The clutch fan shouldn't be having any trouble even in 40 degree traffic, but equally I generally agree that clutch fans were used because they were cheaper and more reliable in the 70s, case in point Volvo switched to e-fans with redblocks for the last few years of RWD Volvo production.
But anyway the radiator thermoswitch is exactly as the name implies, when the sensor experiences temp > N°C, the switch closes, when the sensor experiences temp < (N-5)°C, the switch opens.
You can leverage this to switch an e-fan. You would use a SPST 4-pin relay, you would connect:
- pin 30 to battery positive
- pin 85 to e-fan positive, with the e-fan negative going to chassis/ground
- pin 86 to your ignition coil positive pin (aka pin 15)
- pin 87 to your thermoswitch, with the other thermoswitch pin connecting to chassis/ground
In this way, when your ignition is on (represented by coil positive), and your radiator is hot, the thermoswitch closes, closing the 12V trigger circuit. This energises the relay, which closes the switch between pins 30 and 85, energising the e-fan circuit.
Use any good 30A rated relay, you should also add a 30A circuit breaker between battery positive and relay pin 30.
People act like e-fans are a big deal but they're easy to install and aside from inrush current they only draw a few amps, you can run them fine with stock 240 alternators.
Edit: also, in my experience, they are better in every way. You usually don't need any fan at all unless it's stinking hot, or you're stuck in traffic, or you're hammering it. So you get some performance/fuel economy, but the other big difference is that they are way quieter. You don't realise how loud the mechanical fan is until you hear your car without it.
