"Ed Sievers" wrote in message
...
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.




From all that you've done I would suspect your igniter. You should be able
to see it glow if it's OK--no fire since you indicate that your gas valve
didn't open. As noted in another post, get it fixed and chalk it up to the
lightning strike--your insurance should cover the cost. On your bill have
it noted that failure was due to lighting.
MLD