Ongoing Fiesta 1l Ecoboost battery issues

[ecoboost4]

The first warning signs were that the car starting locking itself after about a minute if I left it unlocked. Next the radio/clock and driver side window switch went dead (interestingly the passenger side switch still works - is this a separate fuse issue?). I tried charging the battery with a cheap Ring 4A charger and it seemed to only give temporary relief with regard to the locking issue then after about a week the battery would be low again. So I had the 10 year old original Varta EFB battery replaced with a Yuasa equivalent and reset the BMS and thought that might do the trick - wrong. It didn't fix the dead clock/radio/window and now the locking issue is back. There have been no warning lights that I've noticed so far.

So the big question is have I got unlucky with the new battery or is the alternator the issue? What can I do to work out which one it is?

Anyone else had similar issues? Massive thanks in advance if anyone can help!

[Eric Bloodaxe]

Lots of threads on here on battery related issues. Did you ensure the new battery was fully charged when fitted?

You don't mention your pattern of use - do you drive regularly a reasonable distance, or just occasionally and/or short journeys? If the latter, regular charging may be required**.

If you have a multimeter, check the battery voltage at rest (engine off) and while the engine is running. If the latter is in the range approx 13.8 - 14.8v the alternator is probably ok. For voltage engine off, see table below.

**You should be using a modern smart charger such as the Maypole: MayPole battery charger...

(Other brands recommended by members are Noco Genius 5 or C-tek MXS 5 - a few more features but much more expensive).

[TomsFocus]

The car will lock itself after a minute if you don't open a door.  That's a safety feature known as auto-relock.

Have you checked or replaced any of the fuses?  I'm not convinced this one is a battery issue, which would make a change on here lol.

[Eric Bloodaxe]

1 hour ago, TomsFocus said:

I'm not convinced this one is a battery issue, which would make a change on here lol.

Certainly would! Yes, the window switch working one side is suspicious, still, if all the battery related  stuff checks out ok, then at least that's out of the way.

[ecoboost4]

7 hours ago, Eric Bloodaxe said:

Lots of threads on here on battery related issues. Did you ensure the new battery was fully charged when fitted?

You don't mention your pattern of use - do you drive regularly a reasonable distance, or just occasionally and/or short journeys? If the latter, regular charging may be required**.

If you have a multimeter, check the battery voltage at rest (engine off) and while the engine is running. If the latter is in the range approx 13.8 - 14.8v the alternator is probably ok. For voltage engine off, see table below.

**You should be using a modern smart charger such as the Maypole: MayPole battery charger...

(Other brands recommended by members are Noco Genius 5 or C-tek MXS 5 - a few more features but much more expensive).

It's a ring smart charger, so obviously at the cheaper end compared to a Ctek. It gives a reading of about 12.6v when the issue is happening and the car is off and then appears to charge up to about 14.6v (which I find weird since 12.6v is supposed to be the max when it's off and 14.8v when the car is on). I'll have to buy a multimeter to get an accurate reading.

With regard to driving distances and frequency it's not great, shorter journeys about 10-15 minutes each way a couple of times a week with the occasional 30-45 min drive as well. The original battery lasted years doing that without any issues/symptoms and I've already charged this new battery twice within the space of a couple of months.

[ecoboost4]

6 hours ago, TomsFocus said:

The car will lock itself after a minute if you don't open a door.  That's a safety feature known as auto-relock.

Have you checked or replaced any of the fuses?  I'm not convinced this one is a battery issue, which would make a change on here lol.

I know about the relock if you don't open a door in time, this happens randomly sometimes when I'm sitting in the car and I haven't turned it on yet. Haven't checked the fuses yet but am wondering if there's 2 issues at once and the clock/radio/windows are separate to the locking/low battery.

Could a low battery on the old battery blow the fuses?

[unofix]

3 minutes ago, ecoboost4 said:

about 14.6v (which I find weird since 12.6v is supposed to be the max when it's off

Table shows 12.60V +

Are you waiting 1 hour after switching off the engine before measuring the 'at rest' voltage ?

[unofix]

2 minutes ago, ecoboost4 said:

Could a low battery on the old battery blow the fuses?

The state of charge of a battery, new, old or other can not blow a fuse.

A fuse can only in all cases only be blown by the load (device) drawing excess current.

[ecoboost4]

2 minutes ago, unofix said:

Table shows 12.60V +

Are you waiting 1 hour after switching off the engine before measuring the 'at rest' voltage ?

Yep, sometimes the car hasn't been driven for days.

[TomsFocus]

10 hours ago, ecoboost4 said:

I know about the relock if you don't open a door in time, this happens randomly sometimes when I'm sitting in the car and I haven't turned it on yet. Haven't checked the fuses yet but am wondering if there's 2 issues at once and the clock/radio/windows are separate to the locking/low battery.

Could a low battery on the old battery blow the fuses?

I'm wondering if the car knows you've opened the door.  If it doesn't, then it will auto-relock.  (I had a previous car that locked the keys inside because of this!)

I reckon the door module is faulty, or there are broken wires in the door loom.

Does the radio work when you start the engine, or just not at all now?

[ecoboost4]

On 9/2/2024 at 9:13 AM, TomsFocus said:

I'm wondering if the car knows you've opened the door.  If it doesn't, then it will auto-relock.  (I had a previous car that locked the keys inside because of this!)

I reckon the door module is faulty, or there are broken wires in the door loom.

Does the radio work when you start the engine, or just not at all now?

Nope, radio is completely dead at all times. The door will sometimes stay unlocked for multiple minutes if I'm loading/unloading the car and not lock so I assume that points more towards battery saving behaviour. At other times it'll lock itself with the driver door open!

How would I check the door module? Is there a fuse involved?

[TomsFocus]

If you've opened other doors to load or unload then that overrides the auto relock.

It will relock with the drivers door open if it doesn't know the door is open.

Radio probably is a fuse.  Do you have a handbook for the car?  The fuses are in there.

Door modules are individually fused on some models though I'd have to check the fuse list on the Mk7 as can't remember.

[TomsFocus]

F38 under bonnet - drivers door module (RHD)

F15 & F21 under glovebox - audio unit

 

[ecoboost4]

On 9/4/2024 at 7:48 PM, TomsFocus said:

F38 under bonnet - drivers door module (RHD)

F15 & F21 under glovebox - audio unit

 

Thanks, checking back in to update:

I checked glovebox fuses 15, 21, 23, 26, 27, 28, 43 and bonnet fuses 9 and 38. (I've got a heated windshield issue as well that I noticed ages ago). Only 23 was blown so that will probably sort the radio/clock. The bonnet fuse 9 was a weird cube shape with solid metal rather than a wire but nothing looked obviously wrong, there is a relay R2 that is also linked to the windshield but unsure how to tell if a relay is dodgy. 

You may be onto something with regard to the car not recognizing the door though as opening the passenger door instead of the driver's will stop the car locking itself. Left it unlocked the whole time I was fiddling with the fuses and no self-lock at all. The problem is the fuse looked fine!

[TomsFocus]

Does the whole windscreen not work or just half of it?

The screen won't work with low battery charge, so that may be the cause if the whole screen doesn't work.

[ecoboost4]

On 9/15/2024 at 7:37 PM, TomsFocus said:

Does the whole windscreen not work or just half of it?

The screen won't work with low battery charge, so that may be the cause if the whole screen doesn't work.

Probably need to wait for it to get a bit colder before I can see. Btw is there any specifications (e.g. max 10 amps) I need to take into account when buying a multimeter for testing the fuses/relay/battery voltage? If the drivers door fuse 9 reads ok I'm going to be pretty stumped though.

Also, would the battery need to be disconnected when checking the fuses/would I have to remove the fuse?

[TomsFocus]

9 minutes ago, ecoboost4 said:

Probably need to wait for it to get a bit colder before I can see. Btw is there any specifications (e.g. max 10 amps) I need to take into account when buying a multimeter for testing the fuses/relay/battery voltage? If the drivers door fuse 9 reads ok I'm going to be pretty stumped though.

Also, would the battery need to be disconnected when checking the fuses/would I have to remove the fuse?

You won't be reading current, so amps doesn't really matter.  But for reference, there are some circuits on the car that are up to 60+ amps. 

There are a few different ways to test fuses.  You can remove the fuse, then do a continuity test across the two pins.  That simply checks whether the two are connected or not using a resistance test.

But to save removing fuses, you can do a voltage test instead.  Leave the fuse in place, switch ignition on, then probe each side of the fuse with the positive probe, while holding the negative to an earth point.  Both sides of the fuse should show the same voltage.  If there is voltage on just one side of the fuse, it has blown.  The ignition barrel is a good earth point inside, but if it's keyless ignition then just find any chassis bolt around the fusebox.  As long as it's in the chassis (not just a piece of plastic trim) it will be earthed.

For engine bay fuses, you can just use the main battery negative.