PWM to Solid State Relay (Radiator Fan)

[AlexGSi2000]

Afternoon,

After some advice / confirmation on my plans to add an electric radiator fan to my 2002 BMW Z3 (3.0 M54 engine).

I will be fitting an aftermarket radiator which is thicker than the original, therefore I won't be able to use the standard viscous fan.

So I have some protection, I would like to add an electric fan.

I have two ways of attacking this;

1) Fitting a generic temperature sensor / relay to the radiator (there is a bung for an M14x1.5 temp switch) for on/off operation.
2) Use the standard MS43 ECU to control the fan

My ideal route is to use the MS43 for control as it will be able to modulate the speed via PWM - I can add a temperature sensor to the radiator outlet pipework by way of using a Z4 radiator pipe with the temperature sensor port built in.

I can then pin up the sensor to the ECU as well as the PWM out for the fan relay.

My question being, am I correct in thinking a solid state relay would be suitable for the PWM signal?
I have seen the following relay available by Hella here, would this be suitable for powering say a 120w electric fan from a PWM signal?

Many thanks

[GreenV8S]

You'd need to find out how happy the SSR was PWMing an inductive load - they tend not to like that sort of thing, but the supplier may support it if you add buffer capacitors across the load.

Alternatively, buy a bldc fan with integral driver - they do get a bit spendy, though.

[AlexGSi2000]

GreenV8S said:

You'd need to find out how happy the SSR was PWMing an inductive load - they tend not to like that sort of thing, but the supplier may support it if you add buffer capacitors across the load.

Alternatively, buy a bldc fan with integral driver - they do get a bit spendy, though.

Thanks - over the past couple of evenings I've been mulling it over.
One of the concerns I had was the fan shroud and the effectiveness of a fan if it was just mounted directly to the radiator.

My latest train of thought is to try and find an OEM BMW fan with integrated controller from another model that I can make work with the radiator I have, would just be a case of running the PWM signal from the ECU to the controller, power and ground - sounds much simpler if I can find something that fits.

[Sardonicus]

Try a E46 fan and cowling from a manual trans variant , its got the lot