Thanks Jim, that good to know. I assumed that from the symptoms but didny know. The alternator voltage was alternator B+ to earth on engine. Will start tomorrow with earth to body which should then tell me if problem is with earth or positive. Although will clean and check all.
On Sat, 14 Jul 2018, 17:46 Jim Hearne, <[email protected]> wrote: > 15V from the alternator where ?, on the warning light wire or the main > terminals as well. > If it's the main terminals as well but only 12v at the battery then it > must be a poor and broken connection between the alternator and starter. > Either the power wire or the earthing. > > Unless it's an injection engine then there is no diode between the warning > light connection on the alternator and the warning light. > So the warning light will come on with a voltage difference in either > direction. > On injection engines there is a diode so the bulb only lights if the > battery voltage is higher than the alternator voltage. > Which is what you are seeing. > > Jim > > On 13/07/2018 22:58, Nigel Plant wrote: > > Yes, I'm around there. Not had much time today, but did hook voltmeter up. > 15v from alternator, no difference across battery between engine running > and not, around 12.6V indicating a poor connection across starter. Main > battery earth and all auxiliaries cleaned with no difference. Am favouring > Steve's input and will clean/ check all leads between battery and > alternator on Sunday, they are very oily! > The bit I am struggling with is 15v from alternator going to ignition > bulb, why does it light up? Is it because alternator is supplying a higher > voltage to bulb than it receives from battery. So there is a nett 2.5 v > across the bulb. I had always assumed light glowed when battery voltage was > higher than alternator output. Guess it's all logical unless a diode is > present preventing a reverse current. > Some of this is rhetorical haven't really got my thoughts together yet. > Still will get there. > PS Am sorry that me posting this has caused other 2+2's to come out in > sympathy 😀😀 > > On Fri, 13 Jul 2018, 21:15 'Jamest142' via Quantum Owners Group, < > [email protected]> wrote: > >> Hi >> >> This is really strange - must be down to the weather... Q2-002 had the >> same problem, I thought it was the battery, changed it, then a new >> alternator. I eventually found thanks to Jim senior that there is a wire >> from the battery which goes from the battery negative to just above the >> starter motor - clamped by the bell housing for the clutch - nice thick >> wire, but totally covered in oil and crud. When I touched the engine end - >> it moved. I just tightened it up again, and the problem seems to have gone >> away. I have got a secondary battery earth going to the 'wrong' side of >> the clutch bell housing, but this does not seem to have much effect as it >> has at least 5 joins before it gets to the alternator. >> >> TTFN >> >> James T >> Q2-002 >> -- >> -- >> You received this message because you are subscribed to the Google Groups >> "Quantum Owners Group" group. >> To post to this group, send email to [email protected] >> To unsubscribe from this group, send email to >> [email protected] >> For more options, visit this group at >> http://groups.google.com/group/quantumowners?hl=en >> >> IMPORTANT NOTE: All information presented herewith is provided on an "As >> Is" basis, without warranty or the implication thereof. 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