SECTION 9: T
ROUBLESHOOTING
37
Pressure switch does not
Check flue/air supply duct for obstructions; remove any obstructions.
operate.
Check for loose/leaky air hoses to the pressure switch; repair/
replace/tighten hoses as required. Check for 24V across the secondary
terminals 4 and 5 (red and yellow wires) of the transformer.
IF NO: Check for 120V across the primary terminals 1 and 3 (black and
white wires) of the transformer. If 120V is present, replace
transformer. If 120V is not present, check wiring between power
cord, blower motor and transformer.
IF YES:Connect a jumper wire across pressure switch terminals; if jumper
wire allows blower to operate, replace pressure switch
(
See Page 45, Section 12.1.1
for part number that applies to your
unit rating). Do not resume normal heater operation until
replacement pressure switch has been installed.
Igniter spark gap incorrect.
Reset spark gap to 1/8" (3.175 mm).
BURNER DOES NOT LIGHT
Possible Cause
Try this....
Air in the gas line.
Purge gas lines.
Improper gas inlet pressure.
Check gas inlet pressure at the supply line. Gas inlet pressure should be
as follows:
Natural Gas:
5.0" w.c. (12.4 mbar) minimum;
14.0" w.c. (34.8 mbar) maximum
LP Gas:
11.0" w.c. (27.4 mbar) minimum;
14.0" w.c. (34.8 mbar) maximum
If gas inlet pressure does not meet inlet pressure requirements, contact
the gas company.
Gas valve does not open.
Check for 24V across valve terminals.
IF NO: Check wiring between the ignition module and the valve. Repair/
replace wires as required. If wiring is OK, replace ignition module.
IF YES: Replace gas valve.
Low gas outlet pressure.
Check gas manifold pressure. Measure manifold pressure at the pressure
tap on the gas valve.
See Page 35, Figure 33
and Page 38, Figure 34
.
Natural Gas:
3.5" w.c. (8.7 mbar)
LP Gas:
10.5" w.c. (26.1 mbar)
If manifold pressure does not meet requirements, adjust valve outlet
pressure with the adjustment screw on the valve.
NOTE:
Proper inlet gas pressure must be verified before performing outlet
pressure testing.
