1. Verify the Jump: Double-check that you've correctly jumped the low-pressure switch. You need to ensure a good electrical connection is made, bypassing the switch completely. A poor connection will give a false negative.
2. Power Supply:
* Breaker/Fuse: Check the circuit breaker or fuse supplying power to the compressor. It might have tripped or blown.
* Wiring: Inspect the wiring leading to the compressor for any damage, loose connections, or corrosion. A broken wire anywhere in the circuit will prevent operation.
* Power Source: Make sure the power is actually on at the main power source. Seems obvious, but it's easy to overlook.
3. Compressor Motor:
* Motor Capacitor (if applicable): Many compressors use a capacitor to help start the motor. A faulty capacitor will prevent the compressor from starting. This usually requires testing with a capacitor tester.
* Motor itself: The motor could be burned out or seized. This is more difficult to diagnose without specialized tools or experience. You might hear a humming sound if it's seized, but no actual turning.
* Thermal Overload: Some compressors have a thermal overload protector that shuts down the motor if it overheats. This may need to cool down before attempting to restart.
4. Unloader Valve (if applicable): Some compressors have an unloader valve that releases pressure when the compressor is off. A faulty unloader valve might keep the compressor from starting.
5. Pressure Switch (despite jumping it): While you jumped it, the issue *might* still reside within the wiring to the pressure switch, not the switch itself.
6. High-Pressure Switch: The high-pressure switch is a safety device that cuts power if pressure gets too high. If this switch is faulty, it might be preventing the compressor from starting. It's usually found near the high-pressure side of the system.
7. Other Components (Refrigeration Systems): If this is part of a larger refrigeration system (like an AC unit or refrigerator), the problem could be elsewhere in the system, such as a refrigerant leak, clogged filter drier, or another malfunctioning component.
What to do next:
* If you're not comfortable working with electricity or refrigeration systems: Call a qualified HVAC technician or appliance repair professional. Improperly working on these systems can be dangerous.
* If you are comfortable: Systematically check each item above, using a multimeter to test voltage and continuity at various points in the circuit. This requires some electrical knowledge.
Without knowing the specific type of compressor, it's hard to give more precise instructions. Providing more information, like the make and model, would help in further diagnosis.
