Hoover A8578 washing machine boiling

[uncle tom]

I have a Hoover Ecologic model A8578 Washer Dryer which I guess is about 15 years old (maybe more) but has had less than 5 years average usage.

Now when I use to washer the water boils and steam pours out.

Has the thermostat has failed (although I understand some machines use thermisters)? I don't which mine may have. At the back the drum cylinder has three fittings, one is the clearly the heating element, and one presumably the thermostat, but what is the third (could it be another thermostat, they are connected together with one white wire).

Or could it be the timer, I understand some washing machine sense the water temperature and when it reaches a certain point run the heating element on the timer for a specified time calculated to heat the water to the various programme temperatures.

Thermostats appear relatively inexpensive, but it's not economic to replace the timer I think. Are thermostats colour coded, one of these fittings has one green dot, the other two yellow dots.

Any ideas what is the problem, or how I might diagnose the problem? I don't want to waste time and money keep replacing parts until I stumble on the faulty components?

Thanks,

T