I have a 1997 dodge ram pick-up have mo heat but all hoses are hot thinking that the thermostat is opening. What would cause no heat.

If you live in a real cold part of the world, such as Alaska or Canada, consider installing a radiator cover:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563.html#post262690

Just to be safe, however, you might want to reverse flush the heater core, refill with a 50/50 mixture of the proper antifreeze and distilled water, and purge all air from the system. After that, check the heater control valve. If the problem persists, there may be a blend door problem. Check for a blend door actuator, which may be broken. The actuator shaft should rotate, as the temperature control is changed.

How do I purge the air from the system also where is blend door actuator

On some vehicles, you fill the radiator until coolant comes out an opened bleeder bolt. Otherwise, squeeze the hoses to purge any entrapped air.

Blend door actuators are located under the dash, about where the bump in the floor is. They are approximately 1"x4"x4", with a shaft coming out one side and an electrical connection on the other.

How do I purge the air out of the system

Fill the radiator until coolant comes out an opened bleeder bolt; otherwise, squeeze the hoses to purge any entrapped air. First, you need to find out if your truck even has a bleeder bolt. If it has a degasser system, you don't need to worry about this.

Next. No air in system. All hoses are hot, Blend door actuators seems to be working OK ( when I turn the knob from cold to hot you can feel the difference ) antifreeze seems to check OK. Any other ideals?

If the inlet and outlet hoses to the heater are hot, and not just the by-pass hose, you should have heat. Have you reverse flushed the heater core? If the situation persists, you may need to install a new heater core, which won't be any fun.

How do you tell if the heater core goes bad if it does not leak. All hoses get hot.

You reverse flush it and make a judgement call regarding the volume of flow--there may be too much phosphate scale build-up or corrosion.

Dumb question who do I know which way the water flows through the heater core?

With the heater turned off, start your truck and feel which heater hose gets hot first--that should be the inlet hose. The odds are that the heater core is partially clogged.

I hope that is all there is.