When i turn on my heat only cool air blows and never shuts off. can you help

Hi, this Carrier is a through the wall unit am I right? I can give you some ideas as to the cause. In the heat position, and blowing all the time cool air, the thermostat can't get satisfied to cycle off. This is a heat pump, so if you are able, you need to see if the compressor is running by listening. Turn it up on heat and see if you can hear it kick on. If not, and if you are handy at all, and can get to the compressor area, there is a run capacitor that starts it. It is mostly chrome, plastic maybe, oval and looks like a small sealed metal or plastic can with 2 to 3 wire terminals on top of it. Each terminal is marked C, Hermetic, Fan if 3 but you should only have 2 wires. Just look it over to see if it is leaking oil, or it is swollen looking you will know. It may be a different shape also.Anyway, if you see any of this, it has to be replaced. If not, the compressor could be at fault. If its fine in cooling and running, that narrows it way down. A faulty reversing valve not switching over to heat. If the compressor does run and cool in cooling, forget the first steps I told you about. We know it is in the reversing valve and must be taken in for repairs.Special equipment is used to R&R this valve. I wanted to give you a longer explanation in case the compressor is not on and to check these if you are able. Let me no what you find so we can solve this.
Sincerely,
Shastalaker7
PS Turn it to cooling 1st and if it is cooling good, we know it is the reversing valve.