I have an old ward floor furnace the pilot stays lit but won't increase flame when I turn up thermostat. I took off thermostat and connected both wires still did not start . I followed the wires and where they connect to unit I gave it a light tap and it fired up. Once I disconnected the 2 wires the flames went down but pilot is still lit. I reconnected wires again but flame won't increase unless I tap unit please help

Sounds like a loose wire connection.