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Rheem · Furnace troubleshooting

ECM blower will not run - power and communication checks (code 68)

R96V/96MDV

What is going on

The communicating blower motor does not start on a heat, cool or fan call and the control shows 68.

Likely causes

  • No 115-120 VAC at the motor line connector
  • Pins not seated in the 5-pin or control connector
  • Control cable between P5 and the motor damaged
  • Failed motor module

Check in this order

  1. Unplug the 5-pin line voltage connector at the motor. With the door switch closed, check for 115-120 VAC between pins 4 and 5; line voltage should be there whenever the furnace is powered. No voltage: fix the wiring. Make sure every pin is fully seated, then plug it back in.
  2. Unplug the motor control connector from P5 on the control and put 24 VAC on pins 3 and 4 of the motor side. With the door switch closed the motor should run at about 75%.
  3. Motor runs in that test the problem is the control or the control cable, not the motor.
  4. Motor does not run check the control cable end to end and pin seating; if the wiring is good, replace the motor.

Applies to: (-)96VA040-115 (R96V / U96V) and (-)(-)96MDV040-115 two-stage variable-speed communicating furnaces

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Source: Rheem (-)96V / (-)(-)96MDV Installation Instructions 92-24161-124-08, Diagnosing blower motor issues p.122, Fig. 62. 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.