Heat Pumps and Electric Heating - Trane XE1000 defrost timer

Can anyone give me a tech narrative of how the defrost timer works in the XE1000. My old unit had a mechanical timer that ran below about freezing and worked very well for 22 years. It would defrost needed or not but most of the time it did. The XE1000 timer doesn't do it when not needed but the same when it is needed. Sometimes I have to remove cover and force it to defrost. Would it be safe to install a key lock spring loaded switch on the fixed cover? I am looking for maybe one of the old timers. Should have kept the one out of old unit.

Modern heat pumps normally don't do simple timed defrost. They either use temperature triggered defrost or a timer in conjunction with a temperature triggered defrost. The timer is just to make sure defrost cycles don't come too often, the temperature sensor is what determines if a defrost cycle will happen.

Can anyone give me a tech narrative of how the defrost timer works in the XE1000. My old unit had a mechanical timer that ran below about freezing and worked very well for 22 years. It would defrost needed or not but most of the time it did. The XE1000 timer doesn't do it when not needed but the same when it is needed. Sometimes I have to remove cover and force it to defrost. Would it be safe to install a key lock spring loaded switch on the fixed cover? I am looking for maybe one of the old timers. Should have kept the one out of old unit.


Sounds like you did , a new Trane ?

Yes older ones ran off 30, 60, 90, second sensor ,which you could usually breath on and fail :wall: and defrost timer , newer ones solid state controls.

Thanks for the replies on the defrost timer. I have done some digging and the sold state ones work on a similar theme. There is 2 sensors, one is ambient and the other in a well at the bottom of the coil to stop the defrost when the coil is clean. The on board led blinks about once a second but if you watch closely it will blink rapidly now and then. Trane Techs should have the adapter that slides over the led and with a laptop and Trane software it can give the status of what is going on. Also in my documentation I have a list of both resistance and voltage readings at the outside temp. The plug on the board is a molex type and famous for bad connections. Generally speaking I was told if the led is blinking once a second and does the extra blinks it is most likely OK. I have friend that is going to get the info on how to make the photocell which plugs to a usb port and get a copy of the software. It is a very small program but most Tech don't know about this. Most of the time when there seems to be a defrost problem they reseat connectors and it if continues replace the board. Temps are starting to drop and will see what happens. I have done all the usuals.