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Troubleshooting
All service troubleshooting must be performed by trained, qualified contractors or technicians. A
volt/ohm meter is required for proper diagnosing. A clamp-on amp meter is also very helpful.
1. Green LED 1 flashing two pulses every two seconds – this indicates the control board cannot read
temperature sensor. Verify temperature sensor wire connections. If secure, replace sensor.
2. No heat –
Green LED 1 off:
a) Verify temperature set point. If the incoming air is higher than set point, the element will
remain off. Adjust temperature set point to a higher setting and verify element comes on
with amp meter.
b) If incoming air temperature is less than set point, disconnect the red/black/white sensor
wires.
1) If the unit starts heating and green LED 1 is pulsing, replace the temperature sensor
2) If green LED 1 remains off, replace the control board
Green LED 1 on:
a) Verify incoming 120-volt power. The 24VAC control voltage is typically sourced
separately.
b) Verify 120-volt across element terminals.
1)
If 120-volt is present, shut off the power source and disconnect element wires to verify
element resistance. A good element should measure approximately 14 ohms.
2)
With 120V source power turned on and no 120-volt directly across the element, check
the following points referencing UAW881:
a) Measuring across limit switch, 0V (closed) indicates the limit is okay. Measuring
120V (open), limit is bad or sensing temperatures are over 120°. With power
disconnected, check ohms. If limit is below room temperature open line (OL) this
indicates limit is bad.
b) Measuring terminal where B/W lands on triac relay to ground – 120V is possible
bad triac, OV is possible bad control board.
3. Not enough heat –
a) Check amperage draw. Approximately 8.33 amps means the element is at full power.
b) Verify CFM and temperature rise. CFM's over 100 will result in 30° or less temperature
rise. Cold incoming air will be warmed based on the CFM Temperature Rise Chart on the
attached document EL910.
04/27/2021
4
EI912
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