Why do my lights go out

[Trevethan]

OK quick question... When I run my engine all my lights go out. As soon as the engine goes off on come the lights...

Have I connected the wrong cable to the distribution panel or have I got a shot alternator?

Regards,

Nick

 

[Plum]

don't know the answer to your question, but I recommend you first see if your alternator is working OK. Put a digital voltmeter (see recent posting on this forum about "Maplin") across the battery after the engine has been stopped for at least an hour. The voltage should read between 12.2 and 12.7 volts. Now start the engine and within a few minutes the voltmeter should read between 13.8 and 14.2 volts. If it does, then the alternator is working.

Now, what exactly do you mean when you say "all my lights go out" which lights are you refering to? Is it only the lights that go out, or do other electrical devices stop working when the engine is running?

 

[aztec]

i have had a similar prob on an orion, ended up being the altanator, for some reason it started "taking" power from the battery, the faster the engine speed the more power it took, kinda reverse polarity.

so if you havn't changed anything, ie, the wiring, i'd go for the altanator.

 

[Trevethan]

The only 12 volt equipment connect via the panel is the lighting.. and when the engine runs the lights go out.. as soon as the engine sttops on they come. The wiring has been messed with, by me, as previous owner had by-passed panel for nav light, and only other electronics on board was VHF. so am trying to restore the panel and make the wiring safe again. Using my meter found +ve and -ve cables under the dash.

They are good sized cables so rightly or wrongly I assumed that there was only one of each and taped up all the others for another day.

I wonder if I have perhaps connected to teh wrong -ve.

The panel has an ammeter (I think) in it, not working like everything else - perhaps I have connected to the cable for that by mistake and when alternator run, 12 volts comes up the wrong way knocking out the lights?

Regards,

Nick

 

[halcyon]

When you say the lights come on with the engine off, do they come on bright, or a bit dim ?.
Sounds a bit like your earthing the lights through the engine equipment, alternator/starter.
You may have to get a multimeter, and check service battery earth to alternator neg terminal, and work around all the earth points. May help to attatch 15/20 foot of wire to earth probe on meter, allows you to wander around boat while maintaing a standard piont of reference.
You are looking for a voltage when you should not have one.


Brian

 

[VicS]

Please post the reason for this when you've solved it.

Vic

 

[pete]

I am not an electrician but if you have connected the neutral from your boat lights to the field wire ( charging light circuit ) when your engine is off you may get an earth through the alternator when you start the engine this becomes a live and you get no lights just the same as with your charging light good luck

Pete

 

[Trevethan]

When the lights come on they are bright.

I'll try and follow the alternator cabling and see where it goes.

Any ideas on what I should expect to see are welcome!

Engine is a Lister RH4W, and I think its a Lucas alternator but couldn't say which.

regards,

Nick

 

[andyball]

may well be an earth problem,as others have said- eg: earth for lights connected to the wrong place ...or maybe to the right place, but that place not connected to battery earth ( eg, with a hand-start engine the earths may be connected to the engine as an earth...but if there's no connection from engine to battery -ve terminal: you could get the symptoms described.

 

[Trevethan]

Its an electric start engine. But will check out cables to starter (recently renewed). As I recall there are 3 on the starter motor. A pair of really heavy ones and a lighter one.. I guess that one energises the solenoid from the ignition key?

Despite the high cost of living, it still remains popular.

 

[andyball]

if the starter has it's own earth(3 wires...), then what I said about hand-started ones could still apply, since the starter isn't necessarily electrically connected to engine block (paint/grease etc).

 

[stubate]

hang on a bit we are all jumping about with half arsed guesses,start from basics.
battery
ammeter
charge

check the ammeter, disconnect, put ohm meter across terminals, is it connecting thru? if it is it is working, the reason it wont show a charge or discharge is because it is wired in wrongly.

very simply think about a circuit, battery to earth on one side, battery to ammeter on other side, other side of ammeter to charge, if charging, current flows one way and makes ammeter move that way, if discharge the current flows the other way and makes ammeter flow the other way, if charge is balancing the ammeter shows neutral.
all the load to the boat should go thru the ammeter so make sure that it is rated for the load you are putting to boat, by the way the starter circuit does not go thru the ammeter !! for obvious reasons.
if you have now got your head around the simple circuit, use that to figure out how your boat circuit is working, dont forget it will not be wired as simply as the above.
if you need any more help email me stu@llangollen.co.uk

 

[Trevethan]

Problwm solved. Unsure how. Well I know how I solved it..

Previous owner has realled buggered areounf the electrics... all unlabelled, and large numbers of redunant cables.. Figured I should start from scratch.

I disconnected every lead running to the panel except the two that carry current to the ignition switch and the panel. none were labelled), then multimetre in hand tried each cable in turn. (About 15 of them)

Found 2 that showed 13+ volts travelling hte right way I am assuming the rest are senders and will trace later.

Traced cables and labelled. Still not getting much (if any) output from the alternator, but that didn;t begave before either so a trip to Lucas is called for to get it looked at


regards

Nick

Despite the high cost of living, it still remains popular.

 

[VicS]

Thanks for coming back and reporting your findings.

One thought about lack of output from the alternator: Initially the field energising current comes via the "ignition switch" and the waning light so if you have disconnected the wiring to the light (or if the bulb has failed) the alternator won't start to generate.

As you sort things out and reconnect it all I suggest you draw yourself a wiring diagram.