Wiring Diagram: How to Jump a 3-Wire AC Pressure Switch
This guide explains how to jump a 3-wire AC pressure switch, a common troubleshooting step for air compressors and other pressure systems. Important Safety Note: Before working with any electrical component, always disconnect the power supply. Failure to do so could result in serious injury or death. If you are uncomfortable working with electrical systems, consult a qualified electrician.
This process is primarily used for testing purposes to determine if the pressure switch itself is faulty. Jumping the switch bypasses its internal pressure mechanism, allowing you to test the compressor's motor and other components independently. This should only be a temporary solution for diagnostic purposes; a faulty pressure switch should be replaced.
Understanding the 3-Wire AC Pressure Switch
A typical 3-wire AC pressure switch has three terminals:
- L (Line): Connected to the power source.
- C (Common): Connects the L and T terminals, completing the circuit when the pressure is within the correct range.
- T (Terminal): Connected to the compressor motor.
How to Jump a 3-Wire AC Pressure Switch
The goal is to create a continuous circuit between the L and T terminals, bypassing the pressure-sensing mechanism. This is achieved by temporarily connecting these two terminals with a suitable jumper wire.
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Identify the Terminals: Locate the L, C, and T terminals on your pressure switch. The labeling might be slightly different (e.g., using numbers instead of letters), but the function remains the same. Refer to your specific pressure switch's documentation for clarification if needed.
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Prepare the Jumper Wire: Use a short length of appropriately-rated insulated wire. The wire gauge should match or exceed the wire connected to the pressure switch. Strip a small amount of insulation from both ends of the wire. Ensure you are using insulated wire to prevent shorts and potential hazards.
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Connect the Jumper: Carefully connect one end of the jumper wire to the L terminal and the other end to the T terminal. Ensure a secure connection to avoid accidental disconnections.
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Reconnect Power: Carefully reconnect the power supply to the system. The compressor motor should now start running continuously.
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Observe the Operation: Monitor the compressor's operation carefully while it's running continuously. Listen for unusual noises or other issues. This step helps determine if the issue lies with the motor, other components in the system, or indeed the pressure switch.
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Disconnect Power & Remove Jumper: After your observations, immediately disconnect the power supply and remove the jumper wire. Never leave the jumper wire in place during normal operation.
What if the Compressor Still Doesn't Run?
If the compressor still doesn't run after jumping the pressure switch, the problem likely lies elsewhere in the system, such as:
- Faulty Compressor Motor: The motor itself may be burned out or otherwise damaged.
- Wiring Problems: Check for loose connections or damaged wiring between the pressure switch and the compressor motor.
- Overload Protection: A circuit breaker or thermal overload switch may have tripped.
What if the Compressor Runs Continuously After Jumping?
If the compressor runs continuously, it is highly probable the pressure switch is faulty and needs replacement. The pressure switch is failing to detect the pressure level, therefore the compressor continues to run.
Why you shouldn't leave the jumper wire in place
Leaving the jumper wire in place will cause the compressor to run continuously until the tank pressure reaches a dangerous level. This could cause serious damage to the system, as well as posing a safety hazard. The pressure switch is a critical safety component; never bypass it permanently.
Replacing the 3-Wire AC Pressure Switch
If you've determined that the pressure switch is faulty, it's crucial to replace it with a compatible model. Consult your air compressor's manual or the pressure switch's specifications to ensure you choose the correct replacement. Remember to follow all safety guidelines when replacing the switch and reconnect the wiring according to the manufacturer's instructions.
This guide provides a general understanding. Always consult the specific instructions for your model. Incorrect wiring can damage equipment or create safety hazards.
