On 10/05/10 03:06 pm, Bob Villa wrote:

I do already have a service call scheduled for Thursday morning, but I
wouldn't mind having a rough idea how much the problem might cost to fix.

It's an 8-yr-old Lennox G32 that we turned on (that is, we switched the
thermostat from Cool to Heat) a couple of days ago. We hear the blower
start up, but it stops a few minutes later without the set temperature
having been reached.

The LED indicators show that the burner has not ignited, and there is a
strange noise when the blower is running -- not exactly a rattle, but it
sounds as though something may be rubbing/scraping against something else.

I know that the HVAC company we've called advertises furnace inspections
for $69, but I don't know how much time that covers, and obviously it
wouldn't cover any needed parts.

Any intelligent estimates?

Unlike A/C the furnace has to have a clear exhaust and a vacuum switch
prevents ignition. I'm betting you have a clogged PVC vent (leaves or
rodent nest).
The blower is the same...so maybe the crap is scraping the exhaust gas
fan.

See my response to Ken: water, not leaves or rodent nest.

Perce