Hi,

 

I’m hoping someone will be able to assist me in the right direction for getting this issue fixed.

 

The car in question is a 2011 Ford Fiesta Zetec, 1.25L.

 

About 2 months ago my battery light came on when the car was sat stationery in a car park & to begin with it would come on every couple of days. Over time it has gradually come on more and more regularly to the point where it now comes on almost every time I drive the car. I do a LOT of miles in this car and am weekly driving 400 miles up and down the motorway, but when the battery light comes on I seemingly have no issue with driving the car and it has never died on me whilst driving. I always know when the light has come on as the engine dips, before the revs sit a lot higher than normal and it normally comes on after being stationary.
 

2 weeks ago I went to a drive-in cinema and sat with the engine on (battery light on) and after about 1 hour of being sat stationery the car died. I jump-started it and once I was driving again I didn’t have any issues.

 

1 week ago I started the car on the driveway in the morning and after about 5 seconds it died. I tried again with my foot flat on the accelerator and it started successfully and once again after driving off I seemingly did not have any issues.

I would love to get this fixed as I really don’t want to break-down on the motorway (or anywhere for that matter) but if anyone has any guidance as to what this issue could specifically be so that I don’t need a diagnostic that would be great!

 

Many Thanks :)

Sounds like your alternator is not charging. 

Does belt look like it’s turning the alternator properly. Are all wiring connectors on alternator on properly and in good order and not corroded etc. Checking with voltmeter at tickover and revving using heavy loads eg lights quickclear windscreen etc might reveal low output from alternator. Most likely needs new alternator but not certain.

Sounds like typical symptoms of a failing alternator. One day it will just die on you and not restart.

I'd perhaps check the battery voltage before starting (should be around 12.5v), then again once you've started the engine and let it idle for a minute with as many electronics powered on as you can. (around 14-14.4v). You may find you're right on the lower limit so won't affect the running of the car unless you use the stuff that requires a lot of juice (the heated screens, radio, AC, etc.).

My 2012 Focus presents the same problem and failed the other day after about 20 minutes of driving with the red battery light on - it usually goes off and I am fine - this time it did not - I was trying to get home and I did but only in first gear at 10 mph for the last mile, as it is automatic and would not change up, I don't think I had hazard lights either although the indicators were clicking in the car as cars following were confused.  When I got home the battery was flat, but we charged it and the car recovered including it's brain and gear functions.  We examined the battery and alternator but both appear to be fine, we called the AA and he put his diagnostic computer on it and he could find no fault.  Took it to the garage following day they looked and found nothing wrong and refuse to replace the alternator as they said it might not solve the problem and it would be £300 spent unnecessarily.  So battery is fine and alternator fine - anyone with any other ideas please?  I am afraid to drive it now as I do not want to get stuck on a smart motorway or anywhere I can't safely pull off the road, especially if the hazard lights wont work.

 

If the battery is fine and alternator is fine, I wonder if there is a drain somewhere.  Like a relay or some other electronic item is draining current. 

Fair play to the garage for not replacing the alternator.  A mechanic with a conscience is nice to see. Clearly someone who thrives on reputation. 

Battery drain doesn't cause the battery light to come on.

The battery light means the alternator isn't putting out enough voltage and you are running on battery power.

If it's not the alternator it could be the wiring, preventing the smart charge working, or on this year of car, I think the BCM controls the charge, but someone will be along to confirm I'm sure.

It doesn't sound like your mechanic has said the alternator is fine, just that it MIGHT not be that.

What is the voltage when the engine is running? They usually have a default safe voltage the alternator operates at if it can't get a comms signal.

The alternator should be able to produce far more current than any battery drain could take with the engine running.  If the alternator genuinely is fine, I'd say it's output is being restricted by the PCM for some reason.

The Mk3's have variable rate charging as well as SmartCharge.  So it's a possibility that the PCM thinks the battery charge is higher than it actually is.  In the short term, you can unplug the SmartCharge plug which should default the voltage output to 13.5v.  Not great long term, but should at least get you home if necessary in future.

I assume the thick battery cables and terminals have all been checked?

I have the same problem with the light coming on. Voltage when driving is anywhere between 11v and 14.8v.  when light is on voltage seems to stay at about 13.6v. I have just put a new battery and alternator on today and reset the bms. I have fault codes for lost communication between alternator. Also code for lost communication between active grill shutters. They are on the same circuit. Going to send it to an auto sparks to look at wiring and possible pcm. I have early mk3 focus 1.6 petrol. 

The absolute minimum voltage from the alternator at any time when the engine is running is 13.6V. Any thing less would indicate a faulty alternator.

Disconnect the small smart charge plug from the alternator and measure the voltage with the engine running at a fast idle. It should be a constant 13.9V which is the alternators default charging voltage when the smart charge is disconnected.

Hi unofix 

thanks for the reply. I went a 50 mile round trip today. Seems like after I reset the bms the battery light is on most of the time. Comes on about 3-5 minutes after starting the car. Voltage was constant about 13.8v. I presume this is down to the fault code saying lost communication with alternator. Any idea on a fix for this? I am quite handy on repairs and electrical work or shall I leave it to the auto sparks. 
thanks again. 

The wires in the connector of the smart plug very often corrode or break. Check carefully the connector and the wires back from the plug for about 120mm. Look for damage to the wire insulation. 

On 5/16/2024 at 12:11 PM, Gill M said:

My 2012 Focus presents the same problem and failed the other day after about 20 minutes of driving with the red battery light on - it usually goes off and I am fine - this time it did not - I was trying to get home and I did but only in first gear at 10 mph for the last mile, as it is automatic and would not change up, I don't think I had hazard lights either although the indicators were clicking in the car as cars following were confused.  When I got home the battery was flat, but we charged it and the car recovered including it's brain and gear functions.  We examined the battery and alternator but both appear to be fine, we called the AA and he put his diagnostic computer on it and he could find no fault.  Took it to the garage following day they looked and found nothing wrong and refuse to replace the alternator as they said it might not solve the problem and it would be £300 spent unnecessarily.  So battery is fine and alternator fine - anyone with any other ideas please?  I am afraid to drive it now as I do not want to get stuck on a smart motorway or anywhere I can't safely pull off the road, especially if the hazard lights wont work.

 

I am having similar issue with my 2012 Fiesta. I took it to a local garage, they thought it was Alternator and changed it, then they changed Spark plugs neither fixed the issue and battery light kept coming on intermittently, engine revs fluctuating badly and eventually the engine switching off. Next I took it to a local electrician who were not competent enough to find anything. Lastly I took it to Ford dealership who first replaced the battery thinking it would fix the fault but it didn't. It took them another 1 week until their master technician found out that it needs replacing two components 1. Throttle body, 2. Main wiring loom (both these caused erratic engine revs when idle). They have quoted me £1,167 parts and labour. I am not sure yet to spend this amount for a 2012 car as I already spent £380 when Ford replaced the battery and £400 when a ***** local garage changed the Alternator and Spark plugs. I wonder what others think I should do, get it fixed through ford with £1,167 or get a second opinion first?

3 hours ago, koira said:

master technician found out that it needs replacing two components 1. Throttle body, 2. Main wiring loom (both these caused erratic engine revs when idle). They have quoted me £1,167 parts and labour.

I'm reading that the Ford 'master technician' only thinks these parts will fix the issue. If the work has not yet been done how sure are they that if you give them £1167 of your hard earned cash that your car will be fully repaired ?

Are they prepared to give you a full refund if after changing the wiring loom and throttle body the car still isn't repaired ?

Also a battery for your car is only about £100 and fitting takes less than half an hour so who charged £380 and for what ?

4 minutes ago, unofix said:

I'm reading that the Ford 'master technician' only thinks these parts will fix the issue. If the work has not yet been done how sure are they that if you give them £1167 of your hard earned cash that your car will be fully repaired ?

Are they prepared to give you a full refund if after changing the wiring loom and throttle body the car still isn't repaired ?

Also a battery for your car is only about £100 and fitting takes less than half an hour so who charged £380 and for what ?

The Ford branded batteries are over £200. That’s not necessarily the dealers fault. 

Ford dealer supplied Fiesta battery finis code 2033185 (52Ah) £111.25+VAT  £133.50

19 minutes ago, unofix said:

Ford dealer supplied Fiesta battery finis code 2033185 (52Ah) £111.25+VAT  £133.50

Maybe the price I had seen included fitting then. I assumed Ford just had a stupid markup on it 

On 7/1/2024 at 8:15 AM, unofix said:

The wires in the connector of the smart plug very often corrode or break. Check carefully the connector and the wires back from the plug for about 120mm. Look for damage to the wire insulation. 

Hi,

I have checked the connector when I renewed the alternator. The plug itself looks ok and the wiring looks like it has been renewed from the plug up to approx. 150mm. I have read that the plug that is next to the radiator under the air box on the passenger side that goes to the grille shutters can cause a problem as one of the wires are on the same circuit as the smart wire for the alternator. Water ingress and corrosion in the plug. So annoying as know I could trace it if I had time to strip it out and test everything but I can't risk not having the car working as I need it for work.

Ok. so now I have some updates. Put a new recon alternator from Halfords in, same problem. Output from alternator is 11.6-14.5V, very erratic up and down. mainly down. Had an auto sparks out and he said to get a second hand genuine ford unit. Done that and the light stayed off and no fault codes, but the alternator had no output at all. I'm thinking it was a dud alternator. Put the Halfords on back and fault codes back up. lost comms with alternator and grill shutters and light back on. I have put a connector on the sensor wire and when it is disconnected I have 14V output constant and the battery light is on. Picking up another second hand unit tomorrow that was tested before it came off the scrap car at 14.7V. Will fit this over the weekend hopefully and report back.

Is there any way to bench test the smart alternator? What module controls the communication to the alternator and can they be tested? Will leaving the comms wire disconnected damage the battery?