31W Heater question

[RMS31W]

I'm not getting any measurable flow from the bathroom heat vent as well as the vent by the fridge. I get lots of flow from the vent in the bedroom and the vent under the both dinette, both of these are on the furnace side.
I took it in yesterday to have it fixed and they said the flow was restricted and they corrected it, so this morning I tested it and no flow. In fact I can't tell any difference. Anyone else having same problem?

[blw2]

I honestly never noticed in my 31L one way or the other.....
I turn on the furnace and the coach warms up good enough. Thinking about it, I probably would have subconsciously dismissed cold areas as normal for a "camper"
.... but as I keep reminding myself, this 'aint camping!

[Beacher]

RV furnace ducting is very basic, even on the most expensive class-A DPs.

It's rarely ever balanced as a home system would be with different sized ducts, air valves, and vents so that the air flow is very similar from all vents. In an RV it's simply about distribution, (just getting the air there).

Unless there is some physical object blocking the air flow, the flow restriction results from the bends and duct length to the farthest vents. The closer vents, (to the blower fan), blow more air than the farthest vents.

If you really want to balance the air flow throughout the system, (it's very easy), you restrict the vents closest to the fan blower motor, (with some foil tape behind the vent grills). That will increase the air flow to the farthest duct vents.

If that doesn't work, then there is something physically blocking the air in the ducting. It's likely that the air is being blocked by a rat, family of mice, a bat, squirrel, snake, bunny rabbit, or something completely boring like leftover assembly/manufacturing material.

And, you don't want to haphazardly stick anything damaging in the ducts to randomly probe for blockage as the RV HVAC duct hoses are typically manufactured from ridiculous fine delicate metal/plastic gossamer that makes gold -leaf seem sturdy. In the walls/floors/ceilings you will find some sort of soft high-tech insulating foam, (usually Styrofoam) channels at acute and right angles. So, if you do need to probe, do so very gently with something very soft and flexible.

[FW28z]

The flexible ducting they typically use has a lot of air flow restriction, especially if you have a bend or two.

The forward-most duct in my rig is only about 2" in diameter and goes through at least 2 90Deg bends and is probably 20ft long. I get hardly any air flow through it.

[RMS31W]

Yeah air is like water, always follows path of least resistance. My two strong vents are in line with the blower, one on each side of the blower with each vent being about 8 feet from the blower. The two that don't work are on the other side again about 8 feet from the blower. I guess the 90 degree joint to send the across the coach is causing the problem. I guess I'll try restricting the stronger vents and see if that boosts the weak ones. Would be curious if anyone with a 31W has the same issue.