I have a Trane TAM7 air handler TAM7A0C36H31AA mfr. Date 10/2011. This morning I noticed that the system was running but the fan speed was low. The variable speed fan usually starts at about 80% fan speed for the first minute of operation and then goes to 100% fan speed. The fan would not go to 100% speed. My system has a TCONT 802 thermostat which does not have any kind of dehumidify on demand feature. Setting the thermostat to off and then turning the system back on in cool mode made no change to the fan speed only going to 80%. I tried shutting down the system again and this time turning of the circuit breakers to the air handler and the heat pump out door unit and leaving them off for a few seconds. After turning the breakers back on and setting the system to cool the fan now stages its speeds properly and goes to 100% after about a minute as it should.

This happened once before around late July and shutting the system down and turning the breakers off and back on “fixed” it for a little over a month. I work in IT and am used to having systems which occasionally need to be rebooted but an air handler needing to be power cycled? I’ve read that Trane had some earlier TSB’s for some Hyperion air handlers but those appeared to be with the blower door switch and the wiring terminal block which should have been resolved before my unit was built. When this happened the first time in late July I checked to see if the system could have frozen up and there was no frosting of the lines and the TAM is supposed to have coil freeze protection and is equipped with an EEV.

Has anyone seen this behavior on a TAM7 and any ideas on a permanent solution?