Technical Electric fault

[Bilbat]

Hi All. One for you to think about. I have a 2005 Fiat Ducato 2.8JTD motorhome which started doing strange things electrically. It started with when driving along and switching the lights on, the engine loses power but if you push the throttle to the floor, it picks up again and runs fine. Three weeks ago while driving early morning to a site in Wales I applied main beam and the radio switched off, change back to dipped beam and the radio came back on. The temerature guage instead of showing a steady normal temp acted a bit like a rev counter, going up when applying power and coming down when not. I have been advised that all of these problems are down to a bad earth on the engine. I have added 2 extra earth straps from the engine to the body and all but one of the faults have gone away. The engine still loses power when I switch the lights on and picks up again when I push the throttle to the floor.
Sorry the description is so long but I wanted to give the whole story.
Anybody got any ideas?
Martin

 

[varesecrazy]

Hi Martin

Is main beam still odd..?

I had that years ago on a ford escort..

A bodged repair had placed the wiring loom against the radiator

Rev counter was robbing power from main beam.. on dip beam no rev counter

Over time I had 7 wires cooked and crispy..

Probably best to investigate before any serious damage occurrs

 

[Crossingkeeper]

Following on from the earth cable suggestion, is the earth connection from the battery to the body clean and tight....I'm musing that the initial current draw from the lights being switched on may be slowing the alternator down instead of being fed from the battery....

I recollect that this is bolted onto the inner wing and can give problems.

I'm reminded of a peculiar fault on my classic Rover where it would only start if I switched the headlights on! I eventually worked out that the current drawn by the lights was 'cleaning up' the dirty starter solenoid connection from which all the other ancillary circuits were fed.

 

[Anthony489]

Hi Bilbat

You seem to have several seemingly unrelated electrical items affecting each other. The logical thing to do in this siuation is to seek a common cause. Any of the wiring from the positive side of the battery up to the point where the various circuits split and go their separate ways is suspect. Likewise any earth connection between engine/gearbox, body and battery negative will carry the current from multiple items.


I seem to recall that these vehicles have a cable which runs from battery negative to engine/gearbox. Part way along is a crimped lug which connects to the body. It's possible for this connection to corrode, so the through path is OK but the "side branch" to the body fails.

I suggest you remove, check, clean and reassemble all the connections to the various cables mentioned above, before looking for anything more obscure. As has been hinted, high current connections can behave in peculiar ways, and vibration, temperature and current can make them come good temporarily before failing again later. Crimped connections can be mechanically sound but inside have a film of corrosion preventing proper contact. The only cure is replacement or by-passing.

 

[Communicator]

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I seem to recall that these vehicles have a cable which runs from battery negative to engine/gearbox. Part way along is a crimped lug which connects to the body. It's possible for this connection to corrode, so the through path is OK but the "side branch" to the body fails.
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As my Ducato is a 2006 2.8JTD, I can confirm the above. The battery -ve cable descends from the battery terminal to the main chassis earth on the inner RHS front wing or wheel arch below the battery tray. At this point there is a "flag" terminal crimped around the conductor, which continues in a duct under the radiator, with the +ve starter cable. The -ve connects to an extended starter motor stud on the clutch housing.

While earthing faults on x244 vehicles do not appear to be as prevalent as on the x250, I fully support the advice given.

The behaviour of the radio and temperature gauge suggests that these devices were seeing a varying voltage. It is my understanding that the temperature sensor for the gauge, is earthed via the engine block. The regulated gauge supply is referenced to chassis, so a poor main earth connection between engine block and chassis, could cause the reported erratic behaviour of the temperature gauge.

On the x244 and probably other versions, the dipped beams remain ON when the main beam is selected. This is contrary to eLearn diagrams, but can easily be verified by observing beam patterns. So when main beam is selected, an extra demand of about 10A is taken from the 90A alternator. Significantly this current will have to flow via the main chassis earth and engine block earth points.

Is the battery negative terminal the original lever operated quick release type with 3 x M6 terminal studs? If it has been replaced by the type which has two screws to clamp the cable, it is worth inspecting carefully.

If the earthing and battery positive connections are OK (I am aware of at least one report of a broken battery positive post clamp), then a remote possibility is a slipping drive belt for the alternator.