The York installation manual states that the full auxiliary resistance heat is activated shortly before a defrost until shortly after so as to compensate for the cooling during the defrost cycle.

I find that I get very cool air (60 degrees) during the defrost cycle. In tracking the reason I find that only one (W1OUT) of the two (W1OUT, W2OUT) resistance heat signals is being asserted at the defrost control board with the consequence that I am only getting 5kw of resistance heat rather than the expected 20kw.

To test that the wiring from the defrost control to the air handler is correct, I switch to emergency heat and observe that the full set of resistance heaters are correctly activated, showing that: the defrost control board is capable of asserting both control signals (W1OUT and W2OUT) and that the wiring to the airhandler is indeed correct.

I've observed this condition for two years now - and as luck would have it the control board has been replaced three times (thanks to York's inadequate protection from snow infiltration design) , otherwise that's what I'd suspect.

I've recently installed a house power monitoring system so can observe KW consumption minute by minute - so it's not imagined that the full resistance heat is not coming on...

The York documentation has many errors and omissions, so I wonder if there is some secret that one needs to know to get the defrost cycle functioning correctly.

My unit is 3.5 ton, with matched handler, 4 years old.

Is this a known issue or something I've overlooked ??

thanks, Dan S .