Carrier 48GH - Manual (Page 21)

SYMPTOM
Pilot Will Not Light
Burners Will Not Ignite
Inadequate Heating
TROUBLESHOOTING CHARTS
Table 7 — Heating Service Analysis Chart
Poor Flame Characteristics
_______ _ CAUSE
No spark at electrode
Spark shorting out to main
burner _____
No gas at pilot burner
Water in gas line_____
No power to furnace
REMEDY
Check air gap between electrode tip and pilot
burner Gap should be as shown in Fig 10
Readjust as necessary
Clean moisture or dirt accumulation on electrode
ceramic with cloth.
Cracked ceramic — replace pilot electrode
assembly.
Check for loose or broken wiring at and between
spark generator and electrode. Replace wire or
tighten connection as necessary.
Check fuses or circuit breaker to ensure voltage
to utiit___ _______ _ ______________________
Check 24-volt input to spark generator If you read
24 volts and above steps have been completed,
replace spark generator_____ _________
Realign electrode tip away from main burner but
maintain spark gap to pilot burner. See Fig i 0._
Clean pilot orifice
No 24-volt power supply to
contro!_ circuit___ ________
IVhswired or loose connections
Dirty pilot — yellow flame^
Pilot burning properly —
sharp blue flame____
Burned out heat anticipator
in thermostat
No gas at main burners
Broken thermostat wire
Dirty air filter
Gas input to furnace too low
Unit undersizeçLfor application
Restricted airflow
Blower speed too low __
Limit switch cycles main burners
Incomplete combustion results in
Aldehyde odors, (CO), sooting
flame — floating flame
Check for voltage to terminals 3 and 5 of
gas valve
_________ __
Check to see if pilot valve is opening Check for
loose or broken wiring connections If no
deficiency is found, replace gas valve
Drain
install water trap.___
Check power supply, fuses, wiring,
breaker. or circuit
Check transformer — replace if necessary
Checl^all wiring^ and wirenut connections.
Clean pilot orifice.
______________
Replace pilot
Replace thermostat.
Check to see if main gas valve is opening Look
for loose or broken wiring connections. If no
deficiency is found, replace valve assembly.
Run continuity check to locate break.
Replace filter.
Check gas pressure at manifold. Clock gas meter
for input. If too low, increase manifold pressure
or replace with correct orifices.
___
Replace with proper uriit^—or add additional unit.
Clean or replace filter — or remove any
restriction.__________ _________ _____
Use faster speed tap — or install optional blower
Dirty air filters — clean or replace.
Registers closed, restricted ductwork
remove restriction.
open or
Check heat anticipator setting on thermostat —
readjust._______________
Air shutters on burners closed — adjust to
soft blue flame.
Check all screws around flue outlets and burner
compartment — tighten
_______________ _
Lack of combustion air.
Cracked heat exchanger — replace.
Overfired furnace — reduce input or change
orifices.
Check vent for restriction — clean as required
Check orifice to burner alignment
21