borrow a good crimpin device and plan to also not rely on the crimp to the chassis halfway down the current main negative lead from battery yo gearbox housing. Pretty sure this crimp is responsible for much of the reluctant starting. So will add new earth from gearbox housing to chassis instead.

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Not sure if tinned or untinned cable is better for a defender. Tinned sounds better but I don't think anything is tinned normally.

Does anyone know the amps expected and whether I should replace the positive too.

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