407 es9 v6 -battery warning light comes on when really cold

[407]

So I've had the battery waring light come on a fe wtimes in the last few weeks but only in the mornings on the way to work when its cold (eg 7/8 C) and only after driving say 1 km.

Car starts fine.

I tend to turn around to go back home (just in case) but half way back home it disappears.

Ive stuck a voltage monitor and it read 11 volts when the battery light is on but 14.3 volts when it goes out.

Ive disconnected and refitted any cables I can find just it case it was a connector issue.

MIL light does not come on

Alternator was rebuilt a year ago and has been running fine since then and battery is a year old

Any ideas ?

[GiveMeABreak]

There's obviously a problem with either the alternator or the charging circuit if it is intermittently charging. I'm assuming you've checked the battery terminal cables and traced these back and checked the earthing points?

[xantia_v6]

I suspect that there is a fault in the rebuilt alternator, perhaps sticky brushes. If it has a warranty, I woul exercise that option first.

[Rp0thejester]

I would definitely check the alternator first. Only thing I would question after that is what time do you leave for work, could it of reached 0 degrees? If so I would look at putting a battery quilt/jumper/insulation box around the battery.

[PaulC5]

I would check the battery voltage in the morning before the engine is started just in case it is faulty or needs a full charge due to short trips. Fully charged it will be about 12.7 volts but lower than about 12.5 volts needs charging.
Previously I have looked at the effect of low temperatures on battery voltage and it barely makes a difference so covering the battery with a blanket should not be needed.
You can also check for a slipping auxiliary belt for the alternator.

[Rp0thejester]

I would check the battery voltage in the morning before the engine is started just in case it is faulty or needs a full charge due to short trips. Fully charged it will be about 12.7 volts but lower than about 12.5 volts needs charging.
Previously I have looked at the effect of low temperatures on battery voltage and it barely makes a difference so covering the battery with a blanket should not be needed.
You can also check for a slipping auxiliary belt for the alternator.

Thanks for that info, as I don't use my car much I found battery drain was an issue in cold weather

[407]

Just to close this off

Other than putting this issue up onto the forum, I did nothing and the issue has not reappeared albiet it may have got a bit warmer since then.

Seems putting it up on the Forum is a better option that trying to fix it

[xantia_v6]

I just had a thought that it could be the rubber section of the crankshaft pulley is delaminating
It is very common on these engines, but usually they squeel when cold. Paint a radial line on the face of the pulley from the inner to the outer section and check occasionally that it hasn't slipped.

[407]

An interesting end to this story some 14 months later.

During that time the low battery warning light came on and off a few times

Last week on a 46 C day, it came on, went off and then stayed on.

I managed to drive home 50kms trying not to use any electrical power (eg air cond)

Pulled the alternator off and found the slip rings / brushes caked with crud.

Also the lower slip ring as pretty worn and the lower brush was short so suspect they gave up contact.

Cleaned it up, unsoldered the lower brush to extend it a bit and refitted. Now have 14.2 volts

The worst part of this job is that you need to undo the airconditioner compressor and let it hang as the alternator is fitted above it.

I had this alternator "rebuilt" some 3 years ago but now suspect they just cleaned it up, painted it and handed it back, no new parts at all. I've only travelled some 30,000 kms since that so would not expect that much wear or crud in new components, esp as the warning light has been coming on for some time

Once summer is over, I'll rebuild it with new components which I found as per pics