Can the SYNC drain the battery on my Fiesta ecoboost?. I've just put a new Yuasa battery in after the car wouldn't start last week. Its been on my drive for 2 days and the car failed to start. Wont even crank the engine. Just makes a funny electrical buzz for half a second. I did manage to jump start it once this afternoon but it now refuses to even start with a jump

3 minutes ago, Kevin Williams said:

Can the SYNC drain the battery on my Fiesta ecoboost?.

It is fair to say that anything electrical can cause a drain on any car !!

Firstly when you fitted the new battery did you fully charge it for 12 hours?  Did you reset the BMS (Battery Monitor System) so that the car knows it now has a new battery.

So before looking for the holy grail and finding a parasitic current draw that you may or may not have, do or re-do the steps above first.

Yep battery is charged and yes i pushed the fog light switch 5 times then the hazard lights 3 times. The battery light flashed. I guess that was correct. I now have turned off the Bluetooth on the stereo 

What is the battery voltage measured at the terminals ?

It was a brand new battery and i was assured it was fully charged. If i can get it going im taking back to the dealer as ive only had it 1 month and it has failed to start twice now. I just wondered if anybody else has had the same problem 

2 hours ago, Kevin Williams said:

I now have turned off the Bluetooth on the stereo 

You'd probably need to physically unplug the module to stop it having an effect on the battery.

Anyway, you need to do a proper parasitic draw test instead of guessing it's the Bluetooth module.