Thread: 300tdi intermittent battery light flashing on and off?

Loose connector somewhere.

I know you said that it is a new alternator, but you do have the same symptoms as either worn or stuck brushes. Have you gone through mud recently?

Aaron

Nah no mud at all. Bit of dust maybe. Loose connector being just one of the ones on the back of the alternator? Can I clean the brushes with contact cleaner or similar?

Originally Posted by TOR

Nah no mud at all. Bit of dust maybe. Loose connector being just one of the ones on the back of the alternator? .....

Yeah, the first obvious lace to look, having recently fitted the alt, would be the connections on the rear.
Also look for signs of weakness on the smaller thin wire where it's connected at the eye connection too.
So not just the tightness of the eyelets on the alternator, but the surety of the wire on the eye itself.
Maybe in removign and replacing it, it's weakened a little and the recent work pushed it over the edge.
Those wires do get hot over time and then brittle .. don't need much to push them beyond a good connection.
Those are the easiest checks in terms of time and effort

Sounds like it's intermittent, not the causing trouble all the time.
You say that the volt meter reads 0.5v lower than, if it does it again and you get a chance place a decent quality multi meter on the battery and see if it fluctuates by any amount.
I've had issues where hotter running(like on a freeway, or up a long hill) caused the diode pack/regulator to cause charge issues, Then when running slightly cooler, it ran fine.
That was on an old Fontera tho. It's rear face is also a little close to the exhaust too .. like on a Tdi.

May well be brushes as posted in another reply, but on a new alternator, less likely.
Diode packs OTOH ... they can fail prematurely, I'd say more likely.

Even less likely, but not impossible .. maybe a spinning pulley!
Not very likely, but as it's happened to me a couple years ago ... it's not an impossible occurrence.
Pulley didn't come off, but came loose on it's shaft, so it spun 'freely'.
The tension of the tensioner did force it to run, and hence charge, and the only telltale I had that something wasn't right was (in a D1) the revs increased by about 500RPM more than I'm used too at set speeds.(eg. at lockup in 4th).
No noise, nuthin .. just higher revs .. and then noted the alternator pulley.
For clarity tho, the broken pulley/shaft was due to excessive strain on it by the failing harmonic balancer. Alt was less than a year old, but nearly 30K klms use.
A little later the power stg pump also started to leak too .. so I'd estimated that the harmonic balancer did the damage .. not that the new alternator brand was somehow less durable.
Replacement(warranty) is still going now, about 2 years, maybe 50 or so K klms under it's belt.

If any of the above fail to cure it, then the harder check to dig into would be the dash bulb itself.
This possible cause would be a slightly loose plug/connection at the actual lamp.
I've only read about it being a problem via Britannica restorations, where he sorts out the flickering warning light on the dash. IIRC he sorted a connection at the multiplug behind the dash.

Battery earth issues can cause this.

make a new earth cable and go from the motor to the battery. If that fixes it you need to look for earth problems on the motor/gearbox.

is your hand brake cable playing funny buggers?

Originally Posted by Blknight.aus

Battery earth issues can cause this.

make a new earth cable and go from the motor to the battery. If that fixes it you need to look for earth problems on the motor/gearbox.

is your hand brake cable playing funny buggers?

WOW,
that seems left field, im guessing you've seen it before though?

Originally Posted by shack

WOW,
that seems left field, im guessing you've seen it before though?

yep, usually though by the time the battery light is flickering the bad earth is either the first in a chain of or the last link in a chain of failures.

but you've got to start somewhere, the simple engine to chassis/body earth is the quickest and easiest to eliminate by means of a jumper cable going from bat negative to the AC bracket or the alternator body.

sometimes its not the engine earth its the body earth or the dash earth.

G'day all, I have a similar problem with my '98 300 Tdi. Occasionally, the warning lamp glows faintly, so faintly it's hard to detect in daylight, but noticeable at night. Battery voltage doesn't seem to drop however. More likely to occur when everything's warmed up, or say at the top of a steep climb at say 40 KmH. I'll check earth connections as suggested in this Thread, but I'd like to hear from anyone else who's experienced this problem.
Cheers, Rob S