997.2 GT3 Temp failure indicator

[Mark A S]

I wonder if anyone here can help

997.2 GT3 today on a “planned” long trip out, got 3 miles or so, and Temp gauge went to 0 with red light on in top right corner. Temp failure indicator warning appeared. Stopped the car, re started still there, drove back home.
Had a good look around, no leaks, water level normal, water pipes in engine bay not too hot to touch nothing obvious untoward.
Plugged in OBD, quite a few fault codes, some not relevant to the GT3, makes me think battery not in great shape? albeit it starts no problem.
Cleared fault on temp sensor, re started car, gauge working, light out.

Set off again, this time got around 10 miles, noticed that at speed water temp dropped below 60 and oil temp around 50, where they normally sit around 80 and 90 all day long summer or winter. Same thing happened temp gauge to zero light on etc, so turn around slow drive home also noticing no warm air out of heater when set at 22, outside temp was 8. Car feels fine, engine runs perfect.

Another check over engine not hot, no signs of leaks, water level full etc. Cleared fault again, started up and left ticking over. After a while water temp up to 80, oil 60/70 fans working on/off, and turning the heater up warm air fills the cabin.

Went for a 10-mile drive 8 on a dual carriageway so up to speed, Car performs as expected. After a mile, at speed water temp dropped to just below 70, oil around 60/70, temps varied a little due to speed etc, but no warning light temp gauge to 0 etc
As mentioned, the temps are normally VERY consistent, so I am a bit perplexed. Could it be a sticky thermostat? I have my battery on a C-tek now as after the run it was only on 3 lights, 40 mins later its on 4. Could the battery be on its way out? Could that cause these weird symptoms?

Thanks in advance.

[NDA]

Odd. It could be the battery - how old is it?

My C4S has just thrown a cooling fault - it's likely to be the changeover valve, although it could be a number of things.

Have you checked your coolant level (when the car's cold of course)?

Slightly flakey batteries play havoc with warnings - but who knows?

[Popolou]

Electrical? Perhaps the alternator is failing under load. If your diagnostic tool allows you to view live data, you may be able to see something not right when driven.

[Mark A S]

Not sure how old the battery is, just started it, starter after a hour or so on the C-tek deffo spun over quicker, battery read 14.7 when running so alternator good. 12.7 just after turning off. Back on charge now.
Up to 80 water, and 70 oil after 10 mins, all seems normal but not been out again.

I have a Temp sensor coming as wiser people than me suggest try that first, fingers crossed!