78
Diagnostics
FIGURE 47 (cont.)
DIAGNOSTICS FLOWCHART
ST -A1194-66-00
Check to make sure test mode dip switches are properly set.
- Check a ll connections between IFC and ECM motor.
- Check 24V to ECM Motor. (low voltage connector, pins 1 & 4)
- Check P.F.C. Choke. (except 1/2 HP motors)
- Check a ll wiring and connections
to P.F.C. choke.
- Check faul t code displ ay and see “faul t codes” In I & O.
Does I. B. M . energize at High speed?
After Blower on delay, Does IDM switch to High speed
and remain at low speed after switching?
Does furnace
continue to operate at high
fire until T-stat satisfied or heat call
removed?
Ensure T-stat not
switching to low fire or
test mode not timing out
(1 hour limit)
Fault code displayed?
See FAULT CODES under
troubelshooting in the I & O Manual
Does IDM Shut off after post purge?
Does I. B. M . shut off after 90 seconds? (pl us slew)
Double check - is heat call
completely off at IFC?
** System will attempt to light 4 times. Voltage Is present at gas val ve for
only 7 seconds during each ignition trial. System will enter a 1 hour
lockout after 4 attempts.
Remove heat call by setting
T-stat below room temp.
Remove power to furnace, open blower compartment
and restore dip switches to original settings. Replace
blower door. Restore power to unit.
- Check wire and all connections between I.F.C.and I.D. M
- Check for 115 VAC on P3-1 & P3-3.
- Check I .D.M . capacitor.
- Check I .D.M . low speed. Replace if neccessary.
C
PROBLEM PERSISTS
REPEAT THIS SEQUENCE UNTIL TROUBLE- FREE OPERATION
STEADY HIGH HEA T
Low
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