Old analogue thermostat not cycling

[paulfedex]

(05-21-2017 20:35)davidbrady Wrote:  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?

Hi David,

Thanks so much for the info. No short-term at all. They just run all the time or none of the time. Interesting about the fluid in the capillary tube. Bulbs and tubes are there, but don't know about the fluid yet. Yes, they have always run a bit warm. The faceplate seems to act as a heat sink. So, this AAP place stocks these parts?