The main reasons why the frequency speed control small diaphragm pump fails to be debugged and the troubleshooting process

Some customers may not know much about frequency speed adjustment for the small diaphragm pump.  I’d like to summarize for you how to troubleshoot when the frequency speed control type cannot control the speed.

Taking our C26, C30, D35, and S36 series frequency speed regulation models as an example, the reasons for unsuccessful frequency speed regulation are:

1. Pump circuit board failure;

2. The alarm does not work due to incorrect voltage;

3. Enable signal and working condition memory issues;

4. Poor wiring or incorrect wiring;

5. The input signal does not meet the specifications.

Troubleshooting step 1:

If it is powered on and running, observe the indicator light and it flashes green, then the circuit board fault is eliminated and go to step 3;

Otherwise, go to step 2;

Troubleshooting step 2:

When the power is on, the small diaphragm pump is not running and there is no operating noise. At this time, the working condition indicator light on the small diaphragm pump panel can be observed.

The green light is always on. Go to step 3;

The red light is always on. Go to step 4;

Red light flashes. Go to step 5;

Troubleshooting step 3: (Green light is always on for the small diaphragm pump)

The power green light is always on, which means the power is normal but the small diaphragm pump is in shutdown state. There are two possibilities.

(1) EN is left floating or high, and the small diaphragm pump operates according to the last memorized working condition, and the memorized working condition is pause;

(2) EN is low level and operates according to the FRE input signal. The FRE input signal is lower than the 100Hz shutdown signal;

small diaphragm pump

In both cases, EN should be suspended and the status of the small diaphragm pump should be observed. If it returns to normal, proceed to step 6;

Troubleshooting Step 4: (The red light is always on)

Remove the hoses from the air inlet and exhaust port of the small diaphragm pump and allow the small diaphragm pump to return to normal pressure and low load. After disconnecting the power supply, power it on again. If it returns to normal, go to step 6;

If the red light is still on, return it to the factory for inspection;

Troubleshooting step 5: (Red light flashes)

Disconnect the power input of the small diaphragm pump and use a multimeter to check whether the power supply input voltage is consistent with the voltage on the pump nameplate; if it is consistent, reconnect the power input and start the small diaphragm pump, and observe whether the voltage drops significantly at the moment of power-on, and then the indicator light changes from green to green. The red light flashes. If yes, it means that the power of the power supply is insufficient.

The voltage drop at the moment of startup is too large, and the power supply should be replaced. If the voltage is normal and the pump enters the red light flashing state after running for a period of time, it means that there are occasional power fluctuations and glitches. To alarm, you need to check the power quality or whether there are other interfering devices on the same power supply, such as high-power motors, solenoid valves and other equipment;

Troubleshooting Step 6: (After eliminating the above faults, enter the signal debugging stage)

First connect EN to ground, keep EN always valid, then start debugging the FRE signal, after connecting EN to ground, connect FRE to ground, does the small diaphragm pump stop? If it stops, the green light is always on, which means the wiring is normal, go to step 7; if it does not stop, or other indicator lights appear, you need to check whether the EN and FRE line sequence, wiring harness, and connections are correct and good;

Troubleshooting step 7:

Keep EN grounded, input 3000Hz square wave to FRE for 10 seconds, and then input 2000Hz square wave for 10 seconds. Observe whether the small diaphragm pump rotation noise changes significantly and whether the green light flashing frequency changes significantly. If there is an obvious change, it means the speed adjustment is successful. If there is no change, use Check the FRE square wave signal with an oscilloscope. The recommended amplitude value is 5V, the bias voltage is 2.5V, and the duty cycle is fixed at 50%;


Before using our small diaphragm pump, customers can contact our staff for detailed instructions, and follow the recommendations in our instructions for wiring and signal output. If you have any questions, you can also contact our pre-sales staff by phone to help you solve it.

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