At last I'm making real progress on getting my '93 240 wagon back on the road.
The radiator that I have installed is from a 740 (kindly donated and has a switch built into the rad.
Can this switch be used to activate an electic cooling fan in a similar way that I' ve seen 850 fans mounted onto 240's?
If so, how? I have an 850 fan and shroud and the 2 stage relays from 850. I don't have the input plugs for the relays. Can they be purchased somewhere?
Cheers
Short answer is “yes” you can do what you want to do. 
Longer answer is that I’m not sure how. I don’t know what that switch is for, it may actually be a temp sensor that the ECU uses … others may know if there’s a separate module or something which can use the output from that sensor independently of the ECU.
Mebbe have a look around at aftermarket kits, what sensor(s) they can use to trigger the switch that turns the fan on & off?
I am not a fan of adding an electric fan to a vehicle that was not designed to have one.
It’s similar to me taking something that the manufacturer thought hard about to design and engineer something to work better than anything else and changing it because I must know better. I like to leave those systems alone, as long as they work correctly and do what is asked.
I’m afraid I cannot offer any other help regarding your question
ramrod I am not a fan of adding an electric fan to a vehicle that was not designed to have one.
Only because they were more expensive back then.
Actually … given 740 runs pretty much the same cooling system, it seems pretty weird to me that a ‘93 240 didn’t have an e-fan!
Problem with those clutch-fan thingies is you’re relying on a part which was only available for a car which went out of production over 30 years ago, but with electric a lot of parts you might need to replace are generic.
Hey are ramrodfunk & ramrod related?!
I guess one point, however, is that there’s not really any gain from doing the conversion if your existing cooling system’s fine. But if you DO convert it for some reason, don’t neglect the fan shroud, it’s more critical than you might think.
Fortunately, the clutch fan hub is available new.
ramrod Fortunately, the clutch fan hub is available new.
While that's exactly what I'd fit if I had a standard engine which had one of those, what I'm wondering to myself about ALL of these parts is "how much longer?" ... when I first started taking Big Red to the mechanic I'm still using, probably about 18 years ago, anything & everything was available from the local parts place ... needed inner tie-rod end (I think?) for pink-slip last week and it needed to be flown up from Melbourne (the alternative being CCP parts of a brand which he said I'd need to replace in about 2 pink slips' time - even though it'd probably only have done 2000km on the part).
But that's completely off topic.
Can be done, fairly easily. Has been done LOADS of times. Spend some time searching the forum for examples, there are a few. The methods, and there will likely be more, are:
As for running it:
Relays:
My suggestion: find a 940/960 fan and shroud WITH the wiring harness and relay uncut - wreckers like cutting things, you need the relay with the three connectors in it (one to the fan uncut, one to the battery uncut and one to the ECU - cut this one). Grab an ECU from a late 940 or something that had an electric fan (the late ECU will work fine, they are all mostly the same). Run the two wires from the ECU to the relay. Remove the wobble weight from the waterpump (aka mechanical fan).
As for a short answer to the 'can the push in temp switch be used for running an electric fan' then generally No.
I've got a Davis craig stand alone fan controller I was using while diagnosing a cooling system problem. Worked perfectly with a 740 pusher fan and only cost $50 off the FB marketplace. It uses an included temperature probe that goes between the radiator fins.
Once I solved the problem I returned the car to mechanical fan only which I found much more effective than the mechanical & electric fan setup.
Forg Lol, not related.
In both my 240's, on hot days in Sydney, the clutch fan seems to struggle and forget about air con especially when in traffic.
Do they overheat? If so what temperature? Do you have an infrared thermometer?
How old is the radiator?
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:
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.
