Last week when I got up for work I noticed the house warmer than normal. I found the electric heat strips still energized. Tstat was set for 70 house was 74. I do hvac work but deal with air handlers, chillers and small boilers, only residential when its mine. Anyway, I asked the guy at Johnstone Supply and he said it sounded like my sequencer was bad. I purchased that as well as a new fan relay, figured while I was in there you know. I installed the new parts and didn't notice that while doing so one of the 24v leads from the trans had come off and was touching one of the line in terms on the trans. Blew the tstat and the heat pump circuit board. I purchased new board and tstat. All seemed well for a few days, until it got colder and the heat strips kicked on, again they did not de-energize, Ive checked the wiring according to the furnace prints but have one thing nagging me, along with the heat strip thing and the two may be the crux of the issue. When the system is off I get continuity between M1, M2, M3 and M4. I get OL between M5, M6, M7 and M8 which is the second set of elements. When all wired are detached the sequencer reads OL as it should. What am I overlooking?

Sounds like you have really had a good time with your own unit. Heaters only stay on for three reasons. The thermostat or thermostat wiring is sending a signal to stay on. The sequencer is stuck on. The signal from the heat pump circuit board to activate a heater to temper the air during defrost is on. Remember the 24 volt circuit took a hit during the short so all parts that were replaced before the short are subject to failure. Could be the sequencer 24 volt side to a hit and only needed to be activated one time or so to fail. Next time hit the sequencer with the plastic end of a screw driver to see if it opens. This is a method of testing that KC13 posted a while back.

Aligator clips and a volt meter always works for me.