The RV furnace has always worked well, but this last week it seems it isn’t heating the interior as quickly as it did a few months ago. I checked the vents and nothing is blocking them. The air blowing is warm but used to be much warmer. And while the heat is on, I can’t light the stove burners; I have to turn the furnace off, and then the stove will light. That has never happened before, so I think the two may be related. —Cheryl, 2016 Coachmen Leprechaun 220QB
You might have a couple of issues going on here. I would start by verifying there is 12-volt power to the RV furnace. I know I sound like a scratched record; however, low voltage is the culprit the majority of times in these situations. First, does this happen when you are connected to shoreline power or dry camping? If you are connected to shoreline power, the converter should be putting at least 13.2 volts into the furnace and 13.6 volts if the batteries are no good.
Get a multimeter and verify what voltage you have at the batteries.
The next thing I would do is verify what voltage is at the module board at the furnace. Doing this means taking some of the housing apart from the backside. It may not be something you are comfortable with.
If you are getting low voltage, then there is something wrong with your wiring. I would then take the unit out and bench-test it with a good 12-volt source and open venting. This would verify that the motor is running fast enough to lift the sail switch and that there is good airflow coming from the return air intake and going out over the burner assembly. It would also verify good airflow coming from the outside air intake and going out the other air exchange, and that the unit is lighting and the burner assembly is good. You can take a look at the outside vents to make sure they are not clogged. Then look inside and make sure none of the supply hoses is kinked or disconnected.
I have seen situations where the main supply hose coming off the RV furnace has slipped off and warm air is blown into the basement and not to the vents. This could be one reason you are getting lower airflow and temps.
Could be a weak regulator
Another issue could be a weak regulator, especially since you need to shut the furnace down to light the stovetop burner. Since you have a Class C, your unit has an ASME tank with a regulator on the tank. Typically, a technician would check the regulator using a water column tester at the furnace or other appliance. It should read 11” of water column. You can do a manual test by turning on one of the burners at the stovetop and then slowly turning on another. Watch to see how the flame reacts—it should be a steady blue. If it is jumping around, orange, or goes down and does not come back up, then the regulator is not getting enough pressure through it. I would recommend getting a technician to test it professionally and change it, as well.
You might also enjoy this from Dave
RV ‘Gremlins’, Part 5: Forced air furnaces and why they’re so finicky
I typically don’t get as many questions about furnace efficiency as other appliances, mostly because of how people are using their units and how often the furnace actually gets used.
Most RVers store their rigs in the winter, so the furnace only gets used slightly when the temperature dips in the mountains or during autumn, so it doesn’t get tested as much in extreme conditions.
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
Read more from Dave here.
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