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Johnson Controls A419 Troubleshooting - PartsAPS

johnson controls a419 troubleshooting

Johnson A419 Temperature Controller is designed to control HVAC equipment under normal operating conditions. Where failure or malfunction of a Johnson A419 temp control could cause damage to the equipment or other devices like limit or safety controls. If you have issue with your controller, check out our Johnson Controls A419 troubleshooting tips.

Johnson Controls A419 Troubleshooting Guide

Johnson Temperature Control A419 series can be used to control a wide variety of single-stage HVAC or refrigeration equipment. Typical applications include:

  • Retail stores display freezers, walk-in coolers, and reach-in coolers.
  • Space and return air temperature control.
  • Supermarket display cases for products.
  • Cooling tower pump and fan control.
  • Condenser fan cycling or staging.
  • Boiler operating control, used as a thermostat.

Johnson A419 Troubleshooting

If your Johnson controls A419 not working properly, you have to verify it's wiring, and configuration. Also, check whether it is set properly or not. If all these are in good condition, but the problem persists, try the following procedures to determine the cause of the problem.

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Check for proper supply voltage to the control

To verify if the Johnson temperature control is receiving proper voltage, go through the below steps.

  • Loosen the four captive cover screws for removing the cover.
  • You have to use a reliable AC voltmeter to check the voltage between COM and 120/ 240V terminals on line voltage models. And, verify between the two 24V terminals on low voltage models.
  • The voltage reading must be between 177-264 VAC for 208/240-volt applications, 102-132 VAC for 120-volt applications, and 20-30 VAC for 24-volt applications.
  • If the voltage reading is not within the specified range, check the power source & input power wires.

Check for proper sensor operation

  • Before going to verify the operation of the sensor, you should disconnect all power sources to control.
  • By using an accurate thermometer, you have to note the temperature reading at the sensor location.
  • Now, disconnect the sensor from control.
  • Using an ohmmeter, measure the resistance across the two sensor leads while the sensor is at the temperature taken as before step.
  • Refer to the manual to verify that the measured temperature and resistance matched with established temperature and resistance values.
  • If the sensor's measured resistance value is different from the expected value for that temperature, then, your job is to inspect the sensor wiring. If that wiring is okay, you will go through the sensor replacement.

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Check for proper operation

  • First, you should remove the load from output relay terminals.
  • Make sure that the touchpad lock jumper is installed so that the touchpad is unlocked.
  • Now, reconnect the sensor leads and supply power to the control.
  • Replace the cover.
  • Verify the control settings for correct values.
  • Press & hold the "Menu" button until you notice "Setpoint”.
  • You have to use "Up and Down" buttons to change the Setpoint temperature above and below the current sensor temperature until the output relay energizes and de-energizes. You can see this energize and de-energize values table in the manual.
  • The relay doesn't energize until the timed delay has decreased when the anti-short cycle delay time is greater than zero minutes.
  • If the output relay does not perform as indicated in the reference manual, you will need to replace the temperature control.
  • Once the operation of the A419 control is verified, you need to reconnect the load and check the manufacturer’s instructions for troubleshooting the controlled equipment.

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Mounting Instructions

To avoid installation instructions, refer to the below steps and know the correct mounting process.

A Johnson A419 controls has either a NEMA 4X corrosion-resistant watertight or standard high-impact plastic NEMA 1. This control is not position sensitive, but you should mount it for convenient wiring and adjustment.

When mounting the A419 temp control to rigid conduit, you need to attach the hub to the conduit before securing the hub to the control enclosure.

NEMA 1 mounting hole pattern is identical to that of the system 350 controls and models of the A19 control. The NEMA 1 enclosure can be mounted on a 35 mm DIN rail. The NEMA 4X models will be mounted on flat vertical surfaces using the four screw holes at the enclosure corners.

Use a conduit fitting rated for the environment in which the control is installed to maintain the watertight and corrosion-resistant integrity of the NEMA 4X enclosure.

An additional two-wire cable is needed to operate the temperature offset function. For NEMA 4X enclosures, you should install a suitable liquid tight-fitting in an available knockout to pass the two-wire cable through the enclosure wall.

In addition to the mounting instructions, you should know how to wire Johnson controls a419. Refer to the owner’s manual to get wiring instructions.  


That's all about the Johnson Controls A419 troubleshooting procedure. If your system doesn't work even after performing the above steps, contact an authorized Johnson Controls technician. We hope this guide helped you to finish your job quickly and easily. Stay in touch with us to get more troubleshooting guides on HVAC equipment and their components.

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