Franklin SubDrive 2 Flashes: Short Circuit Fault Guide

The ‘2 Flashes’ fault code on a Franklin Electric SubDrive is the controller’s self-preservation mechanism against a high-amperage short circuit event. From an engineering perspective, the Variable Frequency Drive (VFD) is designed to constantly monitor the current flowing through its Insulated Gate Bipolar Transistors (IGBTs) to the three-phase submersible motor. When insulation on the motor’s power cable is breached—either between phases or from a phase to ground—it creates a low-resistance path. Per Ohm’s Law (I = V/R), as resistance (R) approaches zero, the current (I) spikes to a potentially destructive level. The drive’s logic detects this near-instantaneous surge and trips the output in microseconds to prevent the IGBTs from exploding.

The two most common physical causes for this electrical failure occur downhole. The first is a breakdown of a waterproof splice. A submersible pump installation requires at least one splice between the motor’s short leads and the main drop cable. If this splice was installed with any contamination (dirt, skin oils) or insufficient heat during the heat-shrink process, mineralized well water can eventually ingress. This water creates a conductive path, leading to a short. The second common cause is cable abrasion. Over years of operation, the torque from the motor starting and stopping can cause the power cable to rub against the rough steel well casing. This constant friction wears through the cable’s outer jacket and inner insulation, eventually exposing the copper conductors and causing a direct short against the grounded casing.

While the VFD is designed to protect itself, the underlying fault can still damage the motor. Each short circuit event sends a high-voltage, high-current transient down the line. This can stress the motor’s internal winding insulation, which is a thin enamel coating on the copper wires. Repeated faults can lead to a ‘pinhole’ breakdown in this enamel, causing an internal, non-repairable motor short. Furthermore, a powerful arc from a dead short can superheat the surrounding water, creating a steam pocket and a concussive force. While rare, this pressure wave can stress the motor’s mechanical seals or thrust bearing assembly, although the primary failure is almost always the electrical path itself long before mechanical damage is evident.

• Perform a Full Power Cycle: Shut off the dedicated double-pole breaker for the pump system in your main electrical panel. Leave it off for at least 15 minutes. This allows the drive’s internal capacitors to fully discharge and its microprocessor to reset, clearing any transient software glitches.
• Visual Inspection at Wellhead: Carefully inspect the wiring entering the well cap. Look for any signs of physical damage, rodent chewing on conduits, corrosion on terminals, or evidence of moisture inside the well cap’s junction area. A burnt smell is a definitive sign of a problem.
• Isolate the Motor from the Drive: Turn the power OFF at the breaker. At the SubDrive controller, use an insulated screwdriver to disconnect the three motor output leads (labeled U, V, W) and the ground wire. Ensure the disconnected wires are separated and not touching each other or any metal part of the controller chassis.
• Test the Drive Independently: With the motor leads still disconnected, turn the breaker back ON. If the ‘2 Flashes’ fault code disappears and is replaced by a different code (e.g., ‘Open Circuit’, ‘No Load’, or ‘Dry Well’), you have successfully confirmed the fault exists downstream in the wiring or the motor itself. If the ‘2 Flashes’ fault persists with nothing connected, the drive itself has a failed output stage and requires replacement.
• Basic Multimeter Resistance Check (Power OFF): Ensure power is off. Set your multimeter to the lowest Ohms (Ω) setting. Measure the resistance between the disconnected motor leads: U to V, V to W, and U to W. The readings should be very low (typically 0.5-5 ohms) and, most importantly, nearly identical to each other. A reading of zero indicates a dead short between phases.
• Basic Insulation Check to Ground (Power OFF): Set your multimeter to the highest Ohms (MΩ) setting. Measure the resistance from each motor lead (U, V, and W) to the ground wire. A healthy motor and cable will read ‘O.L.’ or infinite resistance. Any reading, even in the thousands or millions of ohms, suggests an insulation leak and is a likely cause of the fault.

The cost for a professional service call to diagnose and repair a short circuit fault typically ranges from $850 to $2,200 in the United States. This price reflects the specialized nature of the work. The primary cost drivers are labor and equipment mobilization. This is often a two-person job requiring 3 to 5 hours on-site, and the fee includes the dispatch of a service truck equipped with a hydraulic pump hoist or crane, which is a significant operational expense.

The final invoice is influenced by several variables. The well depth is the most significant factor; a 500-foot well requires far more time and labor to pull and reinstall than a 100-foot well. The cost of materials, such as a premium-grade heat-shrink splice kit from a manufacturer like 3M or Franklin Electric, also contributes. If the initial megohmmeter test reveals that the motor windings are internally shorted (a non-repairable condition), the job will escalate from a wire repair to a full pump and motor replacement, which would substantially increase the cost beyond this initial estimate. Emergency or after-hours service will also command a premium rate.