One radiator will just not heat up, help?

[Hooky]

I have one radiator on the system that has stopped working. When the main thermostat clicks the heating on the radiator does not fire up. Yet if we turn off all the other radiators in the house and leave it on it does heat up and get very hot. We have then turned the other radiators on and it stays hot. Once the system goes off and comes back on again it will not get hot. I am at a loss to understand what is happening. It is a double radiator and the rear part does get slightly warm. It has been bled. The house is only 7 years old.
Can any one shed some light on this and have any suggestions as to how we can fix it?!!
Thanks

 

[gas4you]

Has it got a bleed valve on each panel?

Could be a balancing problem ot the pipes to it could be sludged up.

Try turning the pump up a setting and balancing down the other rads to compensate.

Most house bashers on new build would not even attempt to balance a system, in fact most wouldn't even know what you wre talking about

 

[Hooky]

It only has one bleed valve. How do you balance a radiator? Sorry very new to this!

 

[gas4you]

Close the lockshield valves on the rads nearest the pump more than the ones furthest way.