Hi, my mondeo is just over 6 years old so when the AA man pronounced the battery dead after a call out for a non start I was not surprised. However, about a month later the new battery is flat and the car won't start. If I charge the battery up it seems ok, but does not really seem to charge properly from the engine. When I check it the battery with a meter it is about 12.6V. Once the car is started it takes about 13 seconds for the terminal voltage to rise to 14V. Is this normal? I would expect the alternator to put out 14V immediately the engine is running. Is this a symptom of a faulty alternator?
Hi, I have done some more tests as requested. At 2500rpm with full load the battery voltage is 14V so charging Ok. However, at idle with full load the voltage is only 12V so not charging. No sound of slipping drive belt - which seems tight and was replaced recently anyway. I presume that something is wrong with one of the alternator "smart" charge modes. Thanks for the advice. Cheers Peter
That sounds fairly normal, when you have just started the engine the battery resistance is low and demanding more amps than the alternator can provide at that speed, as the voltage comes up the current demanded drops so the voltage rises, same situation with a full load and low revs.
Mondeo Mk3 V6 - Battery charging problem - alternator fault? -
I run a v6 mondeo,and checking the voltages on mine,I would say that yours is a little on the low side at idle under load.I don,t think this is an alternator problem as usually this would be indicated by an illuminated warning light.What I have found to be more likely on these is the main battery terminal where it bolts on to the back of the alternator can overheat and cause a bad connection and thus a volt drop.Also check the temperature of the plus/positive terminal on the battery to see if it it excessively hot with engine running.hth
Hi, thanks to everyone for their help. New battery now fitted under warranty by the AA. Voltage at idle is 12.75V, but any revs and this increases rapidly to 14V. Seeing as you don't drive at idle this should be OK. The battery warning light has never come on, so I would have to agree that the alternator is OK and the battery was just not holding the charge. I did notice that the AA batteries are standard lead acid where as the original Ford one was Calcium. Would this make a difference? Cheers Peter
I read on t'Internet that some battery manufactures claim that their batteries, whilst not Silver Calcium, will take the extra voltage of a Smartcharge system and work in Ford cars. A friend of mine had the old, failing, Silver Calcium battery in her Focus replaced with a cheaper, standard battery - which the Smartcharge system destroyed in just a few weeks.