I’m not sure if I posted this twice as I posted, it displayed and after a refresh was gone.
I insert the tester with the engine and car off. It registers 12.87v. I then started the engine fully and it drops to 7.25v. Once started it then jumped back up. I didn’t turn the car off, so that’s with it on from the drop onwards. As far as I know that means the fuel pump started running from the point where it turned on (ie after the 7.25v was registered).
I did a few tests the worst was 6.5v, issues are the vehicle stalls when start stop is turned on at junctions eg traffic lights and it states “start stop is unavailable.”
I have some other intermittent messages eg “check glow plugs” which is not always showing but just some of the time. I have suspected a poor battery for a while, around 1.5 years ago I called breakdown as when I tried to start the car it wouldn’t and the lights / battery was showing. I eventually got it going by disabling the AC, removing dash cam, turning all lights off, setting the radio to not turn on at start up and tried it a few times.
This has happened once or twice since, but 99.9999% of the time it starts perfectly first time so I was a little dubious as to whether it was a battery issue. It’s nice to finally have this graph and be able to say it seems like a problem, Halfords had a look and said my car wasn’t reporting any data and told me to go Fiat, which I had been avoiding as I suspect the diagnostic charges were high.