AO Gold Member
Join Date: Jun 2007
Location: United Kingdom
Check that the fan speed increases after about 95°c, if it doesn't then the resistor is kaput. This can be cheaply worked around by connecting the two wires together with a large 30 amp fuse. The resistor is found on the fan mounting.
It is also quite likely caused by a knackered radiator - they don't last long on the 156. Have a look at the state of the core, if it looks like a party popper has gone off or there are parts missing, there is your problem as it will block the flow of air.
If money is tight, as a temporary measure, you can pressure wash the copper core off to allow airflow through the radiator (you'll need to remove the radiator first) - probably not recommended by many on here, but it kept my Twinny running whilst I was strapped for cash!
Chances are that if your engine has got that hot, it will have killed the thermostat. Does it still get to 90° fairly quickly? If not, you'll need a new one, but at £30 and half an hour to fit yourself, it's a fairly cheap and easy repair.