19- Removescrewsalongvestibulesidesandbottom
whichsecurevestibulepanelandheatexchangeras-
semblytocabinet.Removetwoscrewsfromblower
railwhichsecurebottomheatexchangerflange,Re-
moveheatexchangerfromfurnacecabinet,
20- Backwashheatexchangerwithsoapywatersolution
orsteam,If steamis usedit mustbebelow275°F
(135°C).
21 - Thoroughly rinse and drain the heat exchanger. Soap
solutions can be corrosive, Take care to rinse entire
assembly.
22 - Reinstall heat exchanger into cabinet making sure that
the clamshells of the heat exchanger assembly are
resting on the support located at the rear of the cabi-
net. Remove the indoor blower to view this area
through the blower opening,
23 - Re-secure the supporting screws along the vestibule
sides and bottom to the cabinet,
24-Reinstall cabinet screws on front flange at blower
deck.
25 - Reinstall the primary limit on the vestibule panel.
26 - Route heating component wiring through hole in blow-
er deck and reinsert strain relief bushing,
27 - Reinstall electrical junction box.
28 - Reinstall the combustion air inducer. Reconnect the
4-pin plug to the wire harness. Reconnect the two
wires to the backup secondary limit, if applicable,
29 - Reinstall pressure switches and reconnect pressure
switch wiring.
30 - Carefully connect combustion air pressure switch hos-
ing from pressure switches to proper stubs on cold end
header collector box,
31 - Reinstall condensate collars on each side of the fur-
nace. Reconnect drain tubing to collector box,
32 - Reinstall condensate trap on same side as exhaust
pipe. Reconnect condensate drain line to the conden-
sate trap.
33 - Use securing screws to reinstall flue collars to either
side of the furnace. Reconnect exhaust piping and ex-
haust drain tubing,
34 - Replace flexible exhaust tee on combustion air induc-
er and flue collars, Secure using three existing hose
clamps,
35 - Reinstall burner box assembly in vestibule area,
36 - Reconnect flame roll-out switch wires.
37 - Reconnect sensor wire and reconnect 2-pin plug from
ignitor,
38 - Secure burner box assembly to vestibule panel using
four existing screws. Make sure burners line up in
center of burner ports.
39- Reinstall gas valve manifold assembly, Reconnect
gas supply line to gas valve,
40 - Reinstall burner box cover,
41 - Reconnect 2-pin plug to gas valve,
42 - Replace the blower compartment access panel.
43 - Refer to instruction on verifying gas and electrical con-
nections when re-establishing supplies.
44 - Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
45 - Replace heating compartment access panel,
Cleaning the Burner Assembly
1 - Turn off electrical and gas power supplies to furnace,
Remove upper and lower furnace access panels,
2 - Disconnect the 2-pin plug from the gas valve,
3 - Disconnect the gas supply line from the gas valve, Re-
move gas valve/manifold assembly.
4 - Mark and disconnect sensor wire from the sensor. Dis-
connect 2-pin plug from the ignitor at the burner box.
5 - Remove burner box cover and remove four screws
which secure burner box assembly to vest panel, Re-
move burner box from the unit.
NOTE - G71MPP-135 units are secured to the vesti-
bule panel by two additional screws. These screws
must be removed for servicing, however it is not nec-
essary to replace the screws.
6 - Use the soft brush attachment on a vacuum cleaner to
gently clean the face of the burners, Visually inspect
the inside of the burners and crossovers for any block-
age caused by foreign matter, Remove any blockage.
7 - Reconnect the sensor wire and reconnect the 2-pin
plug to the ignitor wiring harness.
8 - Reinstall the burner box assembly using the existing
four screws. Make sure that the burners line up in the
center of the burner ports.
9 - Reinstall the gas valve manifold assembly, Reconnect
the gas supply line to the gas valve, Reinstall the burn-
er box cover.
10 - Reconnect 2-pin plug to gas valve,
11 - Replace the blower compartment access panel.
12 - Refer to instruction on verifying gas and electrical con-
nections when re-establishing supplies.
13- Follow lighting instructions to light and operate fur-
nace for 5 minutes to ensure that heat exchanger is
clean and dry and that furnace is operating properly.
14 - Replace heating compartment access panel,
Page 58
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