I recently changed from oil heat to gas. All the radiators work in my 2 story home except for one on the first floor, which heats 2 out of the 14 posts. I changed the valve, which didn't work. Then I took it apart and ran water through it and the water went through it OK. When I put it back together, still only 2 of the 14 posts were heating up.
What could be wrong and how do I fix it?