ECM blower does not start on high heat after burners light

What is going on

Use this check when the burners light but the ECM blower does not start roughly 15 to 20 seconds later on high heat. Turn the power off before touching connectors or harnesses, and confirm 115 VAC and 24 VAC readings carefully with a meter, since both are present on the board. Do not assume the motor is bad. In many cases it is a connector, a dip switch setting or low voltage to the motor. Work in order and write down each reading.

Likely causes

• Loose or bad connections between control and ECM motor
• Missing 24 VAC to the ECM control
• Dip switch setting wrong
• PFC choke wiring or failure
• Low line voltage to motor

Check in this order

1. Check all connections between the control and the ECM motor with power off
2. Check 24 VAC to the ECM control (4-pin connector, pins 1 and 4)
3. Check dip switch settings against the instructions
4. Check the PFC choke and its wiring, if present
5. Check fault codes shown on the display
6. Check line voltage to the motor (115 VAC)
7. Make sure test mode dip switches are set correctly before continuing
8. Return to normal dip switch settings when finished

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