May sound a bit crazy but here in Arizona we do what we have to to stay cool. The AC went out om my truck and rather than spending $850 for a new AC system I chose a more economical way, a swamp cooler. I've got a 5 gallon bucket, swamp cooler pad, a radiator cooling fan and a bulge pump. I have one switch for the fan and one for the bulge pump. The bulge pump pumps 750gph or 12.5gpm so I need to be able to turn it off and on so I don't flood my truck.

I have the fan plugged into the cigarette lighter and the pump wired to the battery so I won't be able to just unplug the pump when I park the truck. I was told wiring the switch inline on the negative cable and putting a fuse on the positive cable near the battery is the correct way but I've always put the switch on the positive cable when wiring any other DC related circuits. Which way is best? I just don't want to burn my truck down, it's already to hot here, lol.

 

So long as it's fused, doesn't really matter, though, I would be tempted to switch the power side, so you won't have run away pump if it finds an alternate ground.

 

Makes since, now can I put some sort of variable switch (potentiometer) to control the bulge pump or do 12VDC motors only work on 12VDC?

 

I would expect varying the voltage would indeed vary the speed of the pump, pretty sure that's how DC motors work..... worth a shot at any rate. Keep in mind though, that not running at full voltage might get the pump rather hot......

 

You want the power line to go from positive to a fuse, to a switch, then the accessory, then to ground. Your blower motor in the dash uses a resistor block to cut the power dwn. However, it is built to self cool by drawing air through the motor to cool it while running.

 

I found a DC motor speed controller on amazon (link below), I'm thinking that's what I need to slow down the bilge pump? But it's for brushed motors and I can't find any specs online for my bilge pump to see if it's a brushed motor or not so not really sure what to do?

https://www.amazon.com/gp/product/B0...86E9FNKD&psc=1

 

Just a heads up. The 5 gallon bucket swamp cooler works great. I have the fan plugged into the cigarette light and a toggle switch and the speed controller and bulge pump wired directly to the battery with a fuse. The speed controller slows down water flow perfectly, the only things I might add is a baffle so water doesn't slosh around and a second layer of cooler pad, it may put to much of a load on the fan but it's a 10" radiator fan so it should handle it.