Guarentee its the diverter valve if it's a combi, or the 2 port/ 3 port valve if you have a system boiler (one with a cylinder)
DC Gas, June 2009
one of 3 things,
faulty mid position or zone valve. all depends what system you have, or it's wired up wrong. no doubt it's the valve, also i bet you have only noticed it recently? because you haven't had the heating on.
