Battert light on when accelerating

StuBailey · Jan 20th, 2007, 14:56

Hi need some help,
I bought a 2nd hand 2001 V40 last week initially really pleased with it, but today I've noticed the battery light is coming on when I accelerate then goes off as soon as i'm at a constant speed or braking. Anyone got any idea why? Have i got an alternator problem?

Thanks.

gnhuk · Jan 20th, 2007, 15:21

Loose auxiliary drive belt................ or possibly the drive pulley on the alternator?

stephen-in-hull · Jan 20th, 2007, 18:09

Could be a loose connection close to the alternator.

Check first to see if the alternator is well anchored, and the drive belt is tight enough, then try and find something that acceleration would cause to move. It might be something not directly connected, like an engine mount rotted or broken, that allows the engine torque to allow the engine, and alternator, to lurch to one side, putting a strain on alternator to battery wiring.

You could check the latter theory by having a rev up while stationary, and see if it's same as on the open road. Don't forget that connectors can look good, but occasionally have a duff contact lurking with poor or high resistance, or intermittant open circuit. Get an assistant to rev the engine a little at rest, while you twiddle under the bonnet.

Good luck.

Viper_7 · Jan 20th, 2007, 18:40

A bad earth can cause this too , also alternator regulator.

What's the condition of the battery?

Jan 20th, 2007, 14:56	#1
StuBailey New Member Last Online: Aug 13th, 2009 11:52 Join Date: Jan 2007 Location: Milton Keynes	Battert light on when accelerating Hi need some help, I bought a 2nd hand 2001 V40 last week initially really pleased with it, but today I've noticed the battery light is coming on when I accelerate then goes off as soon as i'm at a constant speed or braking. Anyone got any idea why? Have i got an alternator problem? Thanks.

Jan 20th, 2007, 15:21	#2
gnhuk Balding............. Last Online: Jun 29th, 2018 10:35 Join Date: Dec 2003 Location: Linslade	Loose auxiliary drive belt................ or possibly the drive pulley on the alternator? __________________ Gavin VOC17969 2000 S40 1.8S -with various options (Now sold @135k miles) 2012 S40D3 R-Design

Jan 20th, 2007, 18:09	#3
stephen-in-hull stephen-in-hull Last Online: Sep 22nd, 2007 14:09 Join Date: Jul 2006 Location: Kingston-upon-Hull	Loose connection Could be a loose connection close to the alternator. Check first to see if the alternator is well anchored, and the drive belt is tight enough, then try and find something that acceleration would cause to move. It might be something not directly connected, like an engine mount rotted or broken, that allows the engine torque to allow the engine, and alternator, to lurch to one side, putting a strain on alternator to battery wiring. You could check the latter theory by having a rev up while stationary, and see if it's same as on the open road. Don't forget that connectors can look good, but occasionally have a duff contact lurking with poor or high resistance, or intermittant open circuit. Get an assistant to rev the engine a little at rest, while you twiddle under the bonnet. Good luck.

Jan 20th, 2007, 18:40	#4
Viper_7 Premier Member Last Online: Aug 30th, 2013 17:33 Join Date: Apr 2006 Location: York	A bad earth can cause this too , also alternator regulator. What's the condition of the battery? __________________ S60 D5 SE 2004 Titanium Grey Winter Pack Mods: Volvo Tax disc holder - increases power output by 5% Child Seat Rear and side Volvo fitted blinds. Tree Sap from May - July. Removed at least 46 cup holders for weight reduction.

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