Electrical failure - car stopped on motorway

[Redwolf]

Hi Guys. First time post, hope you can help.

2017 Audi Quattro A4 Avant 2.0 Diesel S-Line

This is my daughter in law’s car, and I am trying to help diagnose the fault but know we will probably need to take to an auto electrician. Just wondering if anyone has seen this before and knows the issue.

 

Driving along when suddenly (with no notice) the car lost all power (Electrical). Engine stopped, no power steering, no indicators/hazards, no dash lights. Managed to get to the side of the road and called breakdown services (AA).

Their mechanic said it was extremely hot under the bonnet and the ECU was particularly hot. There was no power from the battery and the mechanic tried to jump the car using a booster pack. When he connected the booster under the bonnet (battery as you know is in the boot) and connected the earth there were sparks and the booster tripped out. The mechanic suspected something between battery and front of the car where he connected the booster was shorting and she was lucky the car did not set on fire!

The car was recovered and taken back to house as no garages were open at this time.

We have now performed some further checks as below:

With everything connected

1.      Multi-meter across the charging/jumping terminals under the bonnet, and it showed Zero (0) Volts!

2.      Removed the spare wheel and tested across the battery terminals, again it showed Zero (0) Volts

3.      I then set the Multi-meter to Ohms and checked for resistance\shorts. I performed the same check directly across the battery terminals and under the bonnet. These both showed no resistance indicating some sort of short of the positive to earth.

Positive Terminal Under Bonnet Disconnected.

1.      Again, using the Multi-meter set to Ohms and checked for resistance\shorts between the disconnected positive cable and to earth now showed resistance.

2.      Did the same test from the Positive terminal of the battery (with the positive cable under the bonnet still removed) to earth and it also showed resistance. This indicated some sort of short of the positive to earth when connected.

3.      This suggested that any problems are on the engine side rather than the battery or cable to the engine bay.

Both terminals removed from the battery

1.      With the Multi-meter still set to Ohms and cables disconnected from both the battery and the positive in engine bay it showed resistance

2.      With no battery terminals connected I decided just to have a final voltage charge across the battery and to my surprise this showed just over 10 volts.

 

Any help appreciated.. Kev