Suburban Furnace High Elevation Problems

Could be oil trap in copper line to furnace blocking gas flow when colder (higher viscosity) at altitude. Just a possibility.

Had same problem again camping at 9,100 ft. But I was able to fix the problem finally. Bottom line: increased the gap on the ignitor and she fired right up.

Hope this helps anyone else who has similar problem. Note, before I increased the gap, when the unit was not lighting, I could view into the combustion chamber and observe a spark, this was adequate for lighting at 5,200 ft but not at higher elevations until the gap was increased.

Try turning the LP regulator down a bit. Back out the adjustment about three full turns and try furnace. Might work, has for me a couple of times with the water heater. Don't forget to reset the same amount when you get home.
Art.

No ideas or suggestions. And not sure what "older" is, but our 2007 Surburban furnace works fine at about 8,500' on our annual trip to Colorado.