240/740/940 (probs others) e fan conversion switch mount

BarelyRunning

I couldn't think of how to title it better, very open to suggestions. I made this today, just a SAAS (generic ebay one will probs work) water temp sensor adapter, with a hole drilled and tapped for an M22x1.5 switch (most common 2 speed switch), leaving the original 1/8npt hole in place for a temp sender or T piece etc, extra pic with pen to show there'd be clearance for a sender.

I made it with hand tools, so it's not perfect, but some thread sealant will fix it.

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jamesinc

Thanks for sharing. I have done a similar mod on a couple of 240s, one issue I noticed with my setups at least is that the sensor is quite influenced by ambient temps. So on the highway in cold weather I had cars ironically overheating as the sensor was being chilled by the ambient air. I solved by putting some pipe insulation foam sleeve over it like this

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Ravanelli

I have done a couple of these. I always mounted the switch on the top hose?

VolvoHordz

Ravanelli which hose is the 'right' one to put it in is much debated. Been around 240's with either configurations and both worked fine.

You would typically have a slightly lower switching point if in the lower hose (which is the return to the engine), and I have made the choice of which hose in the past based solely on what switching temperature I could readily get at the time.

My 2c worth, the lower hose makes more sense as if or not the fan needs to run is dependant on how efficiently the radiator is working, so best to be measuring the outlet temperature. Also temperatures should be more consistent and hence less likely to result in fan oscillating on and off.

dmc

top hose measures temp of coolant coming out of the engine - great for a gauge etc.

bottom hose measures temp of coolant going into the engine. if it is a good temp them leave it be. if it is too hot then need to do something.

eg. at 100km/h radiator is super cooling device just as it is. coolant going into engine is cooled through radiator and everyone is happy.

2nd eg. when stationary there is little air moving across the radiator and coolant into the engine/out of the radiator would be as hot as it was entering the radiator. a fan can help this.

for a fan switch bottom hose or cool side of the radiator is the go.

Oh, and Volvo do it that way too. (and James from that photo).

FWIW i have found my various 240s cool them selves from about 65-70km/h and up. below that a fan is needed. at tech (late 90s) we were taught that 40-50km/h was the tipping point.

jamesinc

Yeah my wagon mostly only switches the e-fan on in traffic. Never comes on on the highway unless it's like 40 degree weather.

Anthony

All very good statements.

From my Volvo / Haltech experiences Im searching for the best position myself. I had sensor down the bottom hose till the tuner said use another reference and thats the head temp.
Some ramblings but no answer.
I have a digital temp readout so know what’s happening at the head before the thermostat.

The cyl head is the hottest place and thats where Volvo has the temp sensor, so with a normal Volvo running around lets say its 95 degC.
Now down at the bottom radiator hose its only say 45C.

As lately im using the cyl head temp, the thermofan stays on for a long time and it loud.
As soon as the engine is turned off the cyl head temp sensor gradually rises towards 100 as no water is circulating.
The only way to change that is to keep the engine running till internal head temp drops from the cooled rad water.

I can manually turn the thermofan on when engine is off but i found that to be a fool’s paradise, as without circulation of water through the block/head all the fan is doing is making the radiator cold, not the engine!

Now I can see how an electric water pump would be the perfect answer as you could still circulate water when engine is off to get the head temp down (but what if the electric pump fails, your screwed compared to a mechanical pump).

For the record i use an 82C thermostat (track use) vs std Volvo redblock 87C. And a smaller custom PWR radiator.

dmc

There should be a switch in the radiator for over temp, even with key/engine off it will engage the fan to cool it down (the radiator, not the engine though better than nothing). It is the pop out one that has no thread. One of my cars uses the late LH2.4 and efan (from a 940 I think) with the switch in the head, it is a nightmare. I had to go to an 83 deg thermostat to keep it usable, the 89 and 92 were dangerous.

The theory behind the bottom hose is that it takes into consideration the function of the radiator. At full noise and 110km/h the head will be hot, though the radiator will be working well, an efan is pointless here. It is just sucking 30 amps of power and slowing everything down - and lets be honest, with very little power to start with every bit helps (in may cars anyway)!