Furnace Issues

[T Lejko]

Looking for suggestions on next steps. Our 2021 Gulf Stream cruiser furnace seems to have some issues. The blower comes on and shortly afterwards it ignites and hot air is produced. The issue is how long the hot air blows. The furnace ignites but only blows hot air for anywhere from 2 minutes to 10 seconds before the hot air stops. The fan keeps blowing and eventually it ignites. We are on shore power and the propane tank is fairly full. Thoughts?

[Leisure Time Larry]

First do some simple checks to rule them out. Confirm it's not a propane problem. Newbies often don't know about the protection valves in propane tanks and cylinders that restrict flow if it "thinks" there is a large leak. They can be activated simply by turning the valve on too fast. The valve should be turned on practically as slow as possible for the first half turn or so, until it is noticeable that gas has been released and it's charging the lines, then it can be opened the rest of the way at any speed. Check flow by lighting a range burner on high. If the flame is big and bright, you should be good, otherwise close the main propane valves and reopen them as above.

Next, turn your thermostat up higher, like 10 or more degrees higher than the air temp to see if it is acting weird. Make sure a heater register is not blowing at the thermostat making it think it's hotter than it is inside.

Make sure there are no blockages of the heater intake on the inside, exhaust on the outside, or any of the register outlets. Basically, anything that could cause an overheat safety to trip.

If all good here, it's time to dig deeper. Get your model and serial numbers of the furnace. Download the manual, and follow any troubleshooting steps in there. Use YouTube and Google to assist you if you are the DIY type. Hire a mobile RV mechanic or take it to a shop if you're not.

It seems like a couple of furnace issues are the sail switch and the flame sensor. The sail switch is a switch that acts like a sail, if you can believe it! It is a safety thing that makes sure there is adequate air flow for combustion. If not, no burner. A piece inside acts like a sail. Flow from the fan catches the sail and it connects the switch contacts, saying, "We're good for flame!" If pet hair, human hair or any other debris gets in there, it can block the switch from working properly. Sometimes, cleaning it works. Sometimes, switches go bad.

The flame sensor is just that, it senses when the burner is on and there is a flame. If it malfunctions, there can be issues like you describe.

Be safe, and good luck.

[THenne1713]

Remove, clean and reinstall the IGNITER and push on electric connector. It also acts as Thermocouple/ Flame Detector, and sounds like it is putting out sketchy voltage? Flame should be solid blue, well defined shape, and hitting igniter. If not, pull AIR-MIXTURE TUBE and clean of any insect debris. Good Luck.