Form O-Y P/N 273647R5, Page 35
Vent Temperature Limit Switch (High Efciency Models Only)
The vent temperature limit switch is located on the discharge of the combustion air
blower (venter) and its purpose is to prevent the vent gas temperature from exceed-
ing a temperature that will harm the PVC vent pipe. If the vent temperature limit
switch is activated, the cause must be determined and corrected before the heater
is placed back into operation. Activation of the manually reset vent temperature limit
switch could be caused by one or more of the following:
□ Manifold gas pressure too high
□ The heat content of the fuel being burned is too high
□ Reduced circulating airow due to dirty and/or plugged air moving components
□ Excess dirt on the heat exchangers
□ Failed heat exchanger(s)
After the cause is determined and corrected, depress the red button on the switch to
reset it.
Vent Temperature
Limit Switch
IMPORTANT: When using a multimeter to troubleshoot the 24 volt circuit, place the
meter’s test leads into the 5 or 9 pin connectors located on the ignition control. Do not
remove connectors or terminals from the electrical components. Doing so can result
in misinterpreted readings due to the ignition control board’s fault mode monitoring
circuits.
LED Flash Codes for
DSI Control Module
Flash Code Description
Fast Flash Normal operation
Steady OFF No power, blown fuse, or defective board
1 Low pressure switch stuck open
2 Low pressure switch stuck closed
3 High pressure switch stuck open
4 High pressure switch stuck closed
5 Limit switch open
6 Ignition lockout (failed ignition)
7 Too many (5) limit switch losses
8 Too many (5) ame losses
9 Too many (3) high pressure switch losses during one call for heat
DSI Control Module
P/N 272626
LED Light
Only replaceable part is a Type ATC or ATO
3 amp fuse (color code violet), P/N 201685.
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