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Doesn't Turn Off


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#1 bluemini1979

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Posted 23 November 2019 - 04:43 PM

Good evening.

With my car engine running, when turning the ignition switch to the off position the engine stays running and the charge light illuminates in the clocks. When the alternator is unplugged it stops the engine. Have I wired something wrong or do I need to add something in line somewhere.
Thanks

#2 Homersimpson

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Posted 23 November 2019 - 05:12 PM

It sounds to me like you have wired the ignition incorrectly so that the coil always has power, when the car isn't running with the keys out of the ignition measure the coil voltage and see if its always live.

 

The reason the ignition light comes on is that it works by being connected between the alternator and the switched ignition circuit, when the ignition is on the 12V supply from the igntion goes to the igntion warning light then to the alternator (which isnt turning so producing no power and acts like an earth).  The light is therefore on.

 

When you start the car the alternator outputs 12V (I know its more but for simplicity lets say 12V) and therefore the voltage on both sides of the ignition warning light is the same and it goes off.

 

In your case it seems that when the igntion is off the alternator is still turning and producing 12V as the engine is still runing and this time the ignition circuit is at 0V because your are effctivly getting an earth through anything thats also connected to the ignition circuit (a similar principle to how the single indicator warning light works by being wired between the left and right hand indicators).

 

I would treat the ignition warning light as an indicator that the ignition switch is working correctly and it seems that you just have the coil wired up wrong, presumably to a permanent live.  This does need to be resolved as it won't do the coil any good to be on all the time.



#3 bluemini1979

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Posted 23 November 2019 - 05:26 PM

Thanks, it's running specialist components efi. Power is being taken from ignition live fuse and permanent live fuse from the standard fuse box. Fuse box goes to 0v when the switch is off.

#4 KTS

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Posted 23 November 2019 - 08:46 PM

seem to recall a post recently with the same issue - in that case the problem was the alternator output to the ignition lamp was enough to cause the ecu to think the ignition switch was still providing power.

Solution was to put a diode in the line between the ignition switch and the ignition lamp

Edit : found the post I was thinking of.

http://www.theminifo...city/?p=3617895

Edited by KTS, 23 November 2019 - 08:52 PM.


#5 Homersimpson

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Posted 24 November 2019 - 08:46 AM

seem to recall a post recently with the same issue - in that case the problem was the alternator output to the ignition lamp was enough to cause the ecu to think the ignition switch was still providing power.

Solution was to put a diode in the line between the ignition switch and the ignition lamp

Edit : found the post I was thinking of.

http://www.theminifo...city/?p=3617895

 

If thats the case its easy to prove, just remove the ignition warning light bulb and if the problem stops you have the answer.



#6 bluemini1979

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Posted 24 November 2019 - 01:30 PM

Diode in the wire to the light sorted it. Thanks all




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