Electric Fan Switch

[Alpina99]

I'm just spending a few hours preparing some of the smaller looms for my eventually finishing the car & fitting an M50,

I've just been looking at the thermal switch fitted to the E36 rad & noticed it's got 3 wires, brown, purple & black. I assume this is for a twin speed fan ?

A continuity test shows that, taking brown as the "feed" the purple powers up before the black so I'm assuming purple is first temp & black second,

AS my fan is single speed, should I use purple or black for the "switch" ?

Any ideas ?

[Alpina99]

Ok Will,
Thanks for that, it is an E36 one so I'll look to change it,

[DanThe]

When it switches from 80 to 88 it drops the feed to the 80, so you need to use either the high temp pin, or both to run a single speed fan

[Alpina99]

Thanks Dan,

[booomer]

When it switches from 80 to 88 it drops the feed to the 80, so you need to use either the high temp pin, or both to run a single speed fan

Does this mean the fan will come on and go off at 80 degrees?

I know most people view the 88 degree thermostat as being preferable over the 92 but the 92 is what i have, will this be ok when using the 80/88 degree rad temp switch?

[booomer]

single speed fan will come on at 80 degrees and go off at 88 degrees.

It will be ok as the thermostat will control the flow of water through the radiator. The fan will just stay on longer and cool the water down more in the radiator with the cooler temp switch, which is a good idea as it gives you reserve cooling capacity for stop/start traffic.

Ok, i can't really picture how that will work. Don't you want the fan to come on and stay on untill the temperature drops below the threshold rather than going off at 88 degrees???

All i basically want to do is have a single speed fan that will come on at a suitable temperature for my thermostat/rad temp switch

[booomer]

single speed fan will come on at 80 degrees and go off at 88 degrees.

It will be ok as the thermostat will control the flow of water through the radiator. The fan will just stay on longer and cool the water down more in the radiator with the cooler temp switch, which is a good idea as it gives you reserve cooling capacity for stop/start traffic.

Is this actually the case? i was under the impression that the fan comes on and then goes off once the temperature has dropped?? i.e. comes on at 88 then goes off at 80??

[booomer]

when i drive my car hard or sit in traffic the temperature climbs up to 3/4. the fan cuts in and does bring the temp down but to far enough and it seems to cut in too late. i'm using the 80/88 degree switch as above and the lower temperature thermostat so i cant really see why this is happening

[magpie]

what size fan are you running and is it moving air in the right direction ?

[DanThe]

If the fan is not cutting in until 3/4 on the gauge then you must be working from the 88 switch, this means the whole of your cooling system is above 88 degrees when the fan comes on, and is still climbing before the coolant in the radiator has dropped to a low enough temp to cool the engine. So I expect your engine temp will be above 90 degrees before it starts to cool again.

Ideal situation is where the coolant in the radiator is cooler than the running temp of your engine at all times, this allows the thermostat to control the engine temp easily and quickly

[Motorhole]

Been thinking about this as I want to move away from the E36 fan and use a slimline puller instead to move the weight backwards and to free up more airflow to the rad - and to reverse the self-tapped, hacksawed cowling pikeyness of my current arrangement!

If I've got it right, any fan could be made a two speed fan. The ground connection from the fan remains as is, but split the power feed into two; one direct to the high-speed circuit and one via a 50-Ohm resister (of appropriate loading) to the low speed circuit. I was planning to take the resistor off the E36 fan and wire up using existing 3-pin connector to just plug into the existing loom.

[DanThe]

Its only of benefit for a road car Lewis, full speed ahead is what you want for track.
Ive got a 12 inch fan mounted on the back of the rad on my track car now, you might have seen it at Oulton, cant remember TBH but it works fine

[Motorhole]

Thanks Dan, that makes sense. Although for the nest year or two I foresee myself still having to drive the car to/from track events which sadly means sitting in stop/start traffic on the M6 or M62/M60 whichever way I go

Will eventually source a mode of car transport which will allow me to make the car a little less compromised for track use

Still want to get that S52 rad sorted soon too!