Honeywell 7800 Series Manual page 17

Fault Code
Fault 68 Preignition Interlock fault.
*Preignition ILK*
Fault 69 - 70 Unused faults.
*Call Service*
Fault 71 Low Fire Switch closed, High
*Dynamic LFS* Fire Switch must be open
(EC/RM7850 only).
Fault 71 Limit input (terminal 7) is off
*Limits Complete* when it should be on (RM7888
only).
Fault 72 High Fire Switch closed; Low
*Dynamic HFS* Fire Switch must be open
(EC/RM7850 only).
Fault 72 Special Function 2 Input
*Spec.Func.2* (terminal 17) is off when it should
be on.
Fault 73 Special Function 3 Input
*Spec.Func.3* (terminal 19) is off when it should
be on.
Fault 75 Flame Indication Feedback
*Flame Proven (terminal 21) either on when it
Feedback* should be off or off when it
should be on.

Fault 76 - 93
*Accessory Fault*

Fault 94 - 104
*Call Service*
Fault 105 Relay Module self-test failure.
*Call Service*
Fault 106 Relay Module self-test failure.
*Call Service*
Fault 107 Relay Module flame signal
*Call Service* crosscheck failure.
Table 3. Hold and Fault Message Summary (continued).
System Failure
1.
2.
3.
4.
5.
6.

1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.
4.
1.
2.
3.


1.
2.
3.
7800 SERIES RELAY MODULES
Recommended Troubleshooting
Check wiring; correct any errors.
Inspect the Preignition Interlock switches and make sure
they work properly.
Check fuel valve operation. Valve must close within five
seconds.
Reset and sequence the relay module.
During STANDBY or PREPURGE, measure the voltage
between terminal 17 and G (ground). Supply voltage should
be present. If not, the Preignition Interlock switches are
defective and need replacing.
If the fault persists, replace the relay module.
Check firing rate position switches (usually in Modutrol®
Motor) for proper operation.
Check wiring, correct any errors.
Reset and sequence the relay module.
If the fault persists, replace the relay module.
Check limits to make sure they are satisfied after resetting.
Check electrical connections to terminal 7 of wiring
subbase.
Reset relay module.
If the fault persists, replace the relay module.
Check firing rate position switches (usually in Modutrol®
Motor) for proper operation.
Check wiring, correct any errors.
Reset and sequence the relay module.
If the fault persists, replace the relay module.
Check operation of Special Function 2 of PLC.
Check electrical connection to terminal 17 of wiring
subbase and confirm presence of supply power when
Special
Function 2 is activated.
Reset relay module.
If the fault persists, replace the relay module.
Check operation of Special Function 3 of PLC.
Check electrical connection to terminal 19 of wiring
subbase and confirm presence of supply power when
Special
Function 3 is activated.
Reset relay module.
If the fault persists, replace the relay module.
Remove wire to terminal 21 and reset relay module.
If the fault persists, replace relay module.
Reconnect wire to terminal 21. If the fault returns, verify
wiring.
Reset and sequence the relay module.
If the fault reappears, remove power from the relay module
and reapply the power; reset and sequence the relay
module.
If the fault persists, replace the relay module.
17
(continued)
65-0229—1