Winter Check Your Battery-Alternator Junction Box

[DaveJH]

The heavy current lead taking the Alternator supply to the Battery is interrupted by a Junction Box/Fusible Link Box which is located at the front of the engine bay just under the battery cover.  It is takes only a moment to check the condition of the box, and press in the side clips to check the terminal lugs.

 

The compression lug on the cable from the alternator can deteriorate with age increasing its resistance and causing it to heat up. This then enters a vicious cycle: the heating causes the lug resistance to increase, which causes more heating etc.  Eventually the alternator current will be so restricted that the “Alternator Workshop” warning light will come on, plus VAG codes associated with low supply voltage at the ECU etc. 

 

The problem is that the heat generated by the terminal may do significant damage before the Alternator Workshop symbol alerts you to the problem.  In my case not only was the inside of the terminal block and cables damaged, but also the top of the terminal box was burnt through allowing heat to escape upwards. (See photos - if I manage to upload them correctly).

 

Excellent details of how to replace the box and repair/replace the cables can be  found in the thread for “Alternator Workshop”.