MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGF Technical - Battery not rechargeing

Hi!

For some weeks now the battery (three months old) of my F seems not to be recharged when I drive. I had to take it out last week and recharge it with a battery-charger at home :-(

I'm going to check the cables at the alternator (?)
and starter. Are there any other cables I should check? Is there any other device responsible for charging the battery?

Any other hints?
Andreas Holzhammer

Are you sure its not charging. It could be draining. If its not re-charging properly the battery warning light on the dash should illuminate, as it does when you first switch the ignition key on. If its draining it could be to do with the alarm which has been discussed on here before.
John
JFK

Hm, I forgot to mention...

I first noticed it when the car did not start that
easily. And it got worse whenever I wanted to start
it again, even if I drove some miles in between.
This made me think it would not recharge.

The car is three years old and I didn't have the
"draining problem" yet. Is there a way to measure
the power drain of the locked/idle car?
Andreas Holzhammer

It could even be the battery itself, rather than not being charged it may not be holding a charge. This will most likely be the case if no warning lights are showing and it is difficult to start even after a run. After three years it is fairly normal for a battery to suffer degraded plates, sulphation or even a dead cell. Get the battery 'Drop' tested by any local garage to check this possibility out.

Nick.
Nick

Maybe your F is suffering the same problem as mine does.
Check out the discussion on "Severe Battery problem".
MEMs needs to be changed.

Kris.
Kris

A simpel check can be made by checking the various system voltages at different times. A fully charged battery with everything switched off should show about 12.5 volts. Once that shows less than 12 volt is in a poor state of charge.

Next when the engine is running you should see a significant rise in voltage when there are no electrical loads imposed. This will raise the voltages up to the 13.7 to 14 volts area. Note that if the battery is discharged and the alternator works correctly then the voltages will be half a volt or so lower owing to the fact the batery will be drawing a heavy work load from the alternator.

The test of an alternator is to place a reasonable electrical load in the system. This means that you should have dipped headlamps on along with the heater motor on max. Run the engine to 3000rpm and hold it there for 1 minute. During this time I would expect to see above 13.25 volts. If it is below 13 volts then it is reasonable to summise that the alternator is faulty. Note that this check overcomes the common situation whereby a faulty alternator, which can't provide a decent charge level under load, is able to show charge when it is not put under load.

If the charge level is poor then before assuming that the alternator unit is the faulty unit, check the main power connection on the back of the alternator body. These can corrode, create a high resistance and block current flow. The same principle applies to the point where the main alternator power wire to the starter solenoid, and the main battery connections. Also check for a clean battery to earth and a sound earth connection between the engine/transmission and body.

Rog
Roger Parker

Thanks, I tested all this, and it looks like the alternator is gone. It only delivers 12.3V when
the engine is running :-(

Now to the second problem, it seems difficult to impossible to get an alternator for the
F here in germany from the usual "car supplies store" (i.e. ATU). They just can't find
it in their lists, and even the "Magneti Marelli 11 5i 85" (from Dieters excellent pages)
doesn't help...

Does one of the 200 Series Rovers use the same alternator, or do I have to get
the (supposedly expensive) original spare part from my friendly Rover dealer?

Andreas
Andreas Holzhammer

This thread was discussed between 07/06/2000 and 13/06/2000

MG MGF Technical index

This thread is from the archive. The Live MG MGF Technical BBS is active now.