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3-Way Switch Wiring Question

Old 07-01-2012, 08:51 PM
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Default 3-Way Switch Wiring Question

I've always done all the wiring on my boats and never had a problem, but this one has me pulling my hair out. I know I'm missing something obvious.

I replaced my old bilge pump (two wires) with a new Rule 750 (3 wires). Decided to replace the old lighted on/off rocker switch on my panel with a lighted 3-way. Found a source that sells the old McGill rockers, so I have an exact match on the style/size. Bought a few of these switches: http://www.oempartsllc.com/switchroc...0852-0180.aspx The intent is to push the top of the toggle and have the pump in auto mode, center position is off, and bottom is manual. No problem so far, but now I can't figure out how to get the light to work in either mode without everything coming on.

Here's the inside of the switch, with the rocker in place:


Here's the inside with the rocker removed. I added the numbers as a reference point:


Laying on its side, here's the back, with the corresponding reference numbers:


Now comes the weird part. Although its hard to see in the first two pictures, the bulb is hardwired between number 4 and 5.

Tried a couple different combinations, but ended with this, and it still does not look right:
1 - Brown (auto) wire from pump
2 - 12v+ fused
3 - Brown w/white stripe (manual) from pump
4 - jumper to #1 (how else would the light work?)
5 - Black (ground)

Flip the rocker to Auto, the light comes on. I press the test button on the pump and it comes on for a couple seconds. So far, so good.

Flip the rocker to Manual, the light comes on and the pump starts. But what I'm worried about is that with the jumper from #5 to #1, the Auto circuit is also energized. So, there would be the possibility that if the float were to close that circuit while the pump is already running manually, it might send the planet Mars hurtling through space and wipe out planet Earth.

Now I'm thinking I may have ordered the wrong switch. This one is Single Pole Double Throw. Will this work for what I'm trying to do (auto/off/manual)? Or should I be using a Double Pole Double Throw?

This is REALLY giving me a headache!

Last edited by johnmsch; 07-01-2012 at 09:03 PM. Reason: typo
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Old 07-01-2012, 09:20 PM
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As long as you are just using one battery in the pump system you will not need to worry about too much voltage or picking up the load difference across the float switch. You could turn the pump on even if the float was up. I think your over thinking it. If you run a wire from the battery to the float switch your covered. If you run a wire from the other side of the float switch to the dash switch the dash light will come on if the float is up. You can use the same wire for manual.
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Old 07-01-2012, 11:16 PM
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Here's a thread by someone else with essentailly the problem , and a solution for the Cole Herseee SPDT switch:

http://www.thehulltruth.com/marine-e...ated-spdt.html ( scroll to Sea Dad's post way down on P. 1)

But check your switches circuits with an ohmmeter or other continuity tester to be sure what you are working with.

There is a diagram that might help a little here in this collection. 1st vertical row 2nd one down:
http://www.google.com/search?q=image...w=1660&bih=857
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Old 07-02-2012, 04:13 AM
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Wire the lamp in the switch in parallel with the pump motor.
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Old 07-06-2012, 09:44 AM
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Changed the jumper to go to #3 (manual) and now it works perfectly. When I switch it to manual, the pump and the light come on. Switch to auto, hit the test button on the pump, and the pump and light come on.
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