my heater only blows hot dispite the control being at cold?

It might be the duo-valve which is under the bonnet and close to the driver on a right hand drive car.
It has one heater pipe going in from the engine side and two pipes that exit towards the passenger compartment.
On the top are two solenoids.
If this is not getting power with the ignition on it will revert to full hot.
If possible check with a volt meter and look at the fuses.

Mark
March 2008

had the same problem with my 97 sprinter blowing hot air all the time even with the dial turned to cold checked the cable the controls the matrix valve seemed ok ended up ripping out the complete dash to get to the heater matrix it ended up being the matrix valve rubber inside the valve it was leaking still allowing hot water through had to end up buying a new heater martix valve which has now solved the problem

walter
March 2008