Average MPG randomly resetting

[bezzawezza]

Hi all

have a weird thing happening with the wife's 13 late Fiesta. Randomly every few days when you start the car the electrics will stutter and the average mpg will reset itself.

it started in January but we noticed at that time the battery was low so we changed that and the problem seemed to go away. 6 months later though it's back and this time the battery appears to be fine (cigarette lighter battery tester reads 12v at rest and 13.5 -14v when running the car).

Does anyone have any idea as to what could be resetting this intermittently?

[Bobr]

It should read more than 12 volts if it's fully charged.   Should be at least 12.5 volts.

[winemart2]

Mine reads ~14.5V

http://www.ebay.co.uk/itm/Digital-LED-Auto-Car-Cigarette-Lighter-Volt-Voltage-Measurement-Meter-12V-24V-/222544360137?hash=item33d0ad72c9:g:aCIAAOSw1BlZP4-k

 

[Tdci-Peter]

16 hours ago, bezzawezza said:

Randomly every few days when you start the car the electrics will stutter and the average mpg will reset itself.

Bad earth connection between battery and engine? The fat wire from the battery -ve to the engine, usually to a bell housing bolt near the starter. Check both ends are tight, not badly corroded, and the wire is not weak & floppy near the crimped ends. Wire breaks inside the insulation are possible.

[bezzawezza]

23 hours ago, Bobr said:

It should read more than 12 volts if it's fully charged.   Should be at least 12.5 volts.

I think the cigarette lighter battery checker that I'm using under-reads in honesty and I only ever use it as a rough guide. Consequently I don't think the battery is low quite yet.

[bezzawezza]

11 hours ago, winemart2 said:

Mine reads ~14.5V

http://www.ebay.co.uk/itm/Digital-LED-Auto-Car-Cigarette-Lighter-Volt-Voltage-Measurement-Meter-12V-24V-/222544360137?hash=item33d0ad72c9:g:aCIAAOSw1BlZP4-k

 

That's the same tester I'm using. 14.5 without the car started seems very high though. Are you sure that's correct? As I understand it, when running the car the meter can be anywhere between 13v and 15v depending on the alternator and how you are driving the car.

[bezzawezza]

10 hours ago, Tdci-Peter said:

Bad earth connection between battery and engine? The fat wire from the battery -ve to the engine, usually to a bell housing bolt near the starter. Check both ends are tight, not badly corroded, and the wire is not weak & floppy near the crimped ends. Wire breaks inside the insulation are possible.

I was thinking it could be an earth connection or a fuse tbh but I'm not sure where to start as I understand there are a number of earth points around the car. I'll check this one out as a priority on the weekend though.

[Steven1212]

Did you find out what was wrong with it? Mines doing this too. All the rev dials and petrol dials stutter and when starting the car then the mpg re sets. 

[unofix]

1 hour ago, Steven1212 said:

Did you find out what was wrong with it?

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