I have a 2 year old Trane XR 80 gas furnace that's been trouble free up
until I noticed something this morning.
When I call for heat. The combustion blower ( not the main blower)
comes on as ir should, but after 3 seconds it shuts off, then comes on
about 4 seconds later and then shuts off. It repeats this cycle
indefinately.
So I figured it is one of 2 things. A bad T-stat or some limit switch
is bad. When I opened the panel, I noticed a cylindrical limit switch
with a clear tube on it which leads into where the combustion chamber
is. My guess is that it senses if the combustion blower is on. So I
removed the clear tube and blew in it to clear any particles out of it.
I then jumped the T-stat terminals at the furnace and the furnace came
on with no problems.
When I put everything back together, the furnace operated normally. So
now I don't know what caused the problem.
What usually causes this problem? And also does anyone know what the
limit switch with the clear tube on it is for?