Hi all, hopefully you can provide some help to me on this...
I have a Clare NG 70,000 BTU furnace that is about 13 years old.
model #: HEMI 70 8D
Code #: 2308M39
Serial #: H0158535
hot surface ignition
new (2 days old) programmable digital thermostat that replaced what a tech said was a defective one.
the problem started a week ago when after several weeks of the furnace working fine (worked fine last winter too), it was blowing continuously cold air. I checked it out and sure enough ... no flames.
I was able to take it apart somewhat and sand off the flame sensor and I found that the hot surface igniter was cracked in pieces. I got a hold of a local tech and he replaced the HSI. Still no flames - so he checked out the thermostat and bypassed it - connecting red and white wires and everything seemed to work.
So i replaced the thermostat. The furnace then worked for approx 1 day - off and on when it should, maintaining the temp in the house as programmed.
Now this morning, i wake up to cold air blowing out of the ducts and the furnace mainboard is flashing a single flash indicating lockout. Turning off the power to the furnace for 1 min allowed the HSI to light, but again... no flames and the LED is blinking lockout again.
Flame sensor need replacing? Or high/limit switch? Any help would be appreciated.