RV Furnaces

Posted by admin on February 21, 2011

FURNACES
A major concern for RV’ers is a furnace quitting during the cold of winter. There are some basic checks before calling for service. Furnaces require a good 12-volt DC supply to operate. See the article BATTERY MAINTENANCE. If the furnace does not blow at all, check the fuse in the fuse panel. Many furnaces use a power switch and a circuit breaker located under the outside cover secured by two large screws or 4 small screws. Other models have these components located inside at the rear of the furnace, usually under a cover. If these checks pass inspection, most likely wiring connections, thermostat or the blower motor is defective. If it blows air and does not ignite properly, check that the LP gas system is operating
properly. Turn on a stove to verify good operation. If the stove operates poorly, it can be an indication of a low LP gas level, which in cold weather will provide poor performance. See the article PROPANE GAS BASICS. Airflow restrictions caused by the vents being blocked will also cause the unit not to operate properly. If the LP gas has run out, has recently been filled or the gas valve has been turned off, try to turn the thermostat off and back on through several cycles to possibly self-bleed the air lock out of the LP lines.
The Furnace’s theory of operation is as follows: The thermostat has a set of contacts that close when heat is required and open when the correct room temperature is obtained. When the thermostat contacts close they connect a set of wires together at the furnace, this activates a time delay control that activates the fan motor. The air movement from the fan activates a sail switch contacts that close, sending a signal to the DSI control board. After a short delay, the DSI control board opens the gas valves and sends a high voltage spark to the electrode located by the burner. The DSI module should sense a flame through the electrode. If a flame is not sensed, the furnace will lock out until the thermostat is reset. Older systems will continue to blow air and newer units will quit blowing until the thermostat is reset. When a furnace fails to start, some of the most common failures are: a blown fuse, tripped circuit breaker, defective wiring connections or a defective thermostat. If it will not ignite properly, the most common component failures are: a defective DSI module, blower motor, electrode or sail switch. DSI modules are known to cause intermittent operating problems that are often hard to diagnose. Humidity, heat and cold may cause an intermittent failure due to expansion and contraction.

We hope the information provided can help you locate and correct the problem. Safety should be of major concern when dealing with LP propane gas and carbon monoxide. If the furnace is not working properly after performing these basic tests, it is best to contact a qualified professional to properly diagnose and repair the furnace at (850) 866-6999 or visit http://www.rvtrax.com .

21Feb