2 speed engine cooling fan wiring

I'm looking for some advice on hooking up a 2 speed cooling fan in my hotrod. The fan I have has 3 wires, a ground and 2 positives. Low speed is activated by one positive wire and high speed is activated when both positive wires are connected. I will be controlling them with an ON-OFF-ON toggle switch and 2 relays. I've tried to lay out a schematic of how I think the wiring should look.


I also have 2 variable temperature switches (the kind with the temp probe and adjusting knob) that I may use to automatically turn it on, one set at a higher temp than the other. I will keep the toggle switch as a backup in case of failure of the temp switches. That schematic would look like this


I may omit the second variable switch and just manually engage high speed on demand with the toggle switch. I may also decide to wire the positive inputs on the variable switches to an ignition switched source so the fan will not run when the car is off. Do my schematics look like they will work? They seem fairly simple but is there a better way? I'm not too sure what diode I should use either. Thanks for the help!

It looks good to me. What is the purpose of the diode? Do both low and high speed wires need to be powered in high? If not, you can eliminate it.

I would leave the variable temp switches on constant power. Most cars will allow the cooling fans to run after turning off the engine. If you are worried about the battery draining, you can install an automatic battery cutoff so if the voltage gets below a certain point it will kill power to the car.

-------------
My ex once told me I have a perfect face for radio.

Thanks for the help. Yes both power wires need to be connected in order for high speed to activate. The diode will prevent the high speed relay from energizing when low speed is activated. I'm not sure what diode I will need but I don't think it needs to be very large since it is only on the trigger side of the relay.

If that's the case, a simple 1-amp rectifying/switching diode will work fine. I used to buy them in a 25-pack at Radioshack.

-------------
My ex once told me I have a perfect face for radio.

I have 2 diodes on hand and would prefer to use one of them if one will work, however I don't know what the markings tell me. Here's a picture of them with what is written on each of them.

Either one should be fine. If your meter has a diode test, touch your negative probe to the side with a stripe. The other side goes to positive. You should get a reading/audible tone. Reverse the leads and you should get no reading/tone (it may say OL).

If your meter doesn't have a setting for this, you may be able to take a resistance reading. Again, stripe to negative, other to positive, you should get something. The other direction, you shouldn't.

-------------
My ex once told me I have a perfect face for radio.

Thanks geep, I finally got the fan installed and everything works as it should!

I would recommend using the automatic temp sensors. I built a single speed switched relay setup on mine, and after the first time I forgot to flip the switch on and my motor got to hot I quickly installed a temp sensor to turn it on/off for me.