I have a small 28cm fan assisted roof vent, similar to the link below, fitted to my motorhome. http://www.leisureshopdirect.com/ca...urbo_Vent_28_Rooflight_12v_White.aspx?aff=122 The vent works well and shifts a lot of air. The main problem is that the noise level is far too high and becomes a real nuisance. I would like to reduce the noise level by reducing the speed. I could do this (I believe) by fitting a series resistance either permanently of withe the possibility of switching it out. Anyone had any experience with this modification and can offer advice?