TROUBLESHOOTING

DIAGNOSTIC TABLE

DS 1 (Red)

DS 2 (Green)

Error/Condition

Comments/Troubleshooting

 

 

 

 

Simultaneous

Simultaneous

Normal operation

No fault

slow flash

slow flash

 

 

 

 

 

 

Simultaneous

Simultaneous

Normal operation with

Normal operation

fast flash

fast flash

call for heat

 

 

 

 

 

Slow flash

On

Open limit switch

Verify continuity through rollout switch circuit

 

 

 

 

Off

Slow flash

Pressure switch stuck

Pressure switch stuck closed. Check switch function, verify

 

 

closed/open

inducer is turning off.

 

 

 

Pressure switch stuck open. Check pressure switch function

 

 

 

and tubing. Verify inducer is turning on and pulling sufficient

 

 

 

vacuum to engage switch.

 

 

 

 

Alternate

Alternate slow

External lockout

Failure to sense flame is often caused by carbon deposits on

slow flash

flash

(retries)

the flame sensor, a disconnected or shorted flame sensor

 

 

 

lead or a poorly grounded furnace. Carbon deposits can be

 

 

 

cleaned with emery cloth. Verify sensor is not contacting the

 

 

 

burner and is located in a good position to sense flame.

 

 

 

Ignitor must be positioned to light the gas immediately when

 

 

 

the valve opens. If the ignitor has been replaced, verify hot

 

 

 

spot position has not changed.

 

 

 

Check sensor lead for shorting and verify furnace is

 

 

 

grounded properly.

 

 

 

 

Slow flash

Off

Flame sensed with gas

Verify the gas is operating and shutting down properly. Flame

 

 

valve de-energized

in burner assembly should extinguish promptly at the end of

 

 

 

the cycle. Check orifices and gas pressure.

 

 

 

 

On

Slow flash

Open rollout switch

Verify continuity through rollout switch circuit.

 

 

 

 

On

On

Module – internal fault

Module contacts for gas valve not operating or processor

 

 

condition

fault. Reset control, if condition persists, replace module.

 

 

 

 

Slow flash

Fast flash

Low flame sense

Low flame sense current is often caused by carbon deposits

 

 

current

on the flame sensor, a poorly grounded furnace or a mis-

 

 

 

aligned flame sense probe. Carbon deposits can be cleaned

 

 

 

with emery cloth.

 

 

 

Check or improve furnace and module ground. Verify sensor

 

 

 

is located in or very near flame as specified by the appliance

 

 

 

manufacturer.

 

 

 

 

Fast flash

Slow flash

Grounding or

Verify the control and furnace are properly grounded. Check

 

 

reversed polarity

and reverse polarity (primary) if incorrect.

 

 

 

 

Alternate fast

Alternate fast

Module ignitor

Fault code indicates the module ignitor contacts are not

flash

flash

contact failure

functioning properly. Replace module.

 

 

 

 

Homeowner Help Line: 1-800-284-2925

White-Rodgers is a business of Emerson Electric Co.

The Emerson logo is a trademark and service mark of Emerson Electric Co.

www.white-rodgers.com www.emersonclimate.com

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White Rodgers 50A66-743 installation instructions Troubleshooting, Diagnostic Table

50A66-743 specifications

The White Rodgers 50A66-743 is a state-of-the-art heating and cooling thermostat designed for maximum comfort and efficiency in residential environments. This versatile device is known for its reliability and user-friendly features, making it a popular choice among homeowners and HVAC professionals alike.

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