XSeries-forum

Hi all,

I would welcome your thoughts ope my current problem with my E53 3.0 D sport.

We had a new BOSH battery fitted four weeks ago after the previous battery rand down weekly. We do very little milage 4K to 5K a year.

The car has had moments where it does not start first turn, then most days starts fine.  However this morning the battery is flat, low voltage at the battery, however i have noticed that the positive charging point is red hot. HAs anyone experienced this and what is the likely cause / fix.  Thanks for your time in advance.

That point is only a connector for the wiring between the starter, battery and alternator, so if it is hot that implies high resistance or high current passing through it.  It could be corrosion, a breaking wire (current flowing through fewer copper strands so they get hotter) or a bad or loose connection.  It could also be a failing starter motor.

Check that point is both corrosion free and fully tightened, and also (carefully) check the temperature of the positive feed to the starter motor.  If the connection is dirty or loose disconnect the battery and then clean the terminal before reconnecting the battery - that point is directly connected to it!

The starter will draw a lot of current (~180A) but only for a few seconds so unless trying and trying to start the engine, it should not get overly hot.

It is unfortunately common for starters made by Magnetti Marelli between 2003-2005 to suffer an internal fault and draw huge amounts of current that the battery cannot deliver!  My E53 was trying to draw 900+ Amps from a battery only capable of 830A, and our similarly engined E46 starter failed drawing more than 500A.  Replacement is your only option.

Symptoms are sluggish starting, or no starting.  You might also get a very hot starter cable and that charging point along with it.  Check your battery voltage too.  The starter will drag it down very fast but it should bounce back to at least 11.6V.

It is not unknown for even brand new Bosch AGM batteries to fail prematurely.  We had a spate of these about 3 years back, but none had this same hot charging point symptom.

Oh and to the Forum 

Thanks so much for taking the time to respond. My wife thinks its an excuse to buy a new X5.  Your help will save me 1000's.

Kindest regards,

Harjit