Service Manual

Does blower
energize?
N
Y
Sequence of operation:
With the thermostat calling for heat, prior to energizing blower, the ignition module checks the exhaust pressure switch for normal
s
witch position of normally open. If the exhaust pressure switch contacts are closed (not in normal position), the ignition module
waits 45 seconds for the pressure switch contacts to open. If the pressure switch contacts do not open after 45 seconds, the
ignition module locks out with the PURGE LED flashing indicating a pressure switch fault.
Is there continuity
T
hrough GREY
wire leads of heater side
safety circuit harness?
(see photo below)
N
Y
Is there continuity
t
hrough RED
wire leads of heater side
safety circuit harness?
(see photo below)
N
Check PURGE LED status.
Y
S
afety Circuit OK,
(see “Blower Testing
& Replacement”)
Replace exhaust
pressure switch (see
“Exhaust Pressure
Switch Replacement
Procedure”)
Replace vent safety
switch.
(see “Vent Safety
Switch Replacement
Procedure”)
C
all technical
support.
Y
N
Depress reset
button on vent
safety switch. Is
there continuity
across high limit
switch?
(see photo below)
Refer to
“Check Collector Pressure”
(see next page)
Check blower for proper
operation (see page 27)
Is blower OK?
N
Check PURGE LED status
on ignition module,
Flashing after 45 seconds?
On within 5 minutes? Pressure switch is OK.
Y
Y
Safety Circuit Trace
Does heater
function?
Verify proper
switch operation.
(see “Vent Safety
Switch Testing and
Replacement”)
N
Y
LED Status
Only power LED is on, or
Purge LED flashing.
Service Procedure EF-VI
Exhaust Pressure Switch Testing and Replacement
For serial numbers prior to “CF”
N
Flashing after
5 minutes?
Call for technical
support.
Correct blower problem
(see “Blower Testing and
Replacement”)
N
Y
Y
WARNING
1
20 volt potential exposure. Use caution
m
aking voltage checks to avoid personal injury.
Heater side
harness
Control side
harness
Reset button
54
54