Technical Help - Alternator Dead or Battery Issue

[markunovica7]

Start Stop Fiat Punto Evo 1.2 Mylife. Started two days ago -I turned it on - first lots of errors - Empty battery was suspected so I left it running for a short time to recharge - measure voltage 13.4v on battery - engine NOT running, but 16-18 Volts with Engine Running. Many dashboard symbols as well as Battery symbol. But as soon as I revved up the engine, all lights disappeared except the Seat belt Warning light. I turned it off and left it overnight to get the service - The next morning the battery is completely dead. Not even remote key unlock - Battery shows 8 volts currently - no life on the car -

 

[bugsymike]

Have battery tested first, but for it to drop that much overnight either you have a massive drain on the system (lights etc) or a duff battery most likely.
As you will know from reading Forum threads if you have stop /start system then a special battery to suit it is required and you may need to read up about the process. Earth leads and wiring corrosion can be another issue, but to me if it loses charge overnight without turning the starter etc. then test battery first.

 

[AndyRKett]

Alternator is likely to have issues if it is putting out 16-18 volts. There should never be a voltage that high.

if the regulator on the alternator is bad, then it could also be the cause of the drain.

The second issue is the 8volts when left, the drain on the battery could have killed the battery as well. a 12v Lead acid battery is not designed to cycle between 18V and 8V and if it has been doing that for a while, maybe not to such an extreme but getting worse over time, its quite possible both need to be replaced. Just get it fixed before the high voltage ruins the electronics of the car.