S.590 on a Vaillant aroTHERM plus: Fault: 4-port valve position not correct The 4-port diverter valve does not move fully to the heating or cooling position
Short answer
On a Vaillant heat pump, S.590 means: Fault: 4-port valve position not correct The 4-port diverter valve does not move fully to the heating or cooling position. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Fault: 4-port valve position not correct The 4-port diverter valve does not move fully to the heating or cooling position.
Part involved: Heat pump control (status/Live Monitor).
When it shows: Fault: 4-port valve position not correct The 4-port diverter valve does not move fully to the heating or cooling position.
Likely causes:
- Fault: 4-port valve position not correct The 4-port diverter valve does not move fully to the heating or cooling position.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Warning |
The heat pump keeps running with some functions stopped.
Resetting itself: yes - status changes automatically with operating state.
Manual reset: not applicable.
What you can check
- Note the status code (Live Monitor). The heat pump will normally retry automatically; if a related F-code appears or heating/hot water stops, contact your installer.
What the engineer will check
- Read Live Monitor status and fault history; if the status persists or precedes an F-code, follow the corresponding F-code diagnostics in the installer fault table.
Who to ask for: Vaillant-trained heat pump installer/engineer (MCS-certified installer).
Certification: MCS installer certification; Vaillant product training recommended.
What you might notice
What owners and engineers report
8 owner and engineer reports mention this.
- Keeps stopping / cutting out on the aroTHERM plus (VWL ../6 A): 6 reports
- Intermittent fault on the aroTHERM plus (VWL ../6 A): 2 reports
Sources
- Heat pump control interface module (VWZ AI) operating and installation instructions ↗ · 0020291573_01 · page VWZ AI appliance interface 0020291573_01 p.33; uniTOWER VIH QW 190/6 E 0020291525_05 p.58; VWZ MEH 97/6 hydraulic station 0020291544_03 p.51; aroTHERM split hydraulic station VWL ../5 IS 0020257319_05 p.56 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026