Andrews E75 Fault Code: Causes, Fixes & Repair Costs
What does the Andrews E75 fault code mean?
E75 on an Andrews water heater means the return temperature sensor circuit is reading as a short — the control board sees near-zero resistance where the sensor should be, which corresponds to an impossible temperature reading. It is the mirror image of E65 (the same sensor gone open circuit). A shorted return sensor deprives the controls of a trustworthy return-water temperature, so the unit stops normal operation and holds the code until the circuit is repaired. The cause is almost always the sensor element itself failing shorted, or its wiring being crushed, pinched or wet so the conductors touch.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Shorted return sensor (NTC) Common
The thermistor element can fail short after years of thermal cycling. The board reads near-zero resistance — off the top of the temperature table — and raises E75. A replacement sensor resolves it.
- Damaged or wet wiring shorting the circuit Sometimes
A pinched loom, chafed insulation against the casing, or moisture in a connector can bridge the sensor conductors. The signature is identical to a shorted sensor, which is why engineers test at both ends of the lead.
- Control board input fault Rare
Rarely the PCB's measuring input fails in a way that reads as a permanent short even with the sensor disconnected. Measuring at the board connector with the loom unplugged identifies this case.
How to fix it
- Record the code and context DIY safe
Note whether E75 appeared suddenly in normal service or after work on the unit — recent disturbance points to wiring, spontaneous appearance points to the sensor.
- Try one reset DIY safe
A single reset establishes whether the short is constant. A hard short brings E75 straight back; leave it at that and book service.
- Do not investigate the wiring yourself Gas Safe engineer
The sensor loom runs inside a commercial gas appliance with mains-voltage controls. Diagnosis belongs to a Gas Safe registered engineer with commercial qualifications.
- Engineer: test sensor, loom and board, then replace the failed element Gas Safe engineer
Resistance checks at the sensor and at the board connector isolate whether the sensor, the loom or the PCB input is shorted. The usual fix is a new return sensor or a wiring repair; the engineer should confirm sensible flow/return readings before handing back.
Parts you may need
- Return temperature sensor (NTC) · from £35
- Sensor wiring loom · from £40
- Main control PCB · from £320
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£320, depending on the underlying cause.
Frequently asked questions
What does E75 mean on an Andrews MAXXflo?
The return temperature sensor circuit is reading as a short circuit — an impossibly low resistance — so the controls cannot trust the return-water temperature and stop the unit. It is the counterpart of E65, which is the same circuit gone open.
Will a reset clear E75?
Only if the short was momentary, which is uncommon. A genuinely shorted sensor or crushed lead brings the code straight back. One reset to confirm is fine; after that it needs an engineer, not repetition.
How expensive is an E75 repair?
Usually modest: the sensor itself is a cheap part and access is straightforward, so most repairs land toward the lower end of £120–£320 including a commercial engineer's attendance. A wiring repair is similar; only a control board failure pushes toward the top end. Get a written quote — commercial rates vary.