43AP Pneumatic Controller - Automation Service

43AP Pneumatic Controller

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September 8, 2023

Troubleshooting a 43AP Pneumatic Controller

The Foxboro 43AP Pneumatic Controller is a versatile instrument that can be used to control process variables, including pressure, temperature, flow, and level. It does this by continuously measuring the difference between the current process value and the desired set point, and then generating an output air signal that is proportional to this difference. The type of control determines how the output air signal is used to control the process variable.

While the 43AP is reliable, like any piece of equipment, it can experience problems from time to time. This piece will walk through troubleshooting the 43AP Pneumatic Controller.


ISSUE: No Reading (Or Very Low Reading) At Output Gauge

If the output gauge on your 43AP controller is not reading properly, there are a few things you can check. First, make sure that the controller is receiving the correct air pressure. The 43AP controller requires 140 kPa (20 psi) of air pressure. If the air pressure is too low, the controller will not be able to operate properly.

Next, check the measurement reading on the controller. If the measurement reading is also low or inaccurate, then there may be a problem with the controller’s sensor. You can try cleaning the sensor or replacing it if necessary.

If the air pressure and sensor are both okay, then the problem may be with the controller’s output line or valve motor. You can disconnect the output line and plug the controller output with your finger to see if there is any air flow. If there is no air flow, then there is a leak in the output line or valve motor.

ISSUE: Maximum Pressure At All Times At Output Gauge

If the output gauge on your 43AP controller is always reading maximum pressure, then there are a few things you can check. First, make sure that the controller is not damaged or leaking. If the controller is damaged, it may be causing the nozzle to always be covered by the flapper.

Next, check the relay gasket to make sure that it is not misaligned. A misaligned relay gasket can cause the nozzle to be plugged, which will result in maximum pressure at the output gauge.

If the controller is not damaged and the relay gasket is not misaligned, then you may need to replace the relay. The relay is a small electrical component that controls the output of the controller. If the relay is faulty, it can cause the output gauge to read maximum pressure.

These are just a few common troubleshooting tips for the 43AP pneumatic controller. If you are experiencing problems with your controller, consult Foxboro’s manual for more detailed instructions. You can also contact the product experts at Automation Service.