The sequencer contacts on the emergency heat is stuck on and will need to be replaced. Look at the numbers on the base of the sequencer and buy replacement. Turn all power off and replace leads one by one to new sequencer. I remove the base plate screw on the old sequencer and screw the new sequencer in place. Change wire by wire. Be aware to check the spade connectors are tight on the new positions. Most new spade terminals are thinner than older and the spade connector female side needs to fit snug. If necessary the female side can be squeezed with a plier until it installs snug. Renew any connectors that are burned or badly corroded. I would recommend calling a professional air conditioning tech if you have the least bit of hesitation to working on the equiptment.
Hope this helps.