The heat strips in my heat pump are cycling 22 seconds on, 7 seconds off when it's in defrost mode or auxiliary heat mode. Shouldn't they stay on the whole time while in these modes?

I suspect it's either the heat sequencer or thermal limit switch or both. Am I on target or should I also be looking at something else?

More than likely tripping a limit due to excessive heat.

Why...

Clean filter?
Clean evaporator?
Clean blower wheel?
Open vents?
Weak, slow running blower?
Weak limit, sequencer....

Start at the top and work your way through the list.

Thanks, Excam.