Quick answer
A solar geyser that has stopped heating is usually a circulation pump failure, a degraded or empty glycol loop, a faulty controller sensor, or shaded and dirty panels. Start with what you can see: panel cleanliness, shading from a tree that has grown, and any fault code on the controller. If the backup element has also been disabled to save power during load shedding, you can be left with no heat at all from either source.
Common causes
- Circulation pump failed or air-locked in the closed loop
- Glycol degraded or below level, so heat is never carried from panel to cylinder
- Controller temperature sensor faulty, leaving the pump idle even in full sun
- Panels shaded by growth, or coated in Highveld dust after a dry winter
- Backup element switched off or disabled during a load-shedding routine and never restored
- Vacuum tubes cracked or clouded, common after a hail event
What you can do now
- 1Inspect the panels for shading, dust and any cracked tubes
- 2Check the controller display for a fault code and photograph it before it clears
- 3Confirm the backup element breaker is on at the DB board
- 4Feel the flow and return pipes on a sunny afternoon — both cold means the pump is not circulating
- 5Note the time of day the system does and does not perform; it narrows a sensor fault quickly
When to call a professional
Book a solar service covering a pump test, glycol level and condition check, sensor verification and a panel clean. Call sooner after hail, since cracked tubes let the loop lose pressure and the pump will run dry. Ask for the glycol condition to be reported — degraded glycol turns acidic and quietly corrodes the collector from the inside.
Typical cost in Johannesburg
Service R1,200–R2,400 · Pump replacement R1,800–R3,200
Indicative ranges only. We provide written, itemised quotes before any work.
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