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Troubleshooting
Heater Does Not Operate (Pilot Ignition)
Does not attempt to light (No visible spark)
24 VAC between
terminals W1 and X?
Yes
115 VAC between
terminals 102 and 101?
Yes
115 VAC between
terminals 103 and 101?
Yes
115 VAC between
terminals 104 and 101?
Yes
115 VAC between
terminals 106 and 101?
Yes
Continuity between
terminals 107 and 108?
Yes
No
No
No
No
No
No
Heat switch (S4) off.
Turn heat switch (S4) on.
Heat switch not wired.
Wire heat switch (S4).
Primary fuses blown.
Replace fuses.
Main transformer (TR4) defective.
Replace transformer.
(Optional) inlet air sensor (TS4) holding.
Adjust TS4 setting.
Reference:
Heat relay (RH) defective.
Replace heat relay (RH).
The power light on the flame safeguard should
blink approximately every 5 seconds as it
performs a
High limit (HLC1) tripped.
Reset or replace high limit (HLC1).
Check on cause of control loss.
(Optional) high/low gas pressure switch(es)
(PS3 and PS4) tripped.
Correct gas pressure and reset.
Reference:
Airflow switch (PS2) holding for proper airflow.
Correct airflow across burner.
Reference:
Check the Optional High and Low Gas Pressure Switches, pg. 15
At this time the heater should attempt to light.
The pilot light on the flame safeguard should illuminate.
26Model VSU
®