Ignition Light

[Nightwatch]

Hello All.

We have an issue with the ignition light on Nightwatch, during the day!

Engine runs okay, for hours. Switch of and engine stops as you would expect. Take the key out and hang it up.

However,the ignition light comes back on and stays on. First time this has happened. Barrus Shire and control panel. I have fiddled with wires in 'engine ole, stays on. Isolated the engine battery circuit, it stays on. 

A bit worrying. Any ideas. Is it perhaps a dodgy ignition switch? Or whatever. Help always welcome here.

Martyn

 

Edited October 1, 2017 by Nightwatch

[WotEver]

How do you monitor your Batteries? Is the charging voltage and current normal when the engine is running?

[Tony Brooks]

Also see Sir N's recent post on a very similar topic elsewhere on here - he diagnosed a shorted out main positive diode in the alternator.

A shorted diode would put 12V onto the D+ (warning lamp terminal). That can back feed through the warning lamp with the ignition off and try to power the other warning lamps and instrument's - hence it being on but possibly at a  reduced brightness.

It would also give a lower charging voltage and current, hence Wotever's question.

 

Edited October 1, 2017 by Tony Brooks

[Nightwatch]

Sorry I haven't been back sooner. I fiddled some more,took off the control panel and fiddled in there. It went off. Just done an oil and filter change since. Engine now running. According to my Victron 702 gadget it is charging at 15 volts. 14.8 amps with just 1.6 amp hrs on the reading. I will carry on charging til the charging amps drop into lower single figures. New batteries 440 ah.

I believe a good fiddle fixes the problem in 90% of issues. 

[Tony Brooks]

Sounds like you may have an intermittent short circuit to metal on the warning lamp to alternator wire.

[Nightwatch]

Thanks Tony. I will investigate tomorrow. It did it again after charging the batteries half an hour ago. I was fiddlin' and it just went off when I paused my fiddle.

[Tony Brooks]

Please ignore my last post. As I wrote it I realised it was rubbish and deleted it, now it wont let me edit it.

After that I posted (seems to have gone) asking how many piggyback connectors you have on the back of the ignition switch because if the lights on with the ignition off it must be getting a feed from somewhere. Messing about behind the panel should not solve a shorted diode problem and a short on the wire between lamp and alternator would not put the lamp on with the ignition off. Conclusions:

1. A live feed shorting to the switch side of the warning light circuit.

2. Faulty ignition switch but I don't feel that is likely.

Its a mystery!

[Nightwatch]

I shall run the engine again later and see what happens. As mentioned earlier, I took off the control panel and disconnected each wire and pushed back on. It didn't solve the issue. 

Forgive me, but electrics really confuse me. When diodes and voltages get mentioned my eyes cloud over as I've no idea what can be done and how to do it. But, having said that I am willing to learn. I have gathered masses amounts of knowledge over the fifteen years of being a boat owner. Electrics still baffle.

Thanks for all the suggestions so far.

[Sir Nibble]

How many alternators do you have and which one indicates the problem?

[Tony Brooks]

Don't worry about diodes apart from accepting that in this case they are inside the alternator and when they fail its a bad thing. Leave the testing of the diodes themselves to others. However you really need to feel confident enough to decide if the alternator is faulty or not.

The B+ terminal on the alternator is the biggest one with a thick wire on it that is the main charging positive, often but nor always coloured brown.

The D+ is a smaller terminal, often a 6mm blade but sometimes a smaller stud connection that is connected to the warning lmap. You may have another thin one that feeds a revcounter or just possibly a split charge relay. The way to identify D+ is there are no marks is to turn the ignition on and take eacah thin cable off in turn. The one that puts the warning lamp out is D+.

Having identified the terminals set a meter to 20 volts DC. The voltage scale will be shown by a V and the V DC will be identified by two parallele lines with one line as small dashes.

Connect the meter to those two terminals, start the engine and rev it. Report back what volatge it reads. I hope it will be well under 1 volt.

I doubt this will work with a needle type meter.

This together with the charging volatge (just connect the meter across a battery and the current (amps - not sure how you can measure thay unless you have a clamp type DC meter) shoudl allow some of us to tell you if the alternator is faulty. I would rather the readings were taken towards the end of a charging period though.

 

Edited October 2, 2017 by Tony Brooks

[Nightwatch]

Brilliant Tony. 

Thats what my limited brain needed.

We have to move today, weather permitting, and I will do as suggested once we get to where we're going.