Debugging stale readings

Trace stale or missing probe readings from firmware through relay cache to ProbeHarbor dashboard mapping, with a curl and auth checklist.

Close-up of white Cat-5e Ethernet cables with RJ45 connectors
Probe JSON usually leaves the LAN over Ethernet or a nearby relay, not the public internet directly. Photo: DiscDepotDundee.co.uk. CC BY-SA 4.0

Stale readings mean the website shows an old temperature while the space has moved on, or shows nothing while the LCD still updates. Work from the sensor outward: hardware, JSON, cache, SSR fetch, then history.

Checklist

  1. curl the feed URL from outside your LAN: is JSON fresh?
  2. Compare LCD vs JSON, if LCD wins, fix relay or Redis TTL.
  3. Verify probe keys in dashboard match schema: probe mapping.
  4. Inspect Cloudflare / SSR logs for timeout patterns.

Hardware-side causes

Watchdog reboots cause short gaps. DHT22 errors drop keys from JSON. Ethernet: wiring troubleshooting.

History vs live

Charts can lag if inserts stop but home page still looks live: check history inserts separately from home page fetch.

FAQ

Why are my probe readings stale?
Check device power and Wi‑Fi, verify the ingest key, confirm cron/history jobs on System status, and look for gaps in History before replacing sensors.