Battery issue

QI recently purchased a 2013 Fiesta 1.0 Ecoboost 125PS Titanium model, and whilst checking out the car noticed the battery voltage to be 11.8V after being used only the day before. The car started OK and had a charge voltage around 14.2V and no issues. The following day checking the voltage it was 12.7V so I thought all was OK, but kept an eye on it and several times was again below 12V.

I carefully removed the negative lead after approximately 30 minutes of stopping engine, with an ammeter in circuit and noticed 1.2amps was flowing, even though nothing was showing to be on, ie. lights, radio, etc, and doors were locked. When the voltage was down below 12V there was no current flowing. This is not consistent though as checked many times in identical circumstances and sometimes there is no current flowing and battery volts stay up for days.

Looking at forums, some say it is software-related for the Bluetooth radio (Sony) and that it sometimes searches for a Bluetooth device even when apparently off, but checking my phone shows no connection possible? I don’t trust the car if I need to park it up for a while.

I’m at a loss as to where to look next. Alan Barton

AI am first presuming the battery is under three years old and in good condition. If not it may be the case that the battery depletion is due to sulphur having deteriorated the battery plates. This can cause the battery voltage to drop at random intervals and give similar symptoms to a current draw.

As you have used an ammeter to prove that there is a drain on the battery this should not be the case, but the meter does need to be left in place for at least 30-40 minutes to ensure that all the systems have fully shut down before reading off any battery drain. It should also be noted that during this period the doors should not be opened, as this will wake up the body systems and give a false reading.

If this is the case then it is possible that the Sony radio is the cause of the battery depletion and I have come across this before. To confirm this you should remove fuse number 21 in the interior fusebox. This will disable the radio and you can recheck for any battery drain using the ammeter.

Once the source of the drain is confirmed then action can be taken and you may wish to have the unit repaired or replaced with either a second-hand unit or an aftermarket unit. Although given that the audio system is quite integrated, the fitting kit for an alternative audio system is expensive.