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ICP · Furnace troubleshooting

No heat - control does not respond to thermostat

What is going on

LED heartbeat, no stored codes, but furnace does not respond.

Likely causes

  • Thermostat or thermostat cable fault
  • Thermostat not compatible with the control
  • Failed furnace control

Check in this order

  1. Check for 24 V at W/W1, W2, Y1, Y/Y2 or G on the furnace control during a call.
  2. No 24 V: check the thermostat and cable.
  3. 24 V present but no response: disconnect all thermostat wires and jumper R to W/W1 etc.
  4. If it works with a jumper, the thermostat is not compatible: add a ballast resistor, connect Com24V to the thermostat, or replace the thermostat.
  5. If it still does not respond with a jumper, replace the furnace control.

Applies to: ICP F9MAE / G9MAE modulating variable-speed condensing gas furnaces (060, 080, 100, 120 kBtu/h)

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Source: ICP (F/G)9MAE Service and Technical Support Manual 440 04 4700 00, Figure 16 Troubleshooting Chart, p.33. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.