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MPV Section - Forums for Multi Purpose Vehicles: => Mk3 Volkswagen Sharan / SEAT Alhambra Owners Forum => Topic started by: woollymammoth on June 26, 2021, 11:16:43 PM

Title: \intermittent earthing problem between battery -ve terminal and engine metalwork
Post by: woollymammoth on June 26, 2021, 11:16:43 PM
I have had some recent issues with my Sharan 55 reg 1.9dti , where when the engine is stopped, mileage reading and clock resets to zero, and there seems to be a power loss preventing the ignition key starting the engine again. This condition normally resets itself after a few minutes, but can take longer.
I do not have a detailed wiring schematic, and so far not been able to download one due to no printed service manual.  While checking voltages I have seen instances of 12 Volts + being measured between the engine metalwork, and the -ve battery terminal. Arthritis makes tracing out the wiring difficult for me, so I wondered if anybody knows if there is an accurate schematic showing the layout of the earthing cables and straps. (I have noticed on the Ford galaxy manuals the earth points are labelled by E1, 2, 3 etc.) I would think the large brown 25mm2 cable on the battery -ve terminal, would eventually connect to the engine/gearbox for the starter motor return current.

Any advice would be most welcome. Regards John Crookes. 
Title: Re: \intermittent earthing problem between battery -ve terminal and engine metalwork
Post by: johnnyroper on June 27, 2021, 08:24:21 AM
Can't recall locations of the earth connections for engine (think it might be on the gearbox casing) however I would probably just add one direct from battery to the block somewhere even if it's just a temp measure to see if fault is resolved.
Have you checked the fuse box on battery for signs of overheating as that is also a common failure point causing power supply issues?
Title: Re: \intermittent earthing problem between battery -ve terminal and engine metalwork
Post by: Chrispb on June 27, 2021, 09:35:03 AM
Quote from: woollymammoth on June 26, 2021, 11:16:43 PM
I have had some recent issues with my Sharan 55 reg 1.9dti , where when the engine is stopped, mileage reading and clock resets to zero, and there seems to be a power loss preventing the ignition key starting the engine again. This condition normally resets itself after a few minutes, but can take longer.
I do not have a detailed wiring schematic, and so far not been able to download one due to no printed service manual.  While checking voltages I have seen instances of 12 Volts + being measured between the engine metalwork, and the -ve battery terminal. Arthritis makes tracing out the wiring difficult for me, so I wondered if anybody knows if there is an accurate schematic showing the layout of the earthing cables and straps. (I have noticed on the Ford galaxy manuals the earth points are labelled by E1, 2, 3 etc.) I would think the large brown 25mm2 cable on the battery -ve terminal, would eventually connect to the engine/gearbox for the starter motor return current.

Any advice would be most welcome. Regards John Crookes. 
Resetting trip counter can be fuse 32 blown. May be worth checking splice joint 32, look in knowledge base for more info.
Title: Re: \intermittent earthing problem between battery -ve terminal and engine metalwork
Post by: woollymammoth on June 27, 2021, 11:11:47 AM
Thank you for the prompt replies, I was looking on Ebay last night and found battery wiring looms for the Sharan for sale, and looking at the length of them it would appear the main earthing connection to the bodywork is under the battery mounting tray, so I will start there tomorrow and hopefully get to the bottom of this. JC