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Old 17-01-2014, 22:42   #1
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ignition switch - no 12v

I'm trying to help a friend with his boat out of the water doing a job which required the engine to be disconnected and shifted forward temporarily. The engine, a two cylinder Ford, has now been replaced but we can find no 12v at the ignition switch. The switch has JC printed on it and has 6 terminals (G1 and G2 joined, B1 and B2 joined, S, and M) None of these have any power! The battery has connections to the domestic fuse board but no obvious connection to the ignition switch. In fact the battery's only other +ve connection is the heavy cable direct to the starter motor. Where on earth does the ignition switch get its power from? It was running fine and no work has been done in the electrical circuits apart from disconnecting the engine wires prior to moving the engine. I am completely at a loss for ideas and would welcome suggestions. I have checked that a hot wire from the battery to the starter solenoid works fine and the engine turns over. There must be some obvious solution which would enable us both to sleep again!
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Old 18-01-2014, 00:10   #2
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Re: ignition switch - no 12v

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Originally Posted by kiwikol View Post
I'm trying to help a friend with his boat out of the water doing a job which required the engine to be disconnected and shifted forward temporarily. The engine, a two cylinder Ford, has now been replaced but we can find no 12v at the ignition switch. The switch has JC printed on it and has 6 terminals (G1 and G2 joined, B1 and B2 joined, S, and M) None of these have any power! The battery has connections to the domestic fuse board but no obvious connection to the ignition switch. In fact the battery's only other +ve connection is the heavy cable direct to the starter motor. Where on earth does the ignition switch get its power from? It was running fine and no work has been done in the electrical circuits apart from disconnecting the engine wires prior to moving the engine. I am completely at a loss for ideas and would welcome suggestions. I have checked that a hot wire from the battery to the starter solenoid works fine and the engine turns over. There must be some obvious solution which would enable us both to sleep again!
On my Yanmar the switch gets its power I believe from the starter motor at the post where the battery is connected.
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Old 18-01-2014, 01:01   #3
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Re: ignition switch - no 12v

G 1 and g2 could be ground. b1and b2 could be positive to bat. S could go to starter solenoid positive m to fuel pump gauges and kill solenoid if equipped. Battery positive to panel usually comes off the starter positive. Check the functions with a volt meter. To be safe.
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Old 18-01-2014, 01:34   #4
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Re: ignition switch - no 12v

Much appreciate your replies. The solenoid/starter has a main (big) cable direct from the battery but no other connections to this termainal. On the ignition switch, the G terminals connect to the glow plugs, the B terminals connect to the starter motor terminal on the solenoid which has the strap to the starter brush, the S terminal connects to the solenoid tab, and the M terminal connects via a fuse to the battery indicator meter/oil pressure alarm, and temp alarm. none of these have any voltage showing on my multimeter so I really can't figure out where it gets it's power from.There are no obvious wires missing or broken, and as I said, it was working fine before we disconnected everything from the engine! It has me beat. No work was done in the area of the ignition switch so I really don't think anything has changed here. It just doesn't seem possible for the switch to have any provision for a +ve supply - really weird.
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Old 18-01-2014, 08:42   #5
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Re: ignition switch - no 12v

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Originally Posted by kiwikol View Post
Much appreciate your replies. The solenoid/starter has a main (big) cable direct from the battery but no other connections to this termainal. On the ignition switch, the G terminals connect to the glow plugs, the B terminals connect to the starter motor terminal on the solenoid which has the strap to the starter brush, the S terminal connects to the solenoid tab, and the M terminal connects via a fuse to the battery indicator meter/oil pressure alarm, and temp alarm. none of these have any voltage showing on my multimeter so I really can't figure out where it gets it's power from.There are no obvious wires missing or broken, and as I said, it was working fine before we disconnected everything from the engine! It has me beat. No work was done in the area of the ignition switch so I really don't think anything has changed here. It just doesn't seem possible for the switch to have any provision for a +ve supply - really weird.
I don't believe that the B terminal wire should go to the big terminal on the starter that has a strap to the starter brush, it should go to the other big terminal. So large battery cable brings +12 to starter, small wire that goes to B on switch is on the same terminal, to provide the +12 for the switch. Start position of switch connects B to S. S goes to small terminal on starter. This causes the plunger to engage the pinion to the flywheel. When the solenoid (plunger) reaches its full travel the contact on the back of it connects the two big terminals (internally) together applying power to the motor that turns the flywheel.

The strap terminal gets power from the large battery terminal after the solenoid engages. As far as I know nothing is connected to the strap terminal externally (other than the strap).

You could check most of this with a DVM before applying power to anything.
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Old 18-01-2014, 12:46   #6
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Re: ignition switch - no 12v

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I don't believe that the B terminal wire should go to the big terminal on the starter that has a strap to the starter brush, it should go to the other big terminal. So large battery cable brings +12 to starter, small wire that goes to B on switch is on the same terminal, to provide the +12 for the switch. Start position of switch connects B to S. S goes to small terminal on starter. This causes the plunger to engage the pinion to the flywheel. When the solenoid (plunger) reaches its full travel the contact on the back of it connects the two big terminals (internally) together applying power to the motor that turns the flywheel.

The strap terminal gets power from the large battery terminal after the solenoid engages. As far as I know nothing is connected to the strap terminal externally (other than the strap).

You could check most of this with a DVM before applying power to anything.

Ahhhh!!! Wow, I think you may have nutted it! Have yet to try it but that's the most likely scenario. Having the big solenoid/starter wire and the other wires currently on the remaining solenoid terminal (incorrectly?), actually on the same terminal will give me 12v at the ignition switch - and the bare terminal only livens up when the solenoid is activated. Yes! All seems logical now exactly as you say! Well done - watch this space!
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Old 18-01-2014, 14:09   #7
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Re: ignition switch - no 12v

A 'positive' result!! many thanks John - there's a cold beer waiting for you in NZ
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Old 18-01-2014, 14:41   #8
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Re: ignition switch - no 12v

Pretty sure Cal40john is correct. I've only ever seen one thing connect to the strap side of the solenoind and that was a kill solenoind that required a big pull circuit upon startup and then a smaller hold circuit.
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