General wiper stopping 2007 fiat ducato

[jimmybrad]

ive ordered more earth straps

 

[Communicator]

You will need specialist equipment to measure the earth strap resistance, as measurement of such small resistance is beyond the capability of a simple multimeter.

After cleaning the mating faces, a smear of vaseline or other thick grease, will help to exclude moisture and hence future corrosion.

Connections must be tight.

 

[jimmybrad]

hopefully ive an electrician on thursday thats going to have a looksee ill let you know what he finds

 

[Anthony489]

Hi

The symptom of increased idle RPM is due to the ECU trying to compensate for a low battery voltage/insufficient charging. A bad/intermittent connection anywhere in the charging circuit can be the cause of this, and the engine to body earth strap forms one part of this circuit. I suggest you (or your electrician) systematically check all the connections in the charging circuit, including the earth returns.

The problem with the braided earth strap is that it relies on lots of parallel strands all working together. When the strap is new, all these strands are clean and touching each other. As the strap ages (it's fairly exposed) the strands tarnish. Tarnish also builds up between the strands and the inside of the crimped end lugs. Effectively, you end up with only a small percentage of the strands carrying current and the rest insulated by tarnish. A new strap has a resistance of about 0.001 ohms (one thousandth of an ohm). A failed one might be 0.02 ohms, and if the alternator pushes 50 amps through it there will be a 1 volt drop. However, any bad connection with high resistance can be rather unstable, and change with moisture heat, vibration etc. You can clean the terminals and the visible faces of the lugs, but it's impossible to clean the inside of the lugs which is why I recommend binning the strap and fitting new. There's no problem with fitting extra straps, either piggy backed onto the same fixing studs or placed somewhere different. Ideally, keep their length short, say less than 300 mm.

I attach schematics of the charging circuit

 

[Communicator]

I would like to start by offering a little clarification to the excellent contribution above by @Anthony489.
It is inside the crimped ends of the strap, where current transfer between strands is critical. I would not expect any other significant current transfer between strands along the length of the strap.

Allan Evans, the now deceased proprietor of aandncaravanservices, was one of the first people to publicise this problem, but the posting was possibly on another forum. If I remenber correctly, Allan sectioned a crimp on a faulty strap and reported finding corrosion within the crimp as Anthony has suggested.

At the risk of repeating myself, I think that the best way to prevent, or at least delay the onset of such corrosion is the application of protective grease to exclude moisture, not only to the joint faces but to the the conductor at both ends of the crimps. I have done this to the different earthing arrangement on my x244.

 

[nigelvan]

Hi

The symptom of increased idle RPM is due to the ECU trying to compensate for a low battery voltage/insufficient charging. A bad/intermittent connection anywhere in the charging circuit can be the cause of this, and the engine to body earth strap forms one part of this circuit. I suggest you (or your electrician) systematically check all the connections in the charging circuit, including the earth returns.

The problem with the braided earth strap is that it relies on lots of parallel strands all working together. When the strap is new, all these strands are clean and touching each other. As the strap ages (it's fairly exposed) the strands tarnish. Tarnish also builds up between the strands and the inside of the crimped end lugs. Effectively, you end up with only a small percentage of the strands carrying current and the rest insulated by tarnish. A new strap has a resistance of about 0.001 ohms (one thousandth of an ohm). A failed one might be 0.02 ohms, and if the alternator pushes 50 amps through it there will be a 1 volt drop. However, any bad connection with high resistance can be rather unstable, and change with moisture heat, vibration etc. You can clean the terminals and the visible faces of the lugs, but it's impossible to clean the inside of the lugs which is why I recommend binning the strap and fitting new. There's no problem with fitting extra straps, either piggy backed onto the same fixing studs or placed somewhere different. Ideally, keep their length short, say less than 300 mm.

I attach schematics of the charging circuit

Anthony, where do you get these schematics? They are very useful (I'm still looking to make a D+ connection for my DC-DC charger). Are they from eLearn?

About the strap: Wouldn't it be better to replace is with a proper insulated >10mm2 cable? As far as my electronics background take me, so many strands only offer advantage in high frequency situations where Eddy currents starts playing a role. With DC this seems not the case.

 

[jimmybrad]

hi
just want update everyone, bought second hand BCM , tried it in van, all symbols on dash but had lock on dash, engine turned over but wouldnt start,sent both BCMs away to Dash Master for cloning, on return fitted secondhand cloned BCM no light on at all on dash apart from engine light and a red steering wheel.Dash Master said they hadn't come across this before but no other help, thought id try original BCM and all was well, everything working as it should, went up to lake district last week and all ok, talking to a mechanic and he said he had a similar problem with a peugeot boxer 5 years ago and he sent the BCM away for cloning and the technician said he comes across this problem from time to time and thought it may be down to dampness and suggested putting those silicon gel bags on the dash that take moisture out of the air,i thought that he may have a point as my van had hardly moved for 18 months and when i started with the problem kept the BCM indoors for a couple of weeks whilst i tried to sort things out so maybe dried out. anyway things seem to be working but im on pins waiting for it to happen again,away again next week so think positive. thankyou everyone for your help and suggestions and how do i donate to the site. will keep updating.
regards
jim bradley

 

[Communicator]

Anthony, where do you get these schematics? They are very useful (I'm still looking to make a D+ connection for my DC-DC charger). Are they from eLearn?

About the strap: Wouldn't it be better to replace is with a proper insulated >10mm2 cable? As far as my electronics background take me, so many strands only offer advantage in high frequency situations where Eddy currents starts playing a role. With DC this seems not the case.

As Anthony perhaps did not see the question about the schematics that he posted, may I confirm that they will have been sourced from eLearn, but any added notes and wire colour translations will be his own.

Regarding the construction of the earth strap, the use of muliple fine strands will have been in order to increase flexibility, and hence reduce the possibility of mechanical failure that could be caused by engine vibtation.

 

[chris3234]

As Anthony perhaps did not see the question about the schematics that he posted, may I confirm that they will have been sourced from eLearn, but any added notes and wire colour translations will be his own.

Regarding the construction of the earth strap, the use of muliple fine strands will have been in order to increase flexibility, and hence reduce the possibility of mechanical failure that could be caused by engine vibtation.

Seems to didn't think it was that needed as fiat fitted normal insulated earth straps to several models of 500

 

[jimmybrad]

happy new year to everyone, just an update, van still working ok with original BCM,been up to lake district twice and all was well, i then went upto lakes just before exmas when the freezing weather was on and engine would not attempt to turn over, all dash symbols on but absolutely no click or anything when trying to start, switched on off several times and it started, same happened whilst in the lakes, i decided to direct a small fan heater to the front of cab for several hours and the engine started no problems, came home and had to leave van on side of road due to ice, tried the day after and van would not start,when the thaw came tried van and it started straight away, im still running a dehumidifier under pedals next to BCM.
regards
Jim Bradley