This guide explains how to jump a 3-wire AC pressure switch, a common troubleshooting step for air compressors and other pressure-sensitive systems. While this is a temporary fix for testing purposes, it's crucial to replace a faulty switch permanently. Improper wiring can lead to damage or injury. Always disconnect power before working on any electrical components.
Understanding the 3-Wire AC Pressure Switch
Before we jump into the wiring, let's understand the three wires typically found on an AC pressure switch:
- Common (C): This is the neutral wire, usually connected to the power source.
- High Pressure (HP): This wire connects to the compressor motor and is activated when pressure reaches the high-pressure setting.
- Low Pressure (LP): This wire also connects to the compressor motor, but is activated when pressure drops to the low-pressure setting.
The switch uses these connections to turn the compressor motor on and off based on system pressure.
How to Jump a 3-Wire AC Pressure Switch for Testing
Jumping the switch involves bypassing the internal mechanism to test if the compressor motor and other components are working correctly. This is done by connecting the HP and LP wires together directly. This only tests the motor and circuit, not the pressure switch itself.
Here's how to do it:
- Safety First: Ensure the power supply to the compressor is completely disconnected.
- Locate the Wires: Identify the Common (C), High Pressure (HP), and Low Pressure (LP) wires on your pressure switch. Consult your compressor's manual if needed. The wires may be color-coded.
- Prepare Jumper Wires: You'll need a short length of insulated wire, preferably the same gauge as the wires on the pressure switch.
- Connect the Jumper: Carefully connect one end of the jumper wire to the HP terminal and the other end to the LP terminal. This effectively bypasses the switch, allowing continuous power to the compressor motor.
- Reconnect Power: Reconnect the power supply to the compressor.
- Observe the Motor: Check if the compressor motor starts running. If it does, this indicates that the motor itself is functional and the problem may lie with the pressure switch. If it doesn't, then the motor or some other part of the system may be faulty.
Important Note: The compressor will run continuously when the switch is jumped. Never leave the compressor running for extended periods with the switch bypassed; this will cause pressure buildup and potential damage.
Why Your 3-Wire AC Pressure Switch Might Fail
Several reasons can cause your pressure switch to fail. Understanding these potential issues is crucial for diagnosing the problem accurately:
- Pressure Switch Wear and Tear: Like any mechanical component, pressure switches can wear out over time, losing their sensitivity to pressure changes.
- Contaminants: Dirt, debris, or moisture can enter the switch and interfere with its proper functioning.
- Overpressure: A pressure surge beyond the switch's operating limit can damage the internal components.
- Electrical Problems: A short circuit or other electrical fault can disable the pressure switch.
- Loose Wiring: Improperly connected or loose wires can cause intermittent operation or total failure.
What to Do After Jumping the Switch
Once you've completed the jump test, remember to:
- Disconnect the Jumper Wire: Carefully disconnect the jumper wire after testing.
- Assess the Results: Determine the cause of the problem based on the motor's reaction to the jump test.
- Replace the Switch: If the compressor motor runs correctly when the switch is jumped, it's highly likely that the pressure switch needs replacing. Do not continue to operate the system with the switch bypassed.
Troubleshooting Further Issues
What if the compressor motor doesn't start even when jumped?
If the motor doesn't run after jumping the switch, the problem lies elsewhere in the system. Potential causes include a faulty motor, blown fuse, tripped breaker, or a problem within the compressor itself.
What if the pressure switch only has two wires?
A two-wire pressure switch typically only controls the activation and deactivation of the motor based on pressure. The common (C) wire is integrated into the power supply. The procedure may vary slightly, but the principle of testing remains similar.
Remember, working with electrical components can be dangerous. If you're not comfortable performing these checks, seek assistance from a qualified technician. This guide is for informational purposes only. Always prioritize safety and consult your equipment's manual for specific instructions.
