MAIN POWER "J" BOX
The main power "J"-box is on the left
side of the furnace blower
compartment and must have line
power connected with proper
polarity. The "J" box can be moved to
the opposite side on upflow units to
facilitate installation in the field.
Failure to connect line power with
proper polarity may cause the
system not to sense flame and shut
down. After several trials for ignition,
the system goes into lockout.
A grounding wire is provided to
connect to the incoming grounding
wire from line power. The furnace
must be permanently grounded in
accordance with all national and
local codes.
BLOWER DOOR SWITCH
A blower door switch is attached to
the "J" box. The switch closes by
putting the blower door in place. The
door must be properly installed to
ensure that the switch closes its
contacts. It is designed to break all
power to the furnace if the blower
door opens. The switch is in the 115
volt primary circuit.
Check. The following voltage test
can be used.
1. With power on to the furnace,
remove the blower door.
2. Remove the Molex connector
carrying 120 vac at the IFC.
3. Press and hold in the blower
door switch.
4. Use a voltmeter to check for 120
vac between the black and white
wires at the connector.
5.
A 120 vac reading indicates a
good blower door switch.
6. If there is a zero (0) vac reading,
replace the switch.
The condition of the blower door
switch can be verified with an
ohmmeter. If the meter shows
continuity the switch is good. If the
meter shows an open circuit, replace
the switch.
FIGURE 87
MAIN POWER "J" BOX
FIGURESS
BLOWER DOOR SWITCH
75
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