Battery warning light on 98 V70XC

[clandyuk]

Strange problem has recently occurred on my ageing old bus.

From a cold start, after 1.5 miles or so the battery warning light comes on. It stays on for approx .5 miles and then goes off, never to re-occur until next cold start.

Battery voltage (fairly new battery) is around 12.6v static.

Any suggestions as to what's going on or even how to diagnose this??

Andy

[hal9000f]

Originally Posted by clandyuk

Strange problem has recently occurred on my ageing old bus.

From a cold start, after 1.5 miles or so the battery warning light comes on. It stays on for approx .5 miles and then goes off, never to re-occur until next cold start.

Battery voltage (fairly new battery) is around 12.6v static.

Any suggestions as to what's going on or even how to diagnose this??

Andy

Generator charging voltage? Check it while warning light is on and without...

Should be at least 13.7 - 13.9, or even slightly more than 14.0 V.

When I cleaned and replaced main (also the biggest I believe) GND connector to the engine ony my 1996, 850 TDI, the engine sound was much smoother and less vibrations...

Bad/corroded/dirty GND connection could be the cause of all sorts of (mysterious) issues...

[clandyuk]

Originally Posted by hal9000f

Generator charging voltage? Check it while warning light is on and without...

Should be at least 13.7 - 13.9, or even slightly more than 14.0 V.

According to the Voltmeter in the cigar lighter, the charging both before and after is around 13.9V. At the time the light comes on, it drops to around 11.9V for the .5 mile, then everything back to normal.

Originally Posted by hal9000f

When I cleaned and replaced main (also the biggest I believe) GND connector to the engine ony my 1996, 850 TDI, the engine sound was much smoother and less vibrations...

Bad/corroded/dirty GND connection could be the cause of all sorts of (mysterious) issues...

Yes but surely that would be 100% of the time, not just a .5mile 30sec "glitch" that then goes away until next cold start.
It smacks to me of something that kicks in after a short while of running, finds a problem and then kicks out until a restart after a few hours of non running - maybe something in the alarm system???

Thanks for the suggestions though.

[rabbituk]

When the battery is under load the measured voltage will drop. The 11.9V obviously indicates that the battery is not being charged. When my aux belt idle pulley went causing the aux belt to drop off I had exactly this issue. If the aux belt is not turning and if you are going slowly (say under 10mph) then you will also feel the loss of power steering. Otherwise I as hal has said, it could be a bad ground connection or failing alternator.

[clandyuk]

Originally Posted by rabbituk

When the battery is under load the measured voltage will drop. The 11.9V obviously indicates that the battery is not being charged. When my aux belt idle pulley went causing the aux belt to drop off I had exactly this issue. If the aux belt is not turning and if you are going slowly (say under 10mph) then you will also feel the loss of power steering. Otherwise I as hal has said, it could be a bad ground connection or failing alternator.

Thanks for the comment, but.......
Belt is fine and a bad ground connection wouldn't self-correct after 30 secs surely.

Maybe it is a failing alternator, but again can't see that it would show same symptom for a very short time and then go back to normal charging.

Its been happening like this for the last couple of months but, strangely, only when I reach the same point on the road. Maybe someone's working on some high output electrical "thingy" around there!

Out of interest I started car and let it idle for approx 10 mins. No battery light. Then drove it and again, after 1.5 miles or rest of journey, no battery light.

Will try alternating immediate drive off/idle then drive off to see if there's any pattern that way (joys of being retired).

[rabbituk]

When you say that the belt is fine, are you including in that statement that the tensioner and idle pulley are okay? I think I'm correct in saying that these can only really be checked by slacking off the belt tension and feeling for play.

I agree that the bad ground is unlikely to cause a temporary glitch like you are experiencing.

[Martin Cox]

A bit of a long shot but wear in the electrical part of the ignition switch can cause all sorts of odd things to happen, usually intermittently. One of the odd things can be the battery warning light apparently misbehaving.

If you stop the engine whilst the battery warning light is on, is it still on when you restart the engine? If not, then this might suggest a ignition switch problem. Does wiggling the ignition key have any effect?

This very occasionally (once every couple of years!) happens to my 1998 V70 and I suspect this may the cause. Since the issue has always disappeared after a restart, I've not bothered to investigate any further.

Is there an unusual bump in the road at the particular point you mention. If so then it might just be shaking something, possibly the ignition switch into behaving itself again.

I don't know if this is likely to be of any help or not. Perhaps one for that box of straws to clutch at.



Martin

[Bob Meadows]

https://www.ebay.co.uk/itm/156191349...Bk9SR77RzN6CZA

Car Auto LED Voltmeter Battery Electric Cigarette Lighter Voltage Meter Tester:~
This tester is worth keeping in the glove box for a quick review of the battery/alternator condition.
Bob.

[clandyuk]

Originally Posted by Martin Cox

A bit of a long shot but wear in the electrical part of the ignition switch can cause all sorts of odd things to happen, usually intermittently.

Thanks Martin. Another thing to add to my list of "try this then....."

[clandyuk]

Originally Posted by Bob Meadows

Car Auto LED Voltmeter Battery Electric Cigarette Lighter Voltage Meter Tester:~
This tester is worth keeping in the glove box for a quick review of the battery/alternator condition.
Bob.

Bob, have one permanently in cigar lighter socket. Trouble is I got one with an orange display and that's really difficult to see!

Can see voltage running normally at around 13.9V then drops to nominal battery voltage and then kicks back in after 30 secs or so, never to repeat until (randomly) the next cold start.
Most perplexing, but ultimately not a real problem I guess atm.

Will try the various suggestions over the coming days and report back laters.

Thanks all.

Andy