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Discussion Starter #1
Hi guys!

My 2005 GT JTD with 95000 km on the clock developed an issue, whereas it's lights (interior and exterior as well, I have some LEDs installed it's more visible in them than in the halogen bulbs) are flickering while the car is idling. If the engine is not running or is at a higher RPM (around 1500-2000) the lights are 100% fine. Last I checked the voltage via MultiECUScan it was 13.9 volts. Shouldn't that be 14.4?

Also, any ideas where the problem comes from? My bet be would be the v-belt (even tho the manual says it should be changed around 120k km it's still a 13 old rubber belt)
 

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sounds like a problem with either the battery or charging circuit.... Could be the v-belt as you suggested.... As i's old, and not expensive, I'd change it anyway....

Also check battery connections and ground points.

LED lights are more susceptible to voltage variations (and react faster), so you would notice it there first.
Filament bulbs inherently tend to avarage out fast voltage variations
 

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Discussion Starter #3 (Edited)
sounds like a problem with either the battery or charging circuit.... Could be the v-belt as you suggested.... As i's old, and not expensive, I'd change it anyway....

Also check battery connections and ground points.

LED lights are more susceptible to voltage variations (and react faster), so you would notice it there first.
Filament bulbs inherently tend to avarage out fast voltage variations
The battery is around 7 months old (about 10k km ago) and when it was replaced if I recall correctly the charging was good, at 14.4 volts. What happened since is that I installed a reverse camera with my electrical engineer father so I assume he knows what's he's doing when it comes to putting a few consumer (total of 5 watts I think) on a circuit.

Also, when it comes it the alternator, how likely for it to fail?
 

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Alternators can fail anytime it’s luck of the draw.

Double check earth pionts from battery to body and engine for corrosion. Add a jump lead from battery earth to engine see if that makes a difference.
Also make sure battery pos connections are clean and tight.
 

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My money would be on the alternator. Once the engine is running all electrics run off the alternator so that would rule out the battery. MES may show 13.9 volts, but it's refresh rate is not realtime, it only polls once every second or so, while a LED bulb will react to a sudden voltage drop in a fraction of a second.
 

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Is the flickering rate proportional to engine speed?
If so, then it sounds like a diode in the alternator has failed and full wave rectification is no longer happening and the voltage drops out as one of the 3 field windings is effectively backfeeding (producing reverse voltage).

An alternator change is not a popular job and is a rather lengthy process.
Disconnecting rear and timing belt end mountings makes the job possible.
 
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