Rexotherm Equipment Troubleshooting

Issue A: Fan Motor Will Not Start

  1. Check the power cord with a voltmeter for 115 volts. (Minimum 100 volts) If the power is low, a Buck N Boost may be used to increase the voltage by 10%.
  2. Check the ON/OFF switch is in ON (UP) position. Check the switch for 115 volts with a voltmeter on the black wired terminals.
  3. Push down the black contactor with a screwdriver. If the unit starts, the fan motor is defective or there is an issue with the wires between the contactor and the fan motor. If the unit does not start, the contactor may be defective. Check for 115 volts on the rear terminals of the contactor to verify power to it.
Image of power cord
Electric on/off switch

Issue B: Fan Motor Starts And Runs, But Stops When Start Actuator Is Released

  1. Remove the wires from the Air Proving Switch and connect together. Try to restart the heater. If the heater ignites, turn the adjusting screw on the Air Proving Switch counter-clockwise to reduce the sensitivity. Reconnect the wires to the safety switch.
  2. If the heater does not ignite, check the two copper tubes running from the Air Switch and make sure they are clear of debris.
  3. If the copper tubes are clear, check the Timer between 5 – 8 and 4 – 1 for OHM resistance. Replace Timer if necessary.
  4. Some heaters have a reset button on the motor. Make sure the button is pushed in.
Air switch jump
Air switch screw

Issue C: Heater Ignites, Runs For 5 Seconds, And Shuts Off

  1. Remove the side panel and check the wires on the High Limit Switch
  2. Remove the wires from the Air Proving Switch and connect together. Try to restart the heater.
  3. If the heater ignites, the High Limit Switch needs to be replaced.
  4. Check voltage of the black wires on the On/Off Switch. The On/Off Switch can be bypassed by connecting these two wires together.
Air switch jump
High temperature
Electric on/off switch

Issue D: Fan Motor Starts And Runs, But There Isn’t A Spark

  1. Check the Spark Plug Wire is connected between the Spark Plug and the Transformer. Make sure the Spark Plug Cap is tight onto the Spark Plug.
  2. Check the Transformer for an arc spark. Remove the front cap. Rest a screwdriver shaft on the side of the metal control box and tough the end of the screwdriver to the front of the Transformer. There should be an arc spark, verifying that the Transformer is working.
  3. If the Transformer is working properly, check the green Relays on the control board. Remove one at a time and attempt to start the heater or use a OHM Meter to check continuity between the copper prongs.
Spark plug

Issue E: Fan Motor Starts And Runs, There Is Spark, But No Flame

  1. Check the gas supply is on and all valves are open. Check for any kinks in the hose.
  2. Solenoid could be stuck. Rap on the fuel train to free up the Solenoid, while starting the unit.
  3. Check the burner orifices for plugging.
  4. Check the Solenoids for magnetism by placing a flat-head screw driver just above the metal post.
  5. If a Solenoid is defective, they can be taken apart and lubricated.
First stage regulator valve

Issue F: The Heater Runs, But The Spark Continues

  1. The heater is not sensing flame. Check that the Flame Rod is not resting on the burner and that it is clean.
  2. Check that the Flame Rod Wire is connected securely.
  3. Replace the Flame Pak.
  4. Check the Transformer for spark.
  5. Check the Thermal Circuit Breaker for applicable models.
Flame rod
Flame pak
Start actuator
Figure 7: flame rod test showing burner and spark plug location
Figure 7 shows the flame rod is a minimum 1/2" away from the burner. The arrow denotes the position of the spark plug. The Rexotherm will continually spark for the first 5 seconds, until the burner is lit.
Button and light with text "reset when l ight is off"
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