RAMBo Fan 0 connection (no replies)

I am using a Rambo (v1.2 I think) and having some difficulty with my Fan 0 (bed fan). Command M106 S* does seem to control the output to the fan, but the Fan only seems to work if it is between about S245 and S255 and only works down to about S245 if it was already running. Below S245 and the fan may "twitch" a bit after M106 commands, but then stop almost immediately. Can someone tell me is there a specific type of fan that is needed? Brushless? Brushed?

Thanks,
Dave C