I've had a search and can't find any similar topics so hopefully this hasn't been asked yet.
We have an '07 S-Max, the temp gauge never goes above 30 (about 1/4 mark) and the car heating takes for ever to get luke warm.
On a recent 300 mile journey the temp gauge never went over 30 and then dropped down to zero mid journey, at which point the heaters went cold, despite being on max. It was last weekend through the midlands so cold and snowy. After about 10 minutes the temp rose back up to 30 again.
Are there any diagnostics I can run. I don't believe the issue is with the gauge as the dial moves to 30, so I suspect a temp sensor but are unsure where to start.