I realise this is a very old thread.. but had this exact problem this eve - total lack of info.., anyway - I plugged in following the same layout of the spades -
numbers in brackets are the SFB191 pins:
31 to (1) / 49a to (5) / 49 to (2)
*This was on an 1983 ex army Series 3 109.. turned out my problem was a dirty switch after all! - the SFB191 worked fine., as did my old SFB164 after cleaning the switch.
Pin out for SFB164 being:
Lucar/Spade Terminals (31 earth/ground, 49a direction indicator supply, 49 ignition controlled supply, C2 trailer warning lamp)
Bri.
