QD Boxes are designed for use with 3-wire, single phase submersible motors from ½ to 1 HP. Troubleshooting inside the box is made simple by the control components automatically disconnecting from the system when the lid is removed.

Caution! Electricity can be very dangerous, especially if you are inexperienced. Always use caution working with electricity and turn off power supply breakers when testing components within the electrical system. If you are not 100% confident you can perform any of these tests safely, call a professional.

How the QD Box Works

Standard QD boxes contain just a start capacitor and QD relay. The old QD CRC boxes (Capacitor Run Capacitor Start) also contain a run capacitor. The incoming power is attached at L1 and L2. The pump wires connect to R, Y, and B — R (red) is the start winding, Y (yellow) is the common, and B (black) is the run winding.

When the motor starts, both the start and main windings are energized. As the motor approaches running speed, the start capacitor and start winding must be disconnected, and the motor operates on the run winding alone. The QD relay handles this disconnect. In the QD CRC Box, the start winding and run capacitor(s) stay connected even at running speed.

Step-by-Step: Testing Your QD Control Box

Step 1: Check the Capacitor(s)

Using an ohmmeter set to R X 1,000, place your leads on either of the capacitor terminals. The meter should swing toward zero, then back to infinity. Note: a capacitor that has lost some capacitance may test okay but no longer function properly.

Step 2: Check the QD Relay (Triac Test)

Using an ohmmeter set to R X 1,000, connect meter leads to the capacitor and B terminals. You should get an infinity reading.

Step 3: Coil Test

Using an ohmmeter set to R X 1, connect meter leads to L1 and B. The correct reading is Zero ohms for all models.

Step 4: Measure Voltage (Power Must Be On)

Warning: Do not touch any live parts. Contact a professional if you are not comfortable working with hot wires.

With the motor off, measure voltage at L1 and L2 of the pressure switch or line contactor. The reading should be +/- 10% of motor rating. With the motor running, measure voltage at the load side — it should remain the same except for a slight dip on starting. Excessive voltage drop can be caused by loose connections, bad contacts, ground faults, or inadequate power supply. Relay chatter is caused by low voltage or ground faults.

Shop Franklin Electric QD Control Boxes

If your testing reveals a failed QD box, we carry the full Franklin Electric lineup for 3-wire submersible motors:

• Franklin Electric QD Control Boxes — quick-disconnect design for easy installation and service
• Franklin Electric Standard Control Boxes — reliable for 1–15 HP 3-wire motors
• Franklin Electric CRC Control Boxes — corrosion-resistant for demanding environments
• Franklin Electric Deluxe Control Box 230V 1PH — built-in line contactor, no external contactor needed

Related Guides

• 📖 How to Troubleshoot Franklin Electric Control Boxes (1.5–15 HP)
• 📖 Troubleshooting Submersible Well Pumps 101 — Overloads Tripping
• 📖 Troubleshooting Submersible Well Pumps 101 — Pump Does Not Start
• 📖 Troubleshooting 4" Submersible Motor: Insulation & Windings Resistance

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