I'm thinking you're talking about a fan switch not a thermostat.
The relay supplies the heavy voltage/amperage to run the fan and the fan switch just provides a ground for the relay. The relay also uses inputs from the A/C to turn the fan on. Do you plan to include these inputs too?
I bought an adjustable thermostat that can handle 16 amps and am wondering if it will handle the fan current directly or if it will have to use a relay also. This is what I got, cost me all of $7.00 delivered:
Figured I would just put it up against the input coolant line and wrap some insulation around it, put the dial on the dash some place so it can be changed from inside the car, should be dead easy I think. Larry
I'm thinking that all the cooling system components between the engine output and engine input all contribute to the cooling process. I'd be inclined to locate the sensor on the input line to the engine so that if the coolant returning from the rad is too hot the fan comes on. A location not immediately adjacent to the engine would likely be better so that engine or engine compartment heat don't affect the sensor. For all it matters, maybe the rad output line wouldn't be much different.
When I measured a rad fan, through an amp meter, it peaked about 80 amps for a split sec to start it spinning and running it was about 18 amps. I tried a couple of fans and got the same result. All stock fans. results may differ but this is what I showed, even used two different amp meters.
Originally posted by sardonyx247: When I measured a rad fan, through an amp meter, it peaked about 80 amps for a split sec to start it spinning and running it was about 18 amps. I tried a couple of fans and got the same result. All stock fans. results may differ but this is what I showed, even used two different amp meters.
Factory Fan motors is likely so... Did you check volts at motor? Volts does matter... Bad power/grounds will make motor to draw more amps, a common problem in old cars. See my Cave, Electric Motors
What kind of meter(s)? Inductive or shunt. Hooking up a shunt can cause volt drop and motor draw more amps to make up the watts. I would test but my meter has 10a max shunt.
# of Watts I post came from ACdelco web site for new ones.
I got an amp meter(gauge) and all the current went through the gauge, I used a battery charger to provide power. This was all hooked up just for testing. one test I used the gauge meter and another I used a Craftsman engine analizer with an amp meter built in. and I tested a few different fans all had the same results. (All stock fans)