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Intermittent Battery Light on 2008 Mk6.5 1.4 Petrol


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Hi all, hoping for some help.

tl;dr Got an intermittent battery light whilst driving, multiple occassions. Car is driving as normal anyway. Any ideas?

The Car is a 2008 Mk6.5 1.4L Petrol.

Turning on the car, all the dash lights behave normally.

Beginning this week, Sometimes about 5-10 minutes into the drive, usually once the coolant is up to temp, the battery light turns on. I then turn my (aftermarket) radio off, and about 2 minutes after that, the light goes out. However, the light has also come on while I've had the radio off. This is city/dual carriageway driving, although I've done a couple of 60-mile motorway trips just before this issue.

Other than the light itself, the car feels absolutely fine.

Questions:

1. Does this model of Fiesta have a "Smart Charge" Alternator? Have seen confliciting views and I can't work it out from the images of alternators/batteries on parts stores; my haynes manual mentions nothing about it either.

2. If the car feels fine anyway and doesn't struggle to start, is the light just a forewarning that my battery is reaching the end of it's life?

3. Have re-bought a tunnelrat OBD after losing my first one; will it show any codes for why the light is on?

Thanks,

Fisher.

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I've done a code read - got a P0620 from the PCM, "Generator Control Circuit Malfunction". Not sure where to go next with fixing it, so likely time to head to a garage.

I hit a pheasant whilst driving about 2 weeks ago - couldn't see any damage, but when I got home I checked and found that some heatshielding towards the rear was a little bit loose - could be causing a short somewhere?

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Hi Fisher, it is probably just the alternator starting to wear out. With the engine running at normal temprature and just at idle speed switch on your main beam headlights, and your heated rear window (put the heated front on as well if you have it). Does the battery charge light come on ?

Increase the engine speed to about 1500RPM if the battery charge light was on, does it now go out ?

You can get a reconditioned alternator for about £85 with a years guarantee from lots of electrical automotive dealers. I see you are in Yorkshire and I know there is an alternator refurbishment place in Leeds.

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Thanks both for the replies, haven't had much chance to check it out due to being tied up in Uni work. Given the fault from the PCM, the small plug's wiring (smartcharge loom, as far as I understand) is the culprit in my gut reaction, so I'll start by checking that.

@Brett Ski - you wouldn't happen to know the price on replacing the wiring, would you? I'll try to do it myself if I can get my hands in, but if I can't it would be nice to get a rough estimate of what it'll cost me.

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smallplug.thumb.jpg.d2678d7f118dc639e47d45c5234925c4.jpg

This is what my small plug looks like - I can't see any damage on the wiring that's visible without taking the sheath off; which will be my next step.

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On 4/16/2021 at 3:17 PM, unofix said:

With the engine running at normal temprature and just at idle speed switch on your main beam headlights, and your heated rear window (put the heated front on as well if you have it). Does the battery charge light come on ?

Increase the engine speed to about 1500RPM if the battery charge light was on, does it now go out ?

Did you try this ?

What happened ?

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Haven't tried it yet, didn't go for a drive and didn't want to sit around polluting. However the light is coming on regardless of load. Still, I'll test this out when I next drive somewhere.

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@unofixtried it today - the light was on before, after a drive. Engine was up to temperature.

Parked up and turned on my low beams, and the rear heater - my front heater wouldn't turn on, I believe due to the light. The light remained on.

I revved up to 1500 a few times, and held it there for a good 10 seconds - no change, the light stayed on.

As I've said, the light seems to be independent of load, which is why I think it's the plug.

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Sounds like your battery voltage is getting low now. You definitely have a charging fault. I think it is probably the Alternator failing, it could be that the excitation field is being turned down to nothing by the charge controller. 

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