I recently changed the battery on my fiesta eccoboost 2014, but the battery warning light remains on even after a battery reset procedure.  The rear and front windscreen heaters also appear to be disabled.  It is as if the engine management system as gone into battery limp mode.  Does any one have any ideas on how to reset it without resorting to a garage and hence cost?

46 minutes ago, Davros said:

but the battery warning light remains on

The light is on to tell you that the battery is not getting charged. It's not a battery warning light, it is an alternator warning - back in the day before car manufactures decided that drivers lacked the ability to read, the light used to be labeled 'Gen', as in generator.

Have you measured the voltage with a meter at the battery terminals? It should be at least 13.6V with the engine running. If it is less that you need to get the alternator tested.

I measured the voltage across the battery with the engine idling and it was 13.65 V so it could be borderline alternator output. I will measure again, but with engine at higher revs.

16 minutes ago, Davros said:

with the engine idling and it was 13.65 V

If the voltage across the battery terminals is 13.65V at idle then I would say that's OK. It would seem possible you have a fault with the smart charging circuit. If you look at the alternator you will find a small connector that has two or three wires, that is the smart charge plug.

With the engine off, disconnect the smart charge plug (it just un-clips) and carefully inspect the wires and the pins for any signs of corrosion or breaks in the wires near the plug.

Leave the smart plug disconnected from the alternator and start the engine. Measure the voltage across the battery terminals, it should be 13.8V at a fast idle. This is the default voltage of the charging circuit if the alternator smart system fails.

Let us know what you find.

 

10 hours ago, unofix said:

If the voltage across the battery terminals is 13.65V at idle then I would say that's OK. It would seem possible you have a fault with the smart charging circuit. If you look at the alternator you will find a small connector that has two or three wires, that is the smart charge plug.

With the engine off, disconnect the smart charge plug (it just un-clips) and carefully inspect the wires and the pins for any signs of corrosion or breaks in the wires near the plug.

Leave the smart plug disconnected from the alternator and start the engine. Measure the voltage across the battery terminals, it should be 13.8V at a fast idle. This is the default voltage of the charging circuit if the alternator smart system fails.

Let us know what you find.

 

Thanks for that, i will investigate and get back.

On 4/25/2022 at 9:24 AM, unofix said:

If the voltage across the battery terminals is 13.65V at idle then I would say that's OK. It would seem possible you have a fault with the smart charging circuit. If you look at the alternator you will find a small connector that has two or three wires, that is the smart charge plug.

With the engine off, disconnect the smart charge plug (it just un-clips) and carefully inspect the wires and the pins for any signs of corrosion or breaks in the wires near the plug.

Leave the smart plug disconnected from the alternator and start the engine. Measure the voltage across the battery terminals, it should be 13.8V at a fast idle. This is the default voltage of the charging circuit if the alternator smart system fails.

Let us know what you find.

 

The alternator has 2 connections 1 -  thick red wire 2 - thin purple wire . Also there is a current sensor on the neg terminal of the battery that is connected to the ECU.