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Ray White
Joined: 02 Dec 2014 Posts: 6330 Location: Derby
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Posted: Mon Dec 13, 2021 11:11 am Post subject: Ignition warning light. |
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How does it work?
I understand how power leaves the battery and passes through the ammeter and voltage regulator onto the ignition switch and from there to one side of the warning light. The other side of the light goes to the D terminal of the control box and earthed.
When the engine is not running (or only slowly) the dynamo will produce very little power so power from the battery will turn the light on.
When the engine runs faster power from the dynamo equalises that from the battery and cancels itself out ,,,so with no current flowing through it, the light goes out.
At this point I become confused. If current from the dynamo exceeds that from the battery going through the warning light, why does it not illuminate? |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4109 Location: South Cheshire
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Posted: Mon Dec 13, 2021 3:03 pm Post subject: |
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In normal running the battery and dynamo voltage are more or less equal, so there is little or zero potential difference across the ignition lamp.
Dave |
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Ray White
Joined: 02 Dec 2014 Posts: 6330 Location: Derby
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Posted: Mon Dec 13, 2021 4:40 pm Post subject: |
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ukdave2002 wrote: | In normal running the battery and dynamo voltage are more or less equal, so there is little or zero potential difference across the ignition lamp.
Dave |
Thank you Dave. I suppose the regulator somehow limits what goes to the battery so the light stays off? |
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peter scott
Joined: 18 Dec 2007 Posts: 7121 Location: Edinburgh
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Posted: Mon Dec 13, 2021 4:43 pm Post subject: |
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The ignition warning light receives power when the ignition switch is on and other side of the warning light is connected to the frame of the control box and the D terminal of the dynamo. With the dynamo stationary the frame connects to chassis ground through the shunt coil but when the dynamo gives sufficient output the frame rises to battery voltage so there is now no voltage across the warning light.
Peter _________________ http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon |
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Ray White
Joined: 02 Dec 2014 Posts: 6330 Location: Derby
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Posted: Mon Dec 13, 2021 4:49 pm Post subject: |
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Thank you Peter. I will go away and think about it. |
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alastairq
Joined: 14 Oct 2016 Posts: 1955 Location: East Yorkshire
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Posted: Mon Dec 13, 2021 5:26 pm Post subject: |
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Or, does the bulb simply shine backwards?? _________________ Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
----------------------------------------------
Ford Pop chassis, Ashley 1172 bodyshell, in pieces. |
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Ray White
Joined: 02 Dec 2014 Posts: 6330 Location: Derby
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Posted: Mon Dec 13, 2021 6:00 pm Post subject: |
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alastairq wrote: | Or, does the bulb simply shine backwards?? |
Don't be silly...you know it's all magic !! |
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