Rheem · Furnace

2 blinks Pressure switch circuit open

Medium severity Rheem (-)GRC/(-)GTC 90 PlusRheem 90RJ/90TJ 90 Plus

What the control is telling you

Green STATUS LED blinks 2 times: the air-proving (negative) pressure switch circuit did not close or opened while the inducer was running.

Applies to: Rheem (-)GRC upflow and (-)GTC downflow/horizontal 90 Plus condensing gas furnaces (UT Electronic Controls 1012-925 / 1028-928 and Invensys ICC-H1MC7-01 IFC); Rheem 90RJ and 90TJ 90 Plus condensing gas furnaces (UT Electronic Controls 1012-925 or Invensys ICC-H1MC7-01 IFC, hot surface ignition)

Likely causes

Blocked vent or intake, or vent too long / too many elbows / too small
Blocked heat exchanger
Pressure switch hoses kinked, disconnected, or holding water
Inducer (IDM) wired wrong, weak, or bad capacitor
High wind opening the switch
On downflow 90+ units, auxiliary limit open (inducer wire runs through it)
Faulty pressure switch or wiring

Test and repair steps

Warning: Hazardous line voltage - disconnect power before servicing; work must be done by a trained, qualified service technician.
Confirm the inducer runs for the 30-second pre-purge; if not, check line voltage at the IDM, wires between IDM and IFC, line voltage on the IDM pins of the IFC connector, and the IDM capacitor (90+ only).
Check the pressure switch(es), hoses and wires; drain any water or moisture from switches and hoses.
Inspect vent and intake for blockage; verify vent length, number of elbows and pipe diameter are within the venting tables.
Check for a blocked heat exchanger.
Make sure the inducer is wired correctly and consider excessive wind at the termination opening the switch.
On downflow 90+ models check the auxiliary limit - it should be closed.
Watch for intermittent pressure switch operation during the ignition trial.

Settings for these units

Filter sizes (Table 12) · Rheem 90RJ/90TJ 90 Plus
Minimum clearance to combustibles · Rheem 90RJ/90TJ 90 Plus
Filter sizes (Table 9) · Rheem (-)GRC/(-)GTC 90 Plus
Minimum clearance to combustibles · Rheem (-)GRC/(-)GTC 90 Plus

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Source: Rheem (-)GRC/(-)GTC Installation Instructions 92-24161-88-00, Figure 56 IFC Troubleshooting Guide, p.54 (printed); Rheem 90RJ/90TJ Installation Instructions 92-24161-32-08, Figure 53 IFC Troubleshooting Guide, p.54 (printed p.53). Summarized in our own words; check the original manual for your model.

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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.