Erratic compass

[cagey]

Real help please
Replaced Plastimo 135 Olympic Compass with newer model (same type)
nothing around binnacle, (installation), has changed but compass is unreliable. Have excluded extranious influences (engine, instruments etc.) nothing interferring with compass( cans, keys, mobiles), but at times and never in the same place the card swings erratically. What is going on.
Thanks
Keith

 

[damo]

Belt buckle? Loose screw or tool left inside binnacle mount? Sailing over shallow wrecks?

 

[sarabande]

Any intermittent electrical instruments or systems being switched on or off ?

 

[Porthandbuoy]

Speaking from my own experiences:-

5 year old son with a bumbag full of magnets.

Copper coins which aren't.

Brass plated steel screws sold to me as brass.

 

[Ruffles]

Sounds faulty to me.

Even if the new compass hasn't been 'swung', given that the previous one worked ok and the new one is in the same place, it should at least be consistent.

 

[oldsaltoz]

Just a thought, but have you checked the compass illumination circuit to make sure the switch in in fact still on the positive (+) side of the wiring, if connected to the negative (-) side you would have a current in the cable, also note this cable must be twisted to eliminate an electromagnetic field.

Avagoodweekend......

 

[VicS]

[ QUOTE ]
make sure the switch in in fact still on the positive (+) side of the wiring, if connected to the negative (-)

[/ QUOTE ] Sorry???

Magnetic fields around wires are caused by a current flowing in the wire. It matters not a jot whether the switch is in the positive or the negative. If it is open no current will flow, the bulb will not light and no magnetic field will exist.

It is correct though that the wires should be twisted together so that the fields produced by the individual conductors cancel each other out when the light is switched on.