I checked a Trane Air handler unit and found out that only one out of three heating element energized when unit is in heat mode or emergency mode. This unit has only one high limit temperature switch and all heating elements are connected to it. This unit doesn’t have a sequencer but it has some type of relay that looks like the heat pump defrost control relay.
The Air Handler manufacture is Trane. Mode # BWV036A100E1 and the Serial # B06351302, I checked online and could not get any information on the unit.
Would someone please help me advise what to do?