upstairs radiator not working - all others are ok - valve on one end Therm controller on other - took a spanner to the valve and ensured open - still will not come on - what could the problem be?

  • Is the radiator on it's own pump? or part of a circulation loop using convection to move hot water? Have you tried bleeding out air that might be there? Very likely you have some air in there. Again, a few pics would help, esp of the connections. – George Anderson Feb 21 '20 at 15:52
  • Is this a steam or a forced hot water radiator? – Carl Witthoft Feb 21 '20 at 17:00
  • Hello, and welcome to Home Improvement. Unfortunately, we'll need more info before we have any chance of helping you. Please take our tour so you'll know how best to participate here. – Daniel Griscom Feb 22 '20 at 14:19
  • Did you ever get this resolved? If so, please give a check-mark to the answer or write up your own answer explaining what you did to get it fixed and give yourself a check mark. That will help others with this kind of problem know that this has a resolution and is a good place to look for their answer. – FreeMan Aug 20 '20 at 15:58

Possible reasons:

Loss of heating water

  • Failing safety valves
  • Failing automatic air release valves
  • Tenants or house cleaners misusing (radiator breathing) valves as water supply

Leaks in the heat exchanger or pipe system, valves or radiators

Expansion tank

  • Incorrect pressure setting in air chamber
  • Failing membran
  • Leaks

Air in the system

Heating water circulation pump:

  • Stucked shaft
  • Failing phase capacitor
  • Turbine eroded by sand/rust/hard parts, cavity problems

Blocked (bypass/thermostat) valves, the tiny rods/shafts of thermo valves are prone for getting stucked

Input/output pipes of radiators/radiator valves mixed up

Blocked pipes (metal/rust parts/dirt)

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