Solar Borehole Pump Not Pumping? Common Causes and Fixes

Your solar borehole pump was running fine, and now it isn’t — or it is, but barely. Before you call anyone, it helps to know what you’re actually dealing with. Solar pump faults follow recognisable patterns, and narrowing down the cause saves you both time and call-out fees.

How a Solar Borehole Pump System Actually Works

A solar pump system has four main parts that must all cooperate: the photovoltaic (PV) panels, a solar pump controller (sometimes called a variable frequency drive or VFD), the submersible pump and motor down the borehole, and the rising main and pipework that carries water to the surface. If any link in that chain is weak, flow drops or stops entirely. Understanding this helps you work through a fault systematically rather than guessing.

The Most Common Reasons a Solar Borehole Pump Stops or Underperforms

Insufficient solar irradiance This is the single most frequent complaint. On heavily overcast days, your panels may produce 20–30 % of their rated output. Many solar controllers are programmed with a minimum input voltage — if panels fall below that threshold, the controller simply will not start the pump. This is not a fault; it is by design. If your pump runs fine on sunny days and stops on cloudy ones, the system is probably behaving correctly. The fix may be adding more panels rather than replacing components.

The pump trips at midday Counterintuitively, very high summer temperatures reduce panel efficiency and can also cause the controller to overheat and throttle output. If the pump stops around noon on hot days but restarts later in the afternoon, check whether the controller enclosure has adequate ventilation and is not in direct sun. Controllers are typically rated for specific ambient temperature ranges — check the manufacturer’s data sheet.

Controller or VFD fault codes Most modern solar controllers display fault codes. Common codes relate to under-voltage, over-voltage, dry-run protection (the pump has sensed it is drawing no water and has shut itself off), and motor overload. Do not ignore fault codes or simply reset the controller repeatedly without understanding the underlying cause. A persistent dry-run fault, for example, may indicate the borehole water level has dropped — forcing the pump to run dry will destroy it quickly.

Wiring and connection problems Loose terminals, corroded connectors, and undersized cable are responsible for a significant share of solar pump faults — particularly on systems that have been running for a few years. Voltage drop across a long cable run between panels and controller, or between controller and pump, reduces the power the motor receives. Check all accessible connections for corrosion or looseness. Any work on the electrical connections between panels and controller, or on the submersible cable, should be done by a qualified electrician or solar technician.

Worn pump or motor Submersible pumps have a service life. Impellers wear, bearings fail, and motor windings degrade — especially if the pump has ever run dry or handled water with high sand content. Symptoms include gradually declining flow over months, unusual noise from the borehole (a rattling or grinding sound), or a motor that draws abnormal current. If you suspect pump wear, you will need a technician with a pull rig to retrieve the pump for inspection. This is also a good moment to review the full system with a specialist — our guide to borehole pump faults and what they mean covers the diagnostic steps in detail.

Low borehole water level Drought, over-abstraction, or seasonal aquifer changes can lower the static water level in your borehole. If the pump’s intake rises above the water surface, it runs dry. Responsible systems include a float switch or pressure sensor to prevent this. If yours does not, or if the sensor has failed, dry-running is a real risk. Signs include reduced yield that worsens through the dry season, the dry-run fault code mentioned above, or sediment appearing in the water.

Solar vs Mains Power: Does the Fault Change?

A pump that runs on Eskom power but not on solar is almost always a power-supply issue — panels, controller, or wiring — rather than the pump itself. A pump that fails on both power sources points to the pump or motor. If you are considering switching from solar to a grid-tied backup or vice versa, comparing solar and Eskom-powered borehole pumps is worth reading before you commit to hardware changes.

Low Flow but the Pump Is Running

Low flow with the pump running is a separate problem from no flow at all. Common causes include:

• Partially blocked intake screen — sediment or biofilm can restrict the pump inlet
• Worn impellers — reduced pumping efficiency without complete failure
• Undersized controller output — if the controller is throttling the motor because of low panel voltage, flow will be reduced proportionally
• Pipe or valve restriction — check that all isolating valves above ground are fully open and that the rising main has no obvious damage
• Borehole yield lower than pump demand — the pump may be rated for a higher yield than the borehole can sustain

Our low borehole pressure troubleshooting guide walks through each of these in more detail.

If a technician visit confirms the pump or borehole needs work and you want a second opinion on costs, it's worth comparing what different installers quote. Get 3 free quotes from vetted installers — no obligation, no pressure.

What You Can Check Yourself vs What Needs a Technician

Task	DIY-safe?
Check panel surfaces for dirt, shading, or bird droppings	Yes
Read and note controller fault codes	Yes
Confirm all above-ground valves are open	Yes
Check controller ventilation and enclosure temperature	Yes
Inspect above-ground wiring connections for obvious corrosion	With caution — isolate first
Test panel open-circuit voltage with a multimeter	With caution — follow safety steps
Work on submersible cable or live panel wiring	No — qualified technician
Pull the pump from the borehole	No — specialist with equipment
Measure borehole water level	No — specialist with instruments

A useful rule: anything above ground and unpowered you can usually inspect safely. Anything below ground or involving live DC wiring from the panels needs a professional.

When the Problem Is the Borehole Itself

Not every solar pump fault is a pump or panel problem. If your borehole’s water level has dropped, or if the borehole casing has deteriorated and is allowing surface contamination in, the fix is not electrical. Water quality changes — cloudiness, unusual smell, or taste — alongside pump problems can indicate casing failure or a polluted aquifer. Water from any borehole used for drinking should be tested against SANS 241, South Africa’s drinking-water quality standard, at least annually and after any suspected contamination event.

If your borehole is ageing or you suspect structural issues, a specialist borehole company should camera-inspect the casing before you spend money on pump replacements. You can find out more about what a complete borehole installation involves on our borehole drilling overview page, which also explains what to look for when evaluating a contractor.

Dealing with a borehole problem that's beyond a simple panel clean or controller reset? Compare quotes from three local borehole specialists — vetted, rated, and under no obligation to you.

Preventing Repeat Faults

Most solar borehole pump failures are predictable and avoidable with basic maintenance:

• Clean panels every one to two months in dusty or pollen-heavy areas — dirty glass can cut output substantially
• Check and tighten all above-ground electrical connections annually — thermal cycling loosens terminals over time
• Test your dry-run protection regularly — simulate a low-water condition or confirm the sensor is reading correctly
• Keep a log of daily pump hours and tank fill times — a gradual decline is easy to miss day-to-day but obvious in a simple record
• Service the pump on the manufacturer’s recommended schedule — most submersible pumps benefit from an inspection every three to five years depending on water quality and duty cycle

Solar borehole pumps are reliable systems when they are correctly sized, properly installed, and given basic attention. When they do develop faults, working through the checklist above — panels, controller, wiring, pump condition, borehole yield — usually identifies the problem without unnecessary parts replacement or expensive call-outs.