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Author Topic:   Wiring Blue wire for dash and switch lights
4whaler posted 05-21-2009 06:28 PM ET (US)   Profile for 4whaler   Send Email to 4whaler  
Were does the blue wire for the instrument dash gauges and the switch panel get terminated? There are three wires going into the switch panel a red, black and blue, the first two are easy to figure out but does the blue wire which powers the lights a hot in or negative out? I think its the hot in with the black wire being the common ground for all? And where does the black go on the one DPDT ON-OFF_ON switch I have on the panel for the bow and anchor lights. I have the hot positive coming in to 2 and 5 the middle tabs and the anchor coming out of 6 with a jumper from 1 and 3. The blue goes on tab 7 for the lights but that leave me wondering where the black goes since all the switches are jumpered together for the black and blue while the red is run thru a separate fuze block of different amps for each switch.
jimh posted 05-21-2009 09:28 PM ET (US)     Profile for jimh  Send Email to jimh     
In every electrical distribution I know of, the switch is always in the positive lead, and particularly so in boats where to do otherwise is to invite galvanic corrosion. It is cumbrous to describe electrical circuits in a narrative. Draw a schematic diagram and show it to us. That said, here goes:

Wires connect elements in the circuit. The wire which provides current for illumination of the gauges themselves is typically provided with blue insulation.

The blue wire for the gauge circuit is typically wired so all gauge illumination circuits (or the loads) are in parallel, and current to them is supplied from a switch which controls the gauge illumination function and is wired to a source of 12-volts.

On switches which themselves are illuminated there typically must be a connection to the negative side of the circuit for the switch illumination circuit.

swist posted 05-22-2009 04:12 AM ET (US)     Profile for swist  Send Email to swist     
I would only add that in some cases there is no separate switch for the gauge illumination circuits and the blue wires are simply tied to the ignition circuit (purple wire), hence the gauges are lit whenever the key is in the "on" position.
pglein posted 06-01-2009 03:24 PM ET (US)     Profile for pglein  Send Email to pglein     
My gauge lights are wired to the navigation light circuit. When the navigation lights come on, so do the instrument lights. This makes sense to me, as there is no need to iluminate the gauges during the day, and doing so would only cause the bulbs to burn out prematurely.
4whaler posted 06-08-2009 05:00 PM ET (US)     Profile for 4whaler  Send Email to 4whaler     
I have two conditions.

One is the instrument gauges lights blue wire Im going to wire to the dedicated lights hot/positive bus that is powered from the switch panel nav/anchor light ON position wire and will illuminate only when I turn on the running bow lights (I have compass light here too, but the do not come on when the anchor only ON is switched.

Two: The actual switch panel LED lights that shows if the switches in the panel are ON or OFF needs to be illuminated at all times so I'm going to take that blue wire to the ignition purple. One of these switches is the above mentioned nav/anchor three way (nav/anchor ON-OFF-anchor only ON).

Hard to put in words this...

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