On Oct 15, 9:44*pm, "Ed Sievers" wrote:
My daughter's furnace (and her little Boze radio) received a bit of a jolt
from a secondary leg of a lightning strike which hit (and penetrated) the
roof across the street this past summer. *I had to replace the furnace
control board ($132 wholesale from an AC parts house) and then the AC worked
just fine the rest of the summer. *I didn't c/o the heater at the time, but
she tried it the other day and it doesn't work. *I was very careful ground
myself while installing the replacement controller last summer so as to
avoid static discharge and of course labeled all the wiring to ensure I
connected it up right. *Now, on startup, the induced draft fan starts a
couple of times and on the 3rd try or so, gets up enuff speed to trip the
draft sensor switch and keep running. *The hot-surface ignitor never heats
up though nor does the gas valve open. *Without a normal startup, eventually
everything shuts down...as it should. *I thought maybe another lightning
strike near the house had "zapped" another controller, so I bought a
replacement + a spare. *I have tried both the new ones......same result..
All the flame roll-out sensors, hi-temp sensors, etc are "made" and the gas
valve reads about 150 ohms, so I believe it to be OK. *As a last resort, I
disconnected all the T'stat wiring (as per directions) and ran a "self
check" on the currently installed controller. *After an intitial delay, it
is supposed to turn on the draft blower and leave it on, then the ignitor
(for 15 seconds .... but not the gas valve) , then turn on the big blower at
low speed (heat) for abt 30 sec and then high speed (cool). *Instead, I just
get a flashing red status indicator light on the control board......and the
literature says this can either be: (1.) a problem with the 120 v. power
polarity (reversed) or (2.) a twining problem. *Well, the power is hooked
blk to blk and white to white (as it has been for 6 years now) so that isn't
the problem but what the heck is a "twining problem? *Also, since the first
event is supposed to be the induced draft fan coming on.......I'm wondering
if it may have some lightning-caused shorted turns or something. *I would
think that the control board only provides power to that little motor via *a
relay, but maybe the board gets feedback info and is "smart" enough to know
that the current draw to that little motor ain't right? *(That's a stretch,
but I am about at my wits end......and I intend to call out a tech who is
more up-to-date than I am on HVAC) *Any thoughts from any AC wizards out
there? *TIA.....ed s (long,long ago retired A/C dude) in TX.

Lightning strikes are covered by your insurance and the furnace and
radio should have been repaired/replaced free of charge. Most policies
are pretty liberal in that respect, so a call to your agent might be a
good idea even at this late date.
If you're stuck with doing your own repair, then look for the power
relay on the board that handles the ignition/fans or such and see if
it can be checked without desoldering. I had a Modine heater that quit
last winter and traced it to some cold solder joints on the relay.
Nice 10 minute fix made me proud.

Joe