Author Topic: B40 wiring diagram  (Read 171 times)

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Greenfield

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B40 wiring diagram
« on: 12 March, 2019, 17:48:59 »
I don't find the Haynes wiring diagram of much use for my 1961 B40. I'm particularly interested in the connections to the ignition switch. Can anyone point me in the right direction?

berniej

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Re: B40 wiring diagram
« Reply #1 on: 12 March, 2019, 18:33:38 »
Would highly recommend the Rupert Ratio book which includes alternative options like 12V conversions.

Cheers,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
Bantam D7
C15 project
B40 Sportsman project

AdrianS

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Re: B40 wiring diagram
« Reply #2 on: 13 March, 2019, 09:46:16 »
I have got a copy of the wiring diagram in the owners handbook. I think it is no better than what you have got.
It is difficult to fathom out how the switch wiring works - if anyone has a simple guide, I wouldn't mind having a copy too!

JulianS

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Re: B40 wiring diagram
« Reply #3 on: 13 March, 2019, 10:40:19 »
This is from the Lucas service manual. Not an easy loom, you need to trace the alternator output Green/Yellow cable via the ignition and lighting switch in  the different switch positions, until it gets back to the rectifier.

With the riginal 6 volt system, with no voltage regulator in circuit, the lighting switch is also a charging switch to crudely control the alternator output.

With ignition "on" the green/yellow a/c output enters ignition switch at terminal 17 and leaves at terminal 18 as black and goes to lighting switch terminal 5. With headlight "on" it emerges from terminal 7 as green/black to the rectifier giving full alternator output.

Following the wiring in different switch positions will show how the output is reduced by the internal connections.

A 6 volt system with a proper regulator and a 12 volt system dont need the coil switching to control output.

Greenfield

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Re: B40 wiring diagram
« Reply #4 on: 13 March, 2019, 16:01:29 »
Got it.
I should be able to now see the wood from the trees. Its always a bit of an issue when things have been messed about over the years, and wires no longer have the correct colours.
Many thanks, I knew that there'd be an answer out there somewhere.