By Dustin Simpson
When you bring your RV into our repair shop, or any repair shop, here’s an example of things we are testing during a bench test and some of the components we’re looking at for RV furnace issues: checking current, voltage, resistance, DC and AC power, circuit board, relay, blower motor, sail switch, high limit switch, gas valve, igniter, flame sensor.
Safety disclaimer: It’s important to note that your RV furnace operates using propane and electricity, two potentially dangerous sources.
If you are not confident in working with either, allow a professional technician to take care of the repairs.
How does an RV furnace work?
Here is the basic sequence of operations:
1. The thermostat sends an electrical signal to the furnace circuit board.
2. The signal passes through a relay and the blower motor starts.
3. At full speed, it activates the sail switch, confirming there is adequate airflow to exhaust fumes from the furnace.
4. The signal continues to the high-level switch, which indicates the temperature of the furnace is below a safe level to start.
5. With the two previous safety switches activated, the gas valve opens, allowing propane into the combustion chamber.
6. The igniter in the combustion chamber receives current from the ignition module on the circuit board. As a result, the current produces a spark between the ignitor tips. This lights the fuel and produces the flame, resulting in the heat flowing through the heating ducts throughout your RV.
RVer furnace issue problem
Complaint: Furnace not operating properly.
Cause: Was an intermittent condition from the PC board.
Cure: Along with servicing the unit, the PC board was replaced. This unit was actually installed twice and didn’t end up failing during the testing process.
Customers came in to pick up, and during testing with owners, the unit failed to operate during cycles.
Removed the unit for the second time and, after testing and monitoring, found the PC board was the issue.
If you’ve determined the circuit board is the cause of your furnace problem, it’s a relatively easy part to replace. The circuit board is usually located in the furnace’s blower chamber near the bottom of the unit.
The hard part is removing the furnace to access it for testing and bench testing.
Luckily, everything was repaired and reinstalled and then tested properly.
More from Dustin
Read more of Dustin’s articles here.
RELATED
- There’s a switch hiding in your furnace that could cost you $200 to push!
- An RV tech’s 7 tips to diagnose RV furnace vibration
- Keep your RV furnace running smoothly: Expert maintenance tips
RVDT2850
Yep. Circuit board was fast and easy to replace – However, it was several hours work to diagnose everything else was working properly and finally the big job, complete furnace removal to get at the circuit board and then reinstall and verify there were no propane leaks.
I learned another lesson, test your furnace in warmer weather before needing it in colder weather.