Sf30 furnace

[Trucker2565]

2016 hideout furnace stops working at altitude. Sometimes works sometimes wont cycle. Changed to dinosaur board after 2 failed boards. Changed sail switch changed thermostat to digital. Works great under 6500 ft. Get above that and it may or may not work. If I tap the case it generally comes back on. Dinosaur says it sail switch but already replaced it . Any ideas????

[Keystoned]

Check the limit switch for good contact by removing and replacing both leads...wiggle them off and on to clean the contacts.

[flybouy]

Did it ever work at high altitude? When it doesn't work does it go thru the motions to start (i.e. does the fan come on, the ignitor fire?) If your LP tanks are near empty it may not have enough pressure at altitude.

[Trucker2565]

Sometimes it comes on just fine. Blower 1st then ignition. Other times blower then no ignition like it's not sensing airflow to ignite. It's a pain to get to but when I get to furnace if I tap/ smack the furnace box it will ignite.. i figure that out in a snowstorm above 9000 ft. I was looking for loose wires and I accidentally dropped my screwdriver on casing and it cam on so that's how I operated it most of the weekend. Last weekend about 8500 ft. I turned it on before bed. It came right on. At 1130 I got up and it had cycled and was on normally. Then 5 am gor up freezing it hadn't kicked back on again. Went outside and tapped box hard and it started blowing heat.

[Keystoned]

Sounds like a loose connection somewhere...

[sourdough]

I've never had a problem with my furnace at elevation but the number of nights spent at 8500+ are few. I have stayed in the 6-7k elevation quite a bit.

This may be completely off base and I've not heard of it in an RV but....

Our house in the mountains was at 9000'. Bought a new propane fireplace to go in the den. It did exactly what yours is doing. I tried replacing various piece parts to no avail. Finally called the propane company to have everything about the propane checked. All was good but he told me the fireplace was not designed to work at that altitude. The oxygen sensor was causing it to fail....there were no alternative sensors for it. He said they had tried selling that brand at their store but they wouldn't work up there. Had to give it away "down the mountain". Maybe a similar issue?

[flybouy]

My SIL lives around Divide, CO at a 10,800' elevation. All the houses in the development are all electric. She and her husband bought a LP grill. It would take about 45 min to cook a hot dog. They took it back and bought an electric grill.

[Trucker2565]

Well suburban says their furnaces are only rated to 4500 ft. Without adjustment ts but since I'm not a (certified repair facility ) she wouldnt tell me what I can do. I thinks that's crazy to build an rv furnace that is rated for 4500 ft. Havent they heard about mountains?? If I put a little dielectric grease on connections..... would that hurt anything??

[chuckster57]

Things get HOT, I don’t know that I would put anything on connections in the furnace.