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Ammeter deflection on horn

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Ammeter deflection on horn

Posted by george_phillips at May 11. 2018

If I'm reading the wiring diagram correctly (55 ES2) the horn circuit goes up to, but does not pass through, the ammeter. Mine deflects to negative when the horn button is pushed. What's the routine for sussing this out? Electrics is not my favourite game!

George

Re: Ammeter deflection on horn

Posted by colin_peterson at May 11. 2018

Sounds right to me! Although on a later machine I'd expect the horn to be powered via the ignition switch. I don't remember if you could beep the horn on older bikes I've had, without first turning on the ignition. But the ammeter going to negative is what'll happen when you turn on anything – how far it goes would depend on if the engine's running and producing electricity, at what rpm, and what else electrical is on at the time. If there's enough electricity being produced, the ammeter might not show negative at all, but just dip a bit in that direction. HTH

Re: Ammeter deflection on horn

Posted by ian_soady at May 11. 2018

Normally both the horn and the brake light are fed from the battery side rather than the generator side. I believe this is so you don't get annoying deflections of the needle when they're used as the ammeter is really used to show you the "steady state" situation.

Re: Ammeter deflection on horn

Posted by colin_peterson at May 11. 2018

Previously ian_soady wrote:

Normally both the horn and the brake light are fed from the battery side rather than the generator side. I believe this is so you don't get annoying deflections of the needle when they're used as the ammeter is really used to show you the "steady state" situation.

True! I'd forgotten.

Re: Ammeter deflection on horn

Posted by george_phillips at May 12. 2018

Having slept on it I now realise that the ammeter never twitched n the "old days" when the horn was operated. I believe a PO has wired the horn circuit through the ammeter instead of wiring up to and from one side. I agree with Ian. The needle should not deflect when the horn is operated. More poking around inside the headlight shell!

Re: Ammeter deflection on horn

Posted by alan_osborn at May 16. 2018

The horn and stop light are both intermittent, hence which side you connect them to with regard the ammeter is not crucial. Some of the older horns where higher current hence not through the ammeter is prefered. But anomaly number one, some times if you press the horn button and it is connected direct to the battery the current goes through the horn and NOT the ammeter but the ammeter might show a small charge??? This is because the lower voltage thrown at the battery by the horn press causes the dynamo/regulator to crank up a bit, replenish the battery and raise its voltage hence increase its charge current marginally. The same can happen with the stop light, so seeing your ammeter increase its charge when you press the stop switch can be considered a good check.

Re: Ammeter deflection on horn

Posted by george_phillips at May 22. 2018

Thanks Alan. I'll check that out.

G

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