Electrical Controls And Wiring - Carrier 58MXA Instruction Manual

1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Disconnect igniter wire connection.
4. Check igniter resistance.
a. Using an ohm meter, check resistance across both igniter
leads in connector.
b. Cold reading should be between 45 ohms and 90 ohms.
c. If ohm reading is higher than 110 ohms, igniter is cracked
and must be replaced.
5. Remove igniter assembly.
Allow igniter to cool before removal. Normal operating
temperatures exceed 2000°F.
a. Do not remove igniter from bracket while assembly is in
furnace. Using a 1/4 in. nutdriver, remove screw securing
bracket and igniter assembly to bottom of burner box. The
screw in the bracket is always located toward outside of
burner box. The screw may be hidden by inlet box or inlet
pipe, but can be removed without removing either. After
removing screw, slide igniter and bracket toward outside of
burner box and pull straight out.
The igniter is fragile. DO NOT allow it to hit the side of the
burner box opening while removing or replacing it.
b. Inspect igniter for a white area indicating a crack may be
present. If found, replace igniter.
NOTE: A small crack cannot be seen on a new igniter. After a
period of operation, a white area will be visible around the crack.
c. If replacement is required, replace igniter on igniter bracket
external to furnace to avoid damage as the silicon portion is
very brittle and will easily crack or shatter.
d. To remove igniter from igniter bracket, remove screw
holding igniter ceramic block to bracket and pull ceramic
block out of bracket.
6. To replace igniter/igniter assembly, reverse items 5a through
5d.
7. Reconnect igniter wire connection.
8. Turn on gas and electrical supplies to furnace.
BURNER FLAME
MANIFOLD
Fig. 9—Burner Flame
9. Verify igniter operation by initiating furnace control board
10. Replace main furnace door.
Step 7—Electrical Controls and Wiring
There may be more than 1 electrical supply to the unit. Check
accessories and cooling unit for additional electrical supplies.
The electrical ground and polarity for 115-v wiring must be
maintained properly. Refer to Fig. 11 for field wiring information
and to Fig. 15 for unit wiring information.
NOTE: If the polarity is not correct, the STATUS LED on the
furnace control will flash rapidly and prevent the furnace from
operating. The control system also requires an earth ground for
proper operation of the furnace control and flame sensor.
The 24-v circuit contains an automotive-type, 3-amp fuse located
on the control center. (See Fig. 12.) Any direct shorts of the 24-v
wiring during installation, service, or maintenance will cause this
fuse to blow. If fuse replacement is required, use ONLY a fuse of
identical size (3-amp). The control LED will flash status code 24
when fuse needs to be replaced.
With power to the unit disconnected, check all electrical connec-
BURNER
tions for tightness. Tighten all screws on electrical connections. If
any smoky or burned connections are found, disassemble the
connection, clean all parts, strip wire, and reassemble properly and
securely.
Reconnect electrical supply to unit and observe unit through 1
complete operating cycle for proper operation.
A89020
8
PAM
RTV
Fig. 10—Gasket on Collector Box
self-test feature or by cycling thermostat.
A93081