Cambridge Engineering S400

Questions and Answers

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Trevor WheelerAug 5, 2025
How to troubleshoot no blower operation in Cambridge Engineering S400?
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  pamelahallAug 5, 2025
  If the Cambridge Engineering Heater blower isn't running, first ensure the unit isn't in reset by turning it OFF and then ON again. Check that the heater disconnect is ON. Verify the mode selector switch on the RCS is in the correct mode and adjust the operating thermostat if needed. Make sure the blower service switch is in the REMOTE position. Examine the control and Class 2 transformers, checking the disconnect, supply fusing, and supply voltage. Also, inspect the multi-functional PC board, checking the voltage in the RCS. Other potential causes include the damper motor (adjust damper stroke), motor protection/starter/motor (check primary power source or replace starter), blower (replace bearings), or belts (tighten belts).
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Patricia DeanAug 9, 2025
What to do if Cambridge Engineering S400 Heater modulating valve does not modulate and runs on continuous high fire?
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  Desiree WoodAug 10, 2025
  If the Cambridge Engineering Heater's modulating valve is stuck on continuous high fire, try reinstalling the wire on the amplifier (A1014, A1044, or AD1014). You might also need to clean the Discharge Air Temperature Sampling Tube for the discharge temperature sensor (TS114J or TS144). For Series 44 models, replace the space temperature selector if resistance exceeds specified values (7,000 ? for T244; 5,500 ? for TS244; or 2,250 ? for TD244). For Series 14, recalibrate or replace the space thermostat. If using a remote heat adjust (TD114 or CEI 4175-0-960), replace it if resistance between terminals 1 and 3 is less than 6,000 ?.
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santiagojamesAug 13, 2025
What to do if Cambridge Engineering S400 Heater blower runs, but there is no heat and flame safety relay locks out?
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  murphylindaAug 14, 2025
  If the blower runs but the Cambridge Engineering Heater doesn't heat and the flame safety relay locks out, start by checking the igniter current. Also, check the gas supply for low or no gas pressure using the high or low gas pressure switches. Inspect the gas valve, verifying the FSR output to the R1 relay during ignition. Finally, adjust the minimum fire on the modulating valve.
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Dennis YoungAug 17, 2025
Why Cambridge Engineering S400 blower runs, unit heats, but will not cycle off?
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  Jesus ClarkAug 17, 2025
  If the Cambridge Engineering Heater blower runs, the unit heats, but it won't cycle off, first check the thermistor wiring and consider replacing the thermistor for the operating thermostat. Ensure the burner service switch is in the REMOTE position. Inspect the auxiliary circuit wiring and contacts. Consider reviewing the control system's operational characteristics to ensure proper understanding.
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Stephanie KellyAug 22, 2025
What to do if Cambridge Engineering S400 modulating valve does not modulate and runs on continuous low fire?
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  Emily GilmoreAug 22, 2025
  If the Cambridge Engineering Heater's modulating valve is stuck on continuous low fire, start by checking for a short in the modulating valve coil using the Class 2 transformer. If the valve coil resistance is less than 40 ? or greater than 85 ?, replace it. With the wire removed from terminal 3 of the amplifier, replace the amplifier if the valve voltage doesn't exceed 18 Volts DC. Replace the discharge temperature sensor (TS114J or TS144) if the resistance at terminals 1 and 2 on TS114J is less than 8,000 ?. Also, replace the space temperature selector (T244 or TS244/TD244) if the resistance is less than 5,000 ? for the T244, 3,500 ? for the S244, or 1,950 ? for the TD244.
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David WhiteAug 27, 2025
What to do if Cambridge Engineering Heater blower runs, but there is no heat and flame safety relay doesn’t lock out?
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  Brian MillerAug 27, 2025
  If the Cambridge Engineering Heater blower is running but there's no heat and the flame safety relay isn't locking out, first, ensure the mode selector switch is in the HEAT position. Then, check that the burner service switch is in the REMOTE position. After that, check the voltage in the RCS using the multi-functional PC board. You may also need to reverse the motor direction on the airflow switch. Finally, check the wiring of the flame safeguard relay.
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Ashley DavisAug 31, 2025
How to fix erratic or pulsating flame in Cambridge Engineering Heater?
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  Mrs. Sarah CampbellAug 31, 2025
  To address an erratic or pulsating flame in your Cambridge Engineering Heater, start by enlarging the vent piping size or reducing the vent piping length for the high-pressure regulator. Then, adjust the sensitivity control dial on the amplifier counter-clockwise. For the space temperature selector (T244 or TS244/TD244) and remote heat adjust (TD114 or CEI 4175-0-960), use shielded, twisted pair wiring.