amarzano Report post Posted January 15, 2011 Last night our furnace stopped heating. The fan runs - but the furnace does NOT kick in.We do have a full tank of LPG and are on shore power. It was working earlier in the evening - then the DW started pushing buttons on the thermostat and it stopped...We ran the heat pump last night which might be a better option - since we don't use LPG.. Heat pump is controlled by same thermostat as furnace.Any thoughts or suggestions on what to check and where it would be located?This is a Suburban furnace mount under the fridge. Stove, fridge and water heater all are functioning normal. We have a 2011 Berkshire 390bh by Forest River.It was dark and cold when this happened last night - so I didn't wander outside - but will start looking for tripped breakers today.Thank youAlex Share this post Link to post Share on other sites
tbutler Report post Posted January 16, 2011 It sounds like button pressing might be the problem. I would get out the manual and check the settings. If we're talking about the Dometic Duo-Therm thermostat, check the mode-- should be on furnace. Check to see that the fan is on auto. After that, go outside and have DW turn up the thermostat. Listen to see if the ignition is sparking. If no spark it could be a loose connection or it could be a computer board problem. If it sparks but you get no ignition, clean the burner tube to make sure there are no obstructions (even spider webs can cause it to fail to ignite). If all else fails, it could be a reed switch in the fan housing which detects the fan operation. If the switch fails to close the computer will not know the fan is working and will not start the furnace. We had ours replaced several years ago, took several days for the repair center to get a replacement switch. Let us know more about your system and what you have found so far. Perhaps others can suggest other things to check. Share this post Link to post Share on other sites
dalltop Report post Posted January 16, 2011 The other LP appliances are working so I would look at the furnace. The LP pressure can be a factor especially when the tank is low and it is very cold outside. When the thermostat calls for heat, power is sent to the furnace. The blower starts, current passes through a sensor to check to be sure the furnace heat exchanger is not too hot. If the temprature is ok and the sail switch is closed then the circuit is complete to the control board. Sail switch verifies the blower fan is spinning fast enough. After both these conditions have been met, the control board will open the gas valve and send a spark to the ignitor. If the furnace fires and burns, the same ignitor is used by the control board to measure voltage passing through the burning gas to ground. The control board will keep the gas valve open as long as the voltage indicates that the flame is still burning and the thermostat is calling for heat. In most cases the furnace will try 3 times to start and if any of the above conditions are not met, it will lock out until you turn off the furnace. Turn the furnace off and wait for the cool down timer to shut the furnace off. Turn it back on an see if it will reset. You really should have the unit inspected if it keeps failing to start. It is not that hard to work on but you will need to know how to test and check for leaks. It can be a pain to remove from the coach. Share this post Link to post Share on other sites
amarzano Report post Posted January 16, 2011 Thank you for the great tips. In the light of day, I checked the fuse box. The 15 amp fuse for the furnace was blown. The furnace is working again. A bit off topic, but if you have shore power is it better to heat with the furnace or the heat pumps? Both seem to get the job done, but I am wondering if one would be more efficient. Of course we pay for propane and not shore power.. Thank you Alex Share this post Link to post Share on other sites
shields Report post Posted January 19, 2011 We seem to get faster results with the furnace; so we use it even though the shore power (for heat pumps) is free. Glad your problem was simple to resolve. Tim Share this post Link to post Share on other sites
garykd Report post Posted January 21, 2011 Hi Alex, If you have a 5 button T'Stat, Duo Therm Heap Pumps, Suburban furnace and the coach manufacturer set the dip switches on the front heat pump correctly, this decision gets real easy. Set the T'stat for the heat pumps (front and rear). The heat pumps will do a good job and use CG electric, not your propane. When the outside temp gets into the low 40's you may hear the heat pump running, but no fan. This is a defrost cycle and will last about 5 minutes. Do not worry this is normal and allow the heat pump to operate down to the low 30's. When the outside temp gets to the low 30's the 5 button Comfort Control T'stat will automatically switch to the furnace. Once the outside reaches the high 30's (around 38 degrees) it will automatically switch back to heat pump. All the above is done without you doing anything. Look in your Comfort Control Operating Instructions. This feature is toward the back, in or around page 7. The above is how my coach is wired. It works as advertised and it is a nice feature. Share this post Link to post Share on other sites
Goldwing2 Report post Posted February 4, 2015 See RV Comfort Control.ZC Share this post Link to post Share on other sites
