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Re: Electric Radiator Fans - I used one.

I used to have a 320i (1978) and tried using the existing electric cooling fan 
(which was not connected to any power source ??) in place of the mechanical fan. 
I figured it would give me a bit more power.

I wired a comparator to the temperature gauge, and connected this to the fan 
through a relay, so that the fan would come on when the temp gauge read slightly 
over the normal temperature. I built in a bit of hyteresis to the comparator 
circuit so that the fan would not rapidly swith on and off. I then removed the 
mechanical fan, and drove around, carefully watching the temperature gauge.

The electric fan came on when needed and was able to cool the engine in all 
conditions I encountered (Canadian summer - about 80- 90 degrees, with no air 
conditioner radiator to pre-heat the normal radiator air). There was a slight 
but just noticeable increase in engine power. It also ran much quieter, as there 
was no fan noise much of the time. Even the electric fan was quieter than the 
mechanical fan at all speeds but idle. 

I did not measure gas mileage, but I suspect that it should improve slightly 
with this configuration.

My present 535i (1985) has an electric supplemental fan, and I may do the same 
modification to this car.(Incidentally, I have never heard the electric fan go 
on in this car. Maybe it too is not connected to anything).

Jerry Skene

'85 535i       '93 325i