There are a wide range of cars that have thermo switches mounted in the
radiator to do just this, what's wrong with copying the circuit from the car
you pull the switch out of? They will already be suitable for 12 volts and
are fairly weatherproof.

You can also use the standard thermostat from a hot water system on 12 volts
and they would carry enough current to stitch your fan. Might not have the
vibration resistance if you wanted to use it on a car. They would also have
to be mounted dry outside but in contact with the meal surface of the water
holding "tank"?

Cooking thermometers can be mounted to some items and there are ones that
hook up to certain model ovens to turn off the element and maybe ring a bell
when the roast is cooked.

They will have a mounting that can be copied or transferred to almost any
tank you might want to use, or inline with a plumbing fitting.

Fishtank heaters have a thermostat and can be rewired to suit. There are
other options,

Hope this helps,
Peter



I want to make a electronic controller to turn a fan(3" muffin type)
when water temp reaches a certain temperature. I know they make water
proof or submersible thermistors, and there can't be too much to the
circuit as one company makes such a fan but its sensed with air temp
and I want water temp.......Fans are all 12 volt DC.. I owuld like to
turn on fan when water temp reaches 81 deg or so and off when it gets
back to about 79 or so degrees.

Any links on circuits etc appreicated or on how to figure out what
thermistors are needed.
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