Cig Socket making "on" lights, light up - just need a pointer

[dominic221]

Hi There
I'm looking for a pointer in the right direction, as I'm sure this needs to be looked at to be fixed. Boat has been out of water since December. No modifications that would interfere with electrics has been done. I have issue now that when I plug anything into the cigarette socket at the helm, my switch "on" lights light up. If I turn the switch off the light goes off. I'm sure I've got a loose wire or short somewhere, just looking for a pointer as to which of the rainbow spaghetti bowl of wires I should take a dig at first.

I know its a bit vague, I can do any all tests or give more info if asked. Anyone fancy a challenge

Dominic

 

[sarabande]

are you talking about a cigarette socket which has a dedicated ON switch, or an ON switch for something else ?

Are you plugging in a device which has a battery of its own ?

 

[dominic221]

Let me try and explain a bit better.

setup
Cig socket, no on/off switch.
Panel Switches = wiper, bilge, horn, nav lights. etc. All panel swiches illuminate when switched on. Normal state = Off


When I plug, say a 12v vacum in, which worked fine all last year in the same socket, and power it on, all the panel lights illuminate. If I switch a panel switch to on, the illination goes out. When I switch vacum off the panel switches return to expected illuminated state.

I have tried replacing cig socket, no difference.

 

[sarabande]

sounds as if the cig socket power switch is providing juice to all the other switches - which might mean that the cig socket is a) near its current limit of about 12amps b) the socket leads have got switched over somehow, but I'd expect a fuse or MCB to go pop at that point.

Does anything look or smell unusual when you open the panel ?

 

[dominic221]

no nothing smelling. no trips or fuses blowing.
All negatives goto a bus bar, only switching on positive.

So I'm thinking that the socket is somehow shorting the negative to the panel light bulbs. just havent the foggyist of where to start. except maybe just plug the cig socket up with some silicone and put a do not use sticker on it.

 

[sarabande]

well it's not the socket itself at fault. Before you declare it out of bounds, perhaps try taking the + and - leads of and insulating them. Do the switch lights come on ? If you join them together, and repeat the test on the switch ligts, that would mean the + is acting as - for them.

What's mysterious is the change over winter. A dead mouse across a terminal ?

 

[PaulGooch]

Carefully check the negatives for the cig socket and the switch illumination.

 

[HotProperty]

Sounds like a bad earth at the busbar check for tightness and cleanliness of the wires to and from it, you may even find the light earth shares the same earth point as the cig socket as if the connection is poor the component will try and find a new earth path, in this case your lights. If your not sure which earth it is once the hoover has been used the offending connection will be hot. Good Luck

 

[BGW]

Hi There
I'm looking for a pointer in the right direction, as I'm sure this needs to be looked at to be fixed. Boat has been out of water since December. No modifications that would interfere with electrics has been done. I have issue now that when I plug anything into the cigarette socket at the helm, my switch "on" lights light up. If I turn the switch off the light goes off. I'm sure I've got a loose wire or short somewhere, just looking for a pointer as to which of the rainbow spaghetti bowl of wires I should take a dig at first.

I know its a bit vague, I can do any all tests or give more info if asked. Anyone fancy a challenge

Dominic

If nothing has changed since it was working before I would suspect a bad earth. - A similar thing can occasionally be noted on cars - A bad earth can cause the lights to behave in a very odd fashion - for example when the brake is applied, the lights come on dim with some or all of the other lights at the same time.
For a temporary test, wire the socket directly to the +ve and -ve of a battery.

 

[oldgit]

"Carefully check the negatives for the cig socket and the switch illumination."

This would be my very first port of call as well.Even just removing a lucar connector and refitting it will clean connection.Plug in whatever causes the problem and have a good feel round will sometimes produce a warm joint which indicates high resistance ie. bit of corrosion perhaps due to this rather damp winter.
Maybe even the connector will "feel" a bit rough and look a bit less shiney or darker than other connectors.
Always worth spending 10 mins groping and fiddling around BEFORE dismantling half your dash and electrics.
In addition take along long bit of decent wire and directly connect cigar lighter earth to battery earth,if solves problem it will be a simple fix.

 

[VicS]

I've had a little think about this since last night.

As has been suggested it is almost certainly a bad negative connection to or within the panel.

Good enough for the small current that the switch illumination bulbs require to work normally by not good enough for the vacuum cleaner.

When plugged in the current flow is from positive through the vac to the negative busbar to which all the bulbs are connected. Then since the negative connection to the panel is dodgy the flow is ( backwards) through the bulbs then through each of the items mentioned, horn, wiper, bilge blower, nav lights etc, ultimately to a good negative connection(s).

Therefore check the negative supply to the panel and within the panel to the common negative.

Just checking with a multimeter wont find the trouble cos it does not take enough current.
You may be able to trace the problem with the vac plugged in and all the bubs glowing.

 

[Colvic Watson]

Could the recent very cold weather have been cold enough to crack a bad solder? I wondered if this has caused a wire to slip and be just touching another terminal. Can -15C do that?