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Adding frest water pump switches

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Bruce Benson:
Matching the question to the system on my coach has proved an interesting puzzle.  Like many with my generation of coaches, I have no wiring diagram to refer to and can only surmise how it is wired and built, then follow wires to see how good a guesser I was.  

My 4 water pump switches are rocker type but are temporary contact, meaning that they rock to the on or off position but always return to a neutral position when released.  I can turn on the pump at any of the 4 switches and turn it off at any of the 4 switches as well.  

If this system is done with relays (which I fully understand) rather than transistors (which are P.F.M. and never seem to work like I think they should) it would require two relays to make it work.  

The "on" relay would latch once it was energized by rocking any of the switches to the on position.  The latching would occur through the making of one of two sets of contacts in the relay which forms a sort of endless loop, powering the relay through itself.  The other set would turn on the pump and the indicator lights at all 4 of the switches.  

The second or "off" relay would have a set of made contacts that would become open when the relay was energized.  These contacts would be wired in the latching loop that is holding the "on" relay down.  The off relay would be energized by pushing any of the 4 switches to the off position.  This would then open the contacts in the latching loop and release the "on" relay (by breaking the "endless loop") turning off the pump.  When the switch is released the "off" relay would return to static which leaves everything off and ready for the next time the pump is turned on.

Interestingly, off on the switches is really not off.  It is off when it is centered.  When the top is pushed one current (to the "on" relay) is activated, when the bottom is pushed a different current (to the "off" relay) is activated.    

For my system that would mean 4 wires to each of the pump switches, one for power, one to the "on" relay, one to the "off" relay and one to ground the indicator light.  It would require 2 relays (Radio Shack), one with two sets of normally open contacts and one with one set of normally closed contacts.  The indicator light could be connected to the wire going to the "on" relay as this wire would remain hot when the relay is latched.  

Bruce

MarcRodstein:
I also have an '03 Monterey and I am thinking about the same mod. The preferred way to do it is to install an Intellitech Monoplex Water Pump Switch. This is what is used on most of the higher end coaches. It is not expensive. See http://www.intellitec.com/PDF/5300145.000.pdf

If you do it, please let me know how you wind up running the wires. That's what has put me off from doing it so far.

Joel Ashley:
Good explanation, Bruce.  I wasn't up on latching relays.  But sounds like a lot of wire involved.

Thanks.
Joel

Tim Westman:
If you need a latching controller I have a couple of spares from my '05 Monterey.  Both are in working condition and new.  I would be more than happy to pass them on if you can use them.  I can be reached at 231-730-0346.

Gerald Farris:
A latching relay system can be wired very easily with 2 wires to each switch by using a pulse type latching relay like the Magnecraft 711 series relay. In a pulse type relay the contacts transfer and reset when a unidirectional pulse is applied to the single coil using two (2) control wires. Therefore with this type relay all that is needed is a 12V wire through a momentary switch to supply a 12V pulse to the relay to change it's state from on to off or off to on.

Gerald

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