- Heat pumps
- Pool heat pump
ER03
Poolex Er 03 on pool heat pump: flow sensor malfunction
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
On the Poolex Jetline Selection Fi, code 03 means a flow sensor malfunction: it does not detect enough water in the heat exchanger. Check that the filtration is running and that the by-pass valves are set correctly.
Safety first
Stop and check this first
- Do not bridge or block the flow sensor to make the unit start: it is the protection that stops it running with no water in the heat exchanger.
- Poolex requires the power supply to be disconnected before any work or maintenance on the heat pump. Do not open the casing: water and mains voltage are together inside.
Safe checks you can perform
- Filter pump running and water in the pool
- By-pass valves
- Clean pool filter
- Status values and fault history
Leave these tasks to a qualified professional
- Do not attempt this professional task: Measuring the real flow
- Do not attempt this professional task: Flow sensor connection and test
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Measuring the real flow
What they doThe technician measures the flow through the heat pump and compares it with the minimum and maximum flow for your model in the manual's specification table.
They must show youthe measured flow against the minimum and maximum for your model.
In writingthe measured flow, the by-pass valve positions and the adjustment made.
Flow sensor connection and test
What they doWith the power off, the technician checks the flow sensor connector and confirms it changes state when water flows, as the Poolex table asks (reconnect or replace).
They must show youa photo of the connector and the sensor test result with water flowing.
In writingwhether the sensor was reconnected or replaced, the part reference and the reason.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Filter pump running and water in the pool
- Who:
- you, without tools.
- How:
- confirm the filter pump is running, the pool water level is normal and water returns to the pool; if the circulating pump is wired to terminals P1 and P2, the heat pump starts it itself. Poolex says never to start the unit with no water in the pool or with the circulating pump stopped.
- Result that matters:
- water flowing through the heat pump while it is on.
- If the filtration was stopped or paused by its timer:
- start it and see whether the code clears.
- If the filtration runs normally:
- move on to the by-pass valves.
- Evidence to keep:
- the filtration timer setting and a photo of the water return.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
By-pass valves
- Who:
- you, without tools.
- How:
- the by-pass is 3 valves that regulate the water going through the heat pump. Compare their position with the diagram in section 3.6 of the manual, which marks which valves are open and which one is half open, and correct any that does not match.
- Result that matters:
- inlet and outlet valves open and the by-pass valve set as the diagram shows.
- If one was closed or badly set:
- correct it and see whether the code clears.
- If they match the diagram:
- check the filter.
- Evidence to keep:
- a photo of the 3 valves before and after touching anything.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Clean pool filter
- Who:
- you, with the filtration stopped as your filter's instructions say.
- How:
- clean or backwash the filter upstream of the heat pump. Poolex asks you to check the water flow every month and clean the filter if needed, because a dirty filter causes operating problems.
- Result that matters:
- a stronger return flow with a clean filter.
- If the filter was dirty and the code does not come back:
- the cause was low flow.
- If the filter was clean or the code comes back:
- call a technician.
- Evidence to keep:
- the cleaning date and a photo of the filter.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Status values and fault history
- Who:
- you, from the heat pump controller.
- How:
- enter status check mode by holding for 3 seconds the button shown in section 5.9 of the manual; step through the parameters and note the water pump state (Pu) and codes HE1 to HE4 (fault history).
- Result that matters:
- knowing whether the code repeats in the history and which values the unit showed.
- If the history shows the same code several times:
- it is not a one off; show it to the technician.
- If it is the first time and it clears once the water is corrected:
- watch it for a few days before calling.
- Evidence to keep:
- a photo of each value on the screen, with the date.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Heat pumps
- Brand
- Poolex
- Product type
- Pool heat pump
Known code variants
- bomba de calor Zodiac sin caudal
- E03
- Er 03
- Poolex 03
- Poolex E03
- Poolex error 03
- Poolex fallo sensor de caudal
- Poolex flow sensor fault
- Poolex Jetline Selection Fi 03
- Zodiac Er03
- Zodiac heat pump lack of water flow
- Zodiac Z250 Er03
- Zodiac Z250 falta de caudal de agua
- Zodiac Z250 no water flow
What it means
In the Jetline Selection Fi fault table, Poolex links code 03 to the water flow switch, which confirms water is passing through the heat exchanger. The manual gives two causes: insufficient water in the heat exchanger, fixed by checking the water circuit and the by-pass valves, or a sensor that is disconnected or defective. A 03 does not prove the sensor is broken: if the filtration is stopped, the filter dirty or the by-pass badly set, the sensor is doing its job.
Warnings and stop conditions
- Mediumeditorial warning
Do not bridge or block the flow sensor to make the unit start: it is the protection that stops it running with no water in the heat exchanger.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
- Highsource verified
Poolex requires the power supply to be disconnected before any work or maintenance on the heat pump. Do not open the casing: water and mains voltage are together inside.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Symptoms and causes
Probable causes · in order
- Too little water in the heat exchangerCommon
The filtration is stopped, the filter dirty or the by-pass valves badly set. It clears once circulation is restored, without touching the unit.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
- Flow sensor disconnectedPossible
Circulation is good but the 03 stays: the sensor connector may be loose. It can only be seen with the casing open and the power off.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
- Defective flow sensorPossible
With correct flow and a sound connection, the sensor does not change state. Poolex says to replace it; a technician confirms it by testing.
Evidence: Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Virtual technician
Does ER03 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Poolex Jetline Selection Fi: installation and user manual (multilingual, 08-2025)
Poolstar (Poolex) · 2025 · official_doc
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