PMP
Oil Furnaces
–
Furnace Manual
670-000-003/1010
19
9
Troubleshooting
Check 120 volt supply to furnace. If there is no supply
To successfully service the oil furnace, you must
voltage, check fuses and service switch. CAUTION :
have these instruments :
When testing electrical equipment, always follow
smoke tester
standard electrical safety procedures.
carbon-dioxide (CO
2
) or oxygen (O
2
) analyzer
draft gauge (scale should read from -.01” w.c. to -.25” w.c.)
volt/OHM/milliamper multimeter
pressure gauge capable of reading 0-150 lb/sq. inch (for oil only)
Be familiar with these instruments as well as the burner
manufacturers recommended settings.
Before beginning these troubleshooting procedures, ALWAYS :
Make sure thermostat is calling for burner operation.
Check oil supply and make sure all valves are open.
Sym ptom – Burner
Check fuses and make sure service switch
is o n.
Check for vol tag e from primary re lay to
bu rner motor. Make sure th e prima ry relay
ha s not locke d o ut on safety.
Check for li ne volta ge into furnace jun ction
box.
Make sure the thermostat is calling for heat and
that the wiring to the thermostat is correct and t ight.
If the prima ry relay control is not po pping
out
th e
reset
b utton,
measure
the
milliamp erage at th e thermostat and se t the
heat-an ticipator
a ccord ingly.
A lso
check
wiring fr om the thermostat to the bu rner.
Check the alig nment of th e cad cell to
assure it is aimed at the fire.
Ch eck nozzle a nd electr ode position.
Check ig nition tra nsforme r ou tpu t
(Reference burner man ufa cturers
instructio ns) .
Check tube insertion and ali gnment.
Check n ozzle and electrode position
(Reference burn er ma nufacture rs
instructions).
Replace nozzl e.
Check
pump
pressure
(va ries
with
manu facturer and ap plicati on; se e burne r
manu al).
Check overfire draft.
1. Remove CA D cell leadwires from the f-f
terminals on the p rimary safety con tro l, then
sta rt burner. S hortly after burner starts,
place
a
temporar y
jumpe r
b etween
terminals f-f. Co nnect oh mete r a cro ss CA D
cell lead wires-re sistance should b e under
1,600 ohms.
3. Wi th burner off, check dark cel l resista nce
across
CA D
cell
leadwires.
Resista nce
shoul d b e gr eater than 20 ,00 0 o hms. If cel l
resistances
a re
differe nt
from
above,
reche ck wi ring and lo ca tion of cell , etc. If
ne cessary, rep lace p lug-in portion of ce ll.
2. Stop burne r a nd remove tempor ary jumpe r.
Possible correct ions :
To check CAD cell operation, use t he
following proce dure :
Burner m otor does not sta rt.
Unable to a chieve clean combustion
by se tting air adjustme nts .
Burner s hort c ycles or locks out on
prim ary re lay safety.
Symptom – Furnace blower
Check for 120V to the blower motor. If
present, replace motor.
Check wiring from Fan and Limit control. See
if blower motor will run when it is switched on
manually at the thermostat sub-base (if sub-
base is installed).
Blower short cycles on limit control.
Return ducts may be undersized.
Possible corrections :
Furnace blower will not start.
