BoatBud.....There could be several things going on. I see you live in Maryland. If you're trying to get it to heat up in the cold spell you're having, it may not until it's driven for a 1/2 hour or so and even then may be weak.
You should also listen to see if the door on the heating unit is opening and closing, by listening for it on the interior side of the passenger's dash. Run the engine for a few minutes and then turn it off and manipulate the A/C and heater controls. You should be able to hear the heater door open and close.
I'm not sure if that era coach still used vacuum to open and close the heater door or if it was electronic. My guess would be electronic, which would be built into the actual controls. You also need to get under the hood and see if the heater control valve is opening and closing. It will be the valve with heater hoses running to it. You should be able to see if an arm on the valve changes position from A/C to the heat mode. Sometimes you can take the control arm off of the valve and operate it manually to see if it's frozen (rusted) or not.
If you have a trip planned, you can run the heater in the coach while driving to keep you warm, but the windshield may be an issue.