Battery drain

I would be most grateful for advice on a problem with my son-in-law’s 61-plate Ford Mondeo Titanium 1.6 petrol with 60,000 miles. Apart from one problem, the vehicle runs completely normally. There are no error codes.

For the past six months, on leaving the vehicle overnight, there is not sufficient power in the battery to start the engine and it needs to be jump-started. Once started, it runs completely normally and there are no error codes. The battery has been tested and pronounced OK. The charging rate is also fine.

I suspect something is draining the battery. There are reports on the internet about similar problems with this model, so it might be a stock fault. The local Ford main agent has suggested a software upgrade for £80, with the proviso that doing this might generate additional problems. My son-in-law is trying to isolate the problem fuse by fuse, but this could take some time. Is this a sensible thing to do and might the procedure result in further problems? Robert Talbot As you say, this is a common problem and there were about 54 pages of discussion about it on the Talk Ford website.

If the problem with your son-in-law’s car is the same as other Mondeo owners, the fault seems to lie with the audio system. While some people report that the drain only occurs when a USB is left plugged in, others have differing problems. It appears a software update may cure the fault, but this is not guaranteed.

Unlike early vehicles, the complex systems used today make testing for a drain slightly more complicated. Most vehicle systems take around half-anhour to power down, while others take longer. I would advise starting your investigation by removing the audio fuse F6 from the passenger fusebox. If this cures the problem, you at least know the fault is with the audio system; if it makes no difference, further steps need to be taken. You will need to re-enter the radio code when replacing the fuse, but I am assuming this is readily available. From the data I have, your son-in-law’s vehicle will also have a battery monitoring system fitted, which may need resetting after removing the terminals.