Troubleshooting
SYMPTOM
POSSIBLE CAUSE
CORRECTIVE ACTION
1. Furnace operates,
but turns "OFF"
before room
temperature is
attained.
A. External thermostat location.
Check the thermostat location. It should not be
in the path of warm air discharge from the
furnace, near a lamp or above a T.V. or stereo
set.
B. Defective external thermostat.
Check the thermostat calibration or replace.
2. Furnace not
producing sufficient
heat.
A. Furnace may be too small for space
being heated.
Check heat calculations.
B. Furnace not burning at full rate.
Check for low gas pressure. Check the burner
orifice.
3. Furnace operates,
but will not shut
"OFF" when room
temperature is
attained.
A. External thermostat wiring defective.
Thermostat lead wires may be shorted
together, by a nail or staple. Check by
removing thermostat leads from the valve
terminals.
B. External thermostat location.
Check the thermostat location. If on an outside
wall or there is a hole in the wall behind the
thermostat causing cold air to contact the
thermostat. Relocate the thermostat.
C. Defective external thermostat.
Check the thermostat calibration or replace.
D. Defective valve.
Replace the valve.
4. Abnormal
operation.
A. Expansion noise ticking.
Casing may be distorted by being fastened to
an uneven wall. Vent tube and air inlet tube
may be in a bind with a vent cap assembly. Be
sure the hole through the wall is correct and
parts fit without binding.
5. Noisy Blower.
A. Housing rattling.
Tighten blower housing screws.
B. Blower dirty.
Clean blower wheel.
C. Blower wheel bent.
Straighten or replace.
6. A1 Error Code.
Flame loss or flame not present lockout.
Check gas supply. Check flame sensor
connection;
check
hot
surface
igniter
connection. Replace sensor or hot surface
igniter if necessary.
7. A2 Error Code.
Condensing water High level reached.
Check condensate trap hoses for blockage.
8. A5 Error Code.
Hi Limit Lockout.
Check circulation fan motor connections and
replace motor if necessary; check hi limit
switch connections and replace switch if
necessary; check inducer fan hi limit switch
connections.
9. A7 Error Code.
Air flow not sufficient.
Check air pressure sensor wiring connections;
check air pressure sensor hose connections
and replace sensor if necessary; check for
blocked exhaust.
10. A8 Error Code.
Room probe too high.
Check thermistor asy. Connections and
replace if necessary.
11. A9 Error Code.
Room probe failure.
Check thermistor asy. Connections and
replace if necessary.
12. Gas valve is not
modulating.
Faulty wiring or JP5 jumper on control
board.
Check harness connections and replace if
faulty; JP5 jumper should not be present on
NG model; JP5 jumper should be present on
LP model.
