Wall heater does not work!

I have a tri-plex in CA built in 1949. The 1 bedroom units have small heaters built into the wall. They are not very efficient, if they work at all.
I can not get one of the units to even light? I've replaced the gas valve and a thermocouple. I even blew out the gas nozzles and the burner area. Still I can't get the burners to light. The pilot light works but that's all. The place I bought the valve from says that's all I should need. I'm not sure of the model numbers If they're there, they have 30 coats of paint over them.
Any suggestions?