This isn't too hard to do. You need a relay with a 6VDC coil that also has
contacts rated high enough to carry your 12 volt water pump current. The
whole assembly can be housed in a 1X2X3 project box from RadioShack.

The relay coil will be wired into your Coleman heater - I assume you know
where.

The relay contact will be wired across whatever turns your water pump on and
off now.

Thanks,
Tom Hargrave
256-656-1924

Our Web Sites:
www.kegkits.com
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www.andyshotsauce.com

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@GERRY.VANAGON.COM] On Behalf Of
Troy
Sent: Saturday, February 27, 2010 3:37 PM
To: vanagon@GERRY.VANAGON.COM
Subject: 6 V power supply to activate 12 V circuit-- possible?

A question for the electrical gurus out there:

I have a Coleman hot water on demand that uses a 6 V battery to operate, and
would like to set things up so that when I activate the Coleman, it starts
the westy's 12 volt pump. My eventual goal is to have hot water outside the
van using the on board water tank and pump. I could convert 12 V to 6 V to
power the Coleman, but don't think it would have enough power to operate a
pump with adequate pressure for longer distance, and this would mean two
pumps, two lines, etc. So, trying to make the 6 V circuit power a 12 V
circuit. Is this possible? Some type of switching relay perhaps?

I have the necessary connectors, etc. It's a project I've been thinking
about since last year and would like to make it happen before camping season
this spring. Since I no longer use the city water connection, I'm thinking
of putting the connectors in behind that utility box or perhaps something at
the rear of the van. Since I have an extend a stay on my propane tank,
something on the side of the van might be nice to be able to use the
existing propane source as  well. I have hooked up barbecue grills and such
with the extend a stay, and it works pretty nicely.

When I finish this project I will post the pictures to a website for
everyone else to look at. I'm sure others would be interested in such a
setup.

Thanks,

Troy