Hi I changed the battery on my partners fiesta and I accidentally pulled the yellow and brown wire out, which is connected to the live terminal, just wondering what it’s for as it seems her stop and start isn’t working now, I’ve added a pic

Thats probable  what its for reconnect it to see 

That's the BMS, it measures battery charge, so that probably will be the reason the stop start doesn't work with the new battery.

3 hours ago, Wpd said:

I accidentally pulled the yellow and brown wire out,

Oh dear, first you need to go to Spec Savers, that wire is Yellow with a Violet stripe 😉

After fitting the new battery did you carry out the reset of the BMS procedure ?

For reference: That's the 3 Amp Fuse holder. The BMS sensor is located on the battery negative lead.

After checking the schematics for your Fiesta, it looks like you have pulled the wire out of the 3 Amp fuse holder which is attached to the side of the battery positive.

If you open up the in-line fuse holder it should be possible to re-attach the wire to the fuse. You will need to do that before resetting the BMS.

Don’t have my glasses on, no I didn’t reset the nms as I didn’t know what that was 

I thought it was a straight forward swap any help would be appreciated 

8 minutes ago, Wpd said:

I thought it was a straight forward swap any help would be appreciated 

First you will need to fix the broken wire and reattach it to the fuse inside of the holder. It's probably a good idea to disconnect the battery cable before trying to do that.

Once you have fixed the wire, then you need to reset the Battery Monitoring System - BMS

It will be one of the two methods shown in the videos below. You will be able to tell which one is for your car by looking at the type of headlight switch fitted. Make sure you have the drivers door closed when resetting the system.

On 3/29/2023 at 8:13 PM, unofix said:

How to reset the BMS method 1                                                                         Search Tag: BMS1

 

 

On 3/29/2023 at 8:14 PM, unofix said:

How to reset the BMS method 2                                                                         Search Tag: BMS2

CAUTION: The reference at the beginning of the video saying that the BMS should be reset after charging the battery in incorrect.

The Battery Monitoring System (BMS) should only be reset if a new battery has been fitted.

 

Ok thanks I will have a look

How do I access the videos

videos have come through many thanks