Lights flickering when idling

[ZilogJones]

Since I've got my 406 a few years ago I noticed sometimes the headlights flicker momentarily every now and then, but in the past few months I've noticed the problem get a lot more severe and now the flickering is almost constant and more erratic.

It seems to happen with all lights - interior and exterior - although I don't notice it much with the instrument cluster or centre console lights.

It only happens while idling - if the engine is at any higher speed everything seems fine, and with the engine off there is also no flickering.

Any ideas? Could it be the alternator or something related?

[lozz]

hi,
have a battery test done,also alternator,

alternator couid have a iffy diode,

[PeterN]

Connect a meter across the battery, you should have a steady reading of around 14.4 volts with the engine running, if its varying much you probably have an alternator problem. It could also be caused by a bad connection or slipping drive belt.

Peter

[fattail95]

I had the exact same symptoms in my old Mini, lights pulsing/flickering. It was the diode on the alternator that had packed up, and the electrical system was running at ~17volts! Eeek! Get the alternator checked ASAP.

[ZilogJones]

I checked with a multimeter and it was fluctuating between around 14.0 V and 14.6 V depending on load. Surely modern cars like this have voltage regulators and the likes to avoid damage to the ECU and all that? But yeah I must get it checked out properly.

[PeterN]

That sounds to be within the acceptable range if its load dependent, if there was a fault the voltage would vary with a constant load.

Peter

[ZilogJones]

Sorry, just to be clear it is continuously fluctuating with a constant load, but the range of fluctuation increases with a greater load (more lights, rear window demister, etc.).

[PeterN]

Ah right, sounds as though you have an alternator problem then.

[Captain Jack]

Also check that the clutch pulley on the alternator isn't seized as it would cause uneven rotational speeds during idling...

[ZilogJones]

I took it to the mechanic, and he didn't think the flickering was significant enough to be of concern. Clutch pulley seems ok, although there seems to be some clicking from somewhere (belt tensioner?) after starting, which he also said is normal enough with these engines at this age. Battery is charging fine. He ran a new earth lead as a precaution (something to the gearbox?).

I guess the voltage regulator(s) are on the way out but not really bad enough to worry about yet? Are these like linear regulator ICs, or diodes or what? And is it possible to replace any of that stuff? I've done soldering on computer PCBs but never any car stuff...

[PeterN]

I think you can get regulators on ebay for not to much money.
http://www.ebay.co.uk/itm/BOSCH-ALTERNA ... 2a307a1da3

Peter

[ZilogJones]

Oh, that looks nice and modular

I see there's a few different possible Bosch or Valeo alternators that could be fitted to my 406 - I guess I would need to find out which one first. Service Box lists a regulator component for each one.

Does anyone have experience dismantling alternators? Is it difficult? And is there anything else besides the voltage regulator that could be causing these symptoms?

[PeterN]

I think you can change the regulator without dismantling the alternator, they fit on the back if my memory serves me correctly. You will need to check what type you have although the same parts are used on different alternators.

Peter

[ZilogJones]

I ended up not doing anything about this issue, until earlier this month when the alternator pulley started making an awful racket. As I said last year it would sometimes click when idling, but it suddenly got very noisy when cold and at idle speeds. At least it didn't spontaneously disintegrate, like on my friend's Leon!

After replacing the pulley, I have no more flickering lights, idling seems smoother and the engine no longer shudders when starting/stopping.

[PeterN]

That's good to know

Peter