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Lazy alternator light!
prawnabie - 19/12/08 at 10:43 PM

Hi

I rewired the locost I am restoring about 3 weeks ago. Everything was fine until today! The alternator light refused to go off on my acewell when the engine was running and the voltage was showing 11.7 when the engine was running. It has been fine up until now!

I first though the alternator had packed up - luckily i have a new alternator for my crossflow to swop it with - still had the same problem - light stays on even when revving it.

I have used the beeper on my multimeter to check the wiring and it is all sound with no breaks. I desperation I hooked up a wire from the live on the battery to the light output on the alternator - with a bulb in the middle. When I started it the bulb was still lit, but went off when I revved it and so did the light on my acewell. It stayed off even when idling.

It has baffled me as it has been working fine for the last few weeks and not had started doing this - any ideas?

Thanks

Shaun

omega 24 v6 - 19/12/08 at 11:10 PM

The original wire from the bulb to the alt COULD be chaffed to earth causing the light to stay on. Check it with a meter but you'll need to disconnect at the alt first.

Dusty - 20/12/08 at 01:44 AM

I suspect the alternator is not getting a big enough excitatory current through the acewell light so was not charging. Your bypass with the bulb fixed this. Quite why it should do it now I don't know. I assume the Acewell is not new? Maybe your rewire has taken out the alternators secret ignition live supply and there was a scrap of residual magnetism in the alternator which was allowing a charge but which has only just faded.

prawnabie - 20/12/08 at 01:45 AM

Just checked and there is no circuit to earth from the charging lamp wire with the plug disconnected from the alternator.

Really weird as it works with a substitute warning light, athough i do have to touch the gas pedal for it to start charging.

Thanks

Shaun

David Jenkins - 20/12/08 at 08:44 AM

quote:
Originally posted by prawnabie
Just checked and there is no circuit to earth from the charging lamp wire with the plug disconnected from the alternator.

Really weird as it works with a substitute warning light, athough i do have to touch the gas pedal for it to start charging.


I can't suggest anything for your main problem that's different from what's been said already. However, I also get the 'having to touch the gas pedal' thing - in my case, I have the steel replacement crank pulley from Burtons which is a fair bit smaller than the original pressed steel one. This spins the alternator a bit slower than before, so it needs a little blip to get going.

I don't know if you also have one of those pulleys...

omega 24 v6 - 20/12/08 at 10:23 AM

Ah I should have re read the original post. If your warning light is part of the acewell then you need to check it as the earlier poster said. IIRC you need a 3 watt bulb to excite a lucas alternator. So probably most of the others will be similar. On my build I have an led warning light but hidden behind the dash I have a bulb in parrallel circuit with it in order to make it work.

prawnabie - 20/12/08 at 11:10 AM

Ahh thanks guys - I do have an "alloy" pulley fromn burtons and the acewell is new.

Just a bit wierd that it used to work fine before - although the car is still being built so I guess it was just a glitch lol.

Thanks for you help, I will wire in a bulb and hide it under the dash!

Shaun