Baxi Bermuda Back Boiler - Hot watter Too Hot

[babaton]

Hi,

Recently the hot water from our back boiler has begun to heat up crazy hot. The hot water tank begins to vent after about 30 mins, the boiler doesn't shut off.

Central heating is fine.

When it first happened the pump began making some horrific grinding noises so I replaced that....but the boiler still didn't shut off and carried on over heating.

Next I replaced the 3 port valve and the cylinder thermostat. Still not shutting off.

Does this mean my cylinder thermostat isn't wired correctly?

or could it be the thermostat on the boiler? but then wouldn't I have the same problem with both HW and CH?

Many thanks for any help.

 

[ianmcd]

post pics of the wiring

 

[gas112]

if its boiler over into the header tank then its more than likely your boiler stat has gone
Reason why its not showing on heating is the rads will be dissipating enough heat to stop it boiling over