Just had my alternator tested as I thought I was playing up. Turns out the alternator is fine, charges right and puts out the correct amps.

Anyway, put it back on the car and realised that the switched live that goes to it was actually a feed to some thing else. So, I ran a new switched live to it and now when I turn off the engine it continues to run. The only way to switch off is pull the coil plug to cut spark.

What on earth is going on? I thought the alternator just needed a +12v switched to energise it, but for some reason it keeps the engine running.

Can anyone suggest anything that might cause this. I checked the 12v and it goes off when ignition turned off.



Thanks
Andy

Hi,

Had the same problem with mine.

I put a resistor in the live feed to the bulb in the dash and now works fine.

quote:

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Originally posted by Acc8braman
Hi,

Had the same problem with mine.

I put a resistor in the live feed to the bulb in the dash and now works fine.

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Hi,

Sorry, it wasn't a resistor, it was a diode.

Something like this


[img]https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcR2vltnFSBhNMF6XyAQwONZbnfgzhowmiwH0i_JOtrgFIPizIX3vg[/img]

Not sure which alternator you are running but, normally you would have 1 large wire running direct to the battery (possibly with a high amperage fuse) and one wire that goes from a switched live through a convention bulb and to the warning light terminal on the alternator. This warning lamp wire provides the excitation for the field windings. The bulb needs to be able to pass enough current for things to work, so a LED will not work.


This is assuming it's not an ECU controlled smart charge alternator.

I have a 1N4004 diode and a 150 ohm 5 watt resistor in the circuit around the charge light.

Charging Circuit
Maybe when installing the new switched live wire, it bypassed these components (if fitted).