I took the sensor off the AP903 in the garage and connected it to a (wired) AP903 in a bedroom at about 14.00 yesterday. At around 20.25, 21.30 and 05.25 the graph shows temperature spikes to 198C.

So it's not that particular AP903....

Piste Basher wrote:
So it's not that particular AP903....

Nor the local environment either - unless you have a bedside welder

I've been re-reading the LM75 datasheet and can't for the life of me imagine a fault that would result in those numbers appearing. Maybe it doesn't like being placed next to a couple of radio transmitters - try turning the Wifi off :lol:

An excellent suggestion. But I think I'll await the next firmware update

I re-connected the sensor to the Garage AP903 at about 15.30 yesterday. In the subsequent 2 hours there were two spikes to 199C, but in the following 24 hrs approx. there have been none.

I give up trying to understand what's going on.

Piste Basher wrote:
But I think I'll await the next firmware update

I've got a feeling that the issue lies within the microcontroller in the device, rather than the AP903.

I wonder what it does in the Vigor 2862? ... I assume it's the same temperature sensor.

Have you tried plugging it into a PC? ... It might appear as COM port and dump its raw data in human-readable form (using e.g. Putty )

I've just plugged it into my old 2925. Shall monitor over next 24 hours.

I have a Draytek USB temperature sensor on my AP903 and never observed any spikes at all.
Just a thought since you said that the temperature was a couple of degree's off and that it can be compensated for, If you are compensating then it would be worth switching the compensator off for a few days and see if the problem goes away?

Neil..