Old analogue thermostat not cycling

[davidbrady]

Hi Paul,

You'll probably need to get AAP on the phone. Sounds like you have a faulty thermostat. The early tstats were known to fail because they switch 120VAC and they get hot. They also have a 10' long capillary tube terminated with a large temperature sensing bulb that's mounted in the return duct. Could you have damaged the tube some how? Perhaps you can sight down the return duct to find the bulb to make sure it's still connected to the capillary tube? I think the capillary tube and bulb contain a liquid that expands and contracts at normal operating room temperatures. Sounds like the liquid leaked out making the temperature control ultra sensitive. Does the compressor short cycle?