Peugeot 406 Outside Temperature Sensor Fault

Sounds familiar. I had almost the same set of symptoms on my old Opel Astra a few years back. Air con refusing to kick in was the giveaway, along with some odd readings on the dashboard. In my case, it turned out to be a corroded connection at the sensor plug. Have you checked for any signs of corrosion or damage to the wiring near the plug itself? Even a tiny bit of green gunk can cause all sorts of problems.

Thanks for the tip! I’ll definitely take a closer look at the plug and wiring. When you say 'corroded connection', are we talking about cleaning the contacts or replacing the whole plug?

In my case, cleaning didn't do the trick. The corrosion had gotten pretty bad, and the wires were starting to fall apart. Ended up replacing the plug and a short section of wiring. Honestly, though, I'd recommend getting it checked out by a workshop if you're not comfortable doing electrical repairs yourself. It's a small issue, but it can cause bigger problems if not addressed properly.

Thanks again for the advice. I took it to the workshop, and you were spot on! It was a defective cable/plug connection for the sensor, just like you said. They replaced it, and everything is working perfectly now. Total cost was 95€, which isn't too bad. Really appreciate the help!