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Headlights Brighten On Acceleration

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Hi I have a 2009 1.8 tdci C Max which has a problem with the headlights, they brighten on acceleration as if the battery is low on charge, I changed the battery about 6 months ago and . This seems to happen only first thing in the morning for up to 10 minutes of driving. At times it is so noticeable that I get people flashing me as if to tell me I have my full beams on. Any one got any ideas?

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I reckon the battery is failing. That 10 minutes after startup is the time the alternator needs to top up the charge.

Put a multimeter on the battery when the car's been stood overnight, it should be around 12.6V, going up to around 14.4V with the engine running.

[edit] Just checked and as I thought, like most other Fords, yours needs a Calcium Silver battery, not a regular Lead-Acid. So check that you've got the correct type (it will say "Calcium Silver" or at least "Ca" on it).

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Another sign of the battery dying is testing your headlights. Switch them on before turning on the engines, whilst starting the engine they should dim slightly but not completely go out, if it does your battery is knackered no doubt

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Right I have checked the battery charge before starting and it's 12.5 volts; After I have started the car the voltage drops slightly (12.3v) but does not show a charge from the alternator until I rev the engine to 2500/3000 revs (it's then 14+ volts) .

I checked the connecters on the alternator for signs of corrosion (ok) and noticed that the alternator was very hot, virtually too hot to touch whilst the rest of the engine wasn't even warm (I had only run the engine for 5 minutes or so).

So it looks like the alternator is on it's way out!

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