Is it common..even when the heater is working

Check your flex tubing in the heater lines....had the same problem and when I checked under the front cap hood I found one flex line disconnected allowing outside air to come through the heater vent.....reconnected (and clamped) the flexline...made a big difference

The big air leak in ours was the whole heater/AC unit--three of the four sheet metal screws that were to hold it in place weren't. Not just weren't holding it in place, they weren't even there! The tech was able to lift the whole thing several inches. A gaping hole through the firewall. Much better now it's riveted into place.

I took mine out in cold weather last weekend and was cold while on the interstate but noticed that I was much more comfortable when I got onto back roads with lower speeds. This definately points to air infiltration and my prime suspect is one of the slides. If you notice any patterns like that it will help diagnose the problem.

I have seen double layer covers advertised for Fantastic vents. I suspect that putting those and external vent covers on will help keep the heat in. If anyone has feedback on the double layer covers I would love to hear it.

Don't forget that RV fridges vent the compartment they are in to the outside. Be sure to check the walls for insulation and for drafts around the front.

We've done both heat and air in our 2002 Itasca Sunrise 32V. When it's just momma and I we rig a blanket behind us to keep the hot or cold air just in the cab area. However when we have the grandkids, we run the generator while were driving and run either the air conditioners or the heater for the coach. Seems to work just fine.

Wait till you have some wind. Run the furnace. Go around with a can of great stuff and start sealing up anywhere you have cold air blowing in. I would expect you to use up 2 cans.

As far as heat from the engine, as long as your gauges say it is up to temperature, you should have pretty hot air coming out of the heater. May not be enough to heat the coach, but it should keep the front warm. I guess that is one advantage to a gasser is the engines run warmer and can put out more heat. We camp in single digits, but the engine heat will take care of the whole coach when driving.

Run the furnaces. Ours needs regulating though. It will get it steaming hot then shut down due to where the register is behind passenger seat.
We run the rear furnace a few degrees warmer and that keeps the front from coming on as often. that and the dash heat and we are reasonably comfortable. If it is not too cold run the generator and the heat pumps.

I agree with Sowego, I bet you have some air leaks going on, especially if you have a drivers door.
I had some serious issues with air leaks and solved them by getting a drop cord trouble light and going around under the dash and floorboard area and observing, when the hood is open and underneath where the light shines through. This takes two people. you will be surprised. mark the areas and get expanding foam and seal it., then spray it black
If you have a drivers door you may have to redo the rubber seal or double it up.
Your dash air and heater will not heat or cool your whole coach but should keep you comfy up front if you keep out cold air intrusion if its functioning properly.

Are you sure the AC wasn't on instead of heat?? We have no problem staying comfortable at 40 temps.

My monico was great when parked, but rolling down the road in the winter, those two massive pieces of glass making up the front windshield raidated cold air. The dash heat worked well to keep my toes warm and that area comfortable down to about 40F, below that if I do not have the furnace set to 65-68 I cannot stay warm either.

Heat? Still running the A/C in Fla.