ENVIRO-TEC
36
FORM ET115.24-NOM11 (118)
FAN RELAY BOARD TROUBLESHOOTING GUIDELINES
Risk of Electric Shock.
Disconnect or isolate all power supplies before making electrical connections. More than one
disconnection or isolation may be required to completely de-energize equipment. Contact with
components carrying hazardous voltage can cause electric shock and may result in severe
personal injury or death.
No routine maintenance is required for the fan relay board.
TABLE F.10 - FAN RELAY BOARD TROUBLESHOOTING GUIDELINES
PROBLEM
POSSIBLE CAUSE
CORRECTIVE ACTION
No 24VAC power
Blown fuse onboard (F1)
Measure resistance across fuse:
• A properly working fuse will measure <1.0
Ω.
• A blown fuse will measure as an open circuit.
Replace fuse if blown using replacement fuse
identified above.
Incorrect incoming line voltage
Verify incoming voltage to the unit is within
tolerance.
Improper wiring connections
•
Verify that the unit is wired per the unit
wiring diagram for incoming voltage. If the
unit includes main fusing, verify that the
fuses are not blown.
• Verify wire harness connections are secure.
See “Checking Wire Harnesses” section.
JP2 removed without float switch
installed
Verify that either a float switch or JP2 are
installed. If neither, install one of them.
Float switch tripped
Verify float switch (if present) is made.
JP3 removed without external start/
stop control installed
Verify that either an external start/stop or JP3 are
installed. If neither, install one of them.
Damaged transformer
If all of the above are confirmed, replace the fan
relay board.
Fan motor will not run
No 24VAC power
See above.
Fan speed is not commanded.
Verify a fan speed is commanded from either
jumper JP1, a unit-mounted or remote-mounted
three speed switch, or a thermostat.
Electric heat signal
is not provided to
contactor
Fan speed is not commanded.
Verify that fan motor is running. A fan speed
must be commanded from one of these sources
to allow the electric heat contactor to energize
on a call for heat.
Outside Air Damper
actuator will not
energize
Fan speed is not commanded.
Verify that fan motor is running. A fan speed
must be commanded from one of these sources
to allow the damper actuator to energize.