My uncle has a camper van based on a 2000 Peugeot Boxer 1.9TD. When he starts the engine, sparks are visible from the earth strap between the chassis rail and the gearbox housing.
I suspect it would make better sense, rather than just clean up all the contacts, to replace the strap.
Does anyone know a good source for earth straps, and how to test them. I suspect a reasonable test would be the electrical resistance of the strap but don't know what sort of figure would be normal.
Edited by Dynamic Dave on 27/05/2008 at 14:39
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If you clean the contacts, and tighten the bolts, as long as there's less than 0.2 volts dropped btween the engine and body during cranking, then, it's OK.
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Thanx, number cruncher, invaluable advice.
I will get to work on it tomorrow.
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Not only clean but also run another lead from the battery direct to the engine as a second earth;ready made leads of all lengths are normally available at accessory shops and Halfords.
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dr chris
Very common problem on these. The braided-copper earth strap ends in a stainless wrap - held by a steel bolt, into aluminium, right on the bottom of the box, exposed to salt.... The words "dissimilar metal corrosion" obviously do not translate into French.
You'll find that the bolt head has blasted it's way right through the stainless plate. It may be near-impossible to remove - if so; cut the strap and leave it.
Acquire a commercial-sized earth strap [the meatier the better] from somewhere like LSUK and fix it from the battery earth point on the R/H wing across to a handy bolt-hole on the front end of the head. A spot of terminal grease or Vaseline on both ends and you won't need to go there again.
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The earth strap connection to the gearbox was not as badly damaged as it might have been, so I was able to clean everything up. I then improved on my uncle's installation of the wiring to the battery he had recently installed.
Apparently the van now starts almost immediately whereas before it had to be cranked for a long time. In addition, no more sparking from the earth strap.
However, as this problem will recur and probably cause a breakdown somewhere in the depths of Europe, I plan to put in an additional earth as suggested as a fail safe, since it wont cost a fortune.
Thanx to all for the advice.
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As an aside, I'm a great believer in Copper-based grease for all sorts of reasons. In this case I used it on the bolts holding the earth strap to prevent them seizing in the future. However, does this grease contain enough Copper to increase electrical conductivity in such a situation or do the other ingredients of the grease negate any such effect?
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dr chris
Anything is better than white rust; so overall, it's definitely going to be a benefit.
Copper grease comes in many different forms. The most common one years ago was Copaslip; which is a mix of zinc and copper particles in a bentone clay base for high temp performance. Some of the later products can be based on anything, including hydrocarbon oils.
One of the best ways to ensure a good electrical contact is the use of toothed [shake-proof] washers. The better ones are vicious things that, when tightened, bite into the surfaces and provide multiple metal-to-metal pathways - not something easy to achieve with two flat surfaces, particularly if previously corroded.
Contact grease [often sold as battery terminal grease] is probably the optimum for joints that are not too exposed to salt-spray.
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