Gary Stone wrote:

Hi, I've got a forced air propane furnace, Luxaire model GSU082MF Series
NAGOE (could be a Q) serial #1310002
Controlled by a Honeywell T87F heat only thermostat. This morning I was down
in the basement and noticed that it had the initial ignition then that cut
off after a while (normal burn) then a couple of minutes later a second
ignition which ran a couple of minutes, when that cut off I headed up the
stairs only to hear it kick in a third time for a couple of minutes. Total
time for this was about 10 to 13 minutes. Before I went down there I had
moved the thermostat only to the point which it kicked in, 60º F from 58º F
so, it wasn't that drastic a jump. Yeah, I like it on the cool side. The
outside temp was 19º F. I do not remember it ever acting in this manner and
suspect there might be a problem, Yes? No? Thanks for any input.

My guess is the "stack cutoff" sensor is bad. The idea is that shortly
after the ignition goes on, the gas should lite and heat up the stack.
If it doesn't, the ignition will be killed. But after several tries,
it gets warm enough to stay on. Maybe the cold outside temp has
something to do with it.

The sensor probably needs to be replaced. It's a safety-related item
and the repair should be done by a licensed professional.