Brightening And Dimming Of Lights

[tonydb]

Hey,

Whilst sitting at the lights this morning (5am) I was revving the engine by foot and noticed the headlamps were getting brighter and then dimmer when I released the pedal. I was buying a new battery this evening anyway as the installed one (Halfords own brand HCB-075) this thing was way small in the battery compartment and im not sure it was right for the job? (I may be wrong).

Anyway is this dimming/brightening normal?

Am I being paranoid?

Or is it something someone here has encountered ?

By the way the dimming/brightening is still happening with the correct battery in place.( I went to the local motor spare store and the chap gave me the battery the computer said)

Cheers

[IINexusII]

get the alternator and the ford smart charge system checked, some dimming/brightness is normal but i dont know how much yours is dimming

[Stoney871]

My car dims slightly on idle, never had any electrical faults.

[belewski1984]

Its normal ive had 3 focus a 07 59 and my current 2010 did it on all of them.

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[blue flash]

I've driven 5 focuses, and they all dimmed the lights when the car idles.

[artscot79]

you likely didnt need the battery mate all cars will do this at idle electrics draw a lot of current from the battery and the alternator is not spinning fast enough to replace even a small amount the more electrics you have on the more noticeable it becomes next time pop into a garage and they will do a free battery and alternator test for you

[tonydb]

I got the battery anyway because I don't think the Halfords one was right even though the reg check on Halfords site says it was.Car seems to be responding a little better at certain things.

[Nathan_M]

You could check the voltage at idle and see if it's 14 ish if not then the alternator is being rude, perhaps the auxiliary belt is slipping and not turning the alternator, I notice the smart charge kick in when I switch my lights on as they get a bit brighter after a few seconds and it goes up in phases almost, try the voltage check first, both idle and get someone to raise the revs to something like 2.5k I think I remember correctly that alternators only hit their peak at around 2500rpm

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[artscot79]

given little Halfords do is right that wouldnt surprise me cheaper buying a battery from eBay genuine Bosch silver batteries for around £65 delivered

[Nathan_M]

given little halfords do is right that wouldnt surprise me cheaper buying a battery from ebay genuine bosch silver batteries for around £65 delivered

To be honest my local ford dealer was selling the fiesta battery type for 59 and I brought a Varta Black this time last year for £54 and the Varta puts up with short heavy battery load journeys no problem so far, always reads alright when I test it.

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