406oc.co.uk

Sorry to post it on here but my grandmother has a 56 plate Volvo S40 and the battery keeps dying overnight. She also had the alternator repaired a couple of months ago. What could be the cause?

The battery itself? If a battery has a bad cell it can give the appearance of a dud alternator (12v across the terminals with the car running) I've even experienced this fault with a new battery. Also the was a volvo corner on here somewhere [emoji57]

Maybe the battery is too tired/old to hold charge for long, or there is a light on in the boot/glove box or something silly like that...

Check if it's charging properly - you should get 14 to 15 volts across the battery at tickover. If you don't check for voltage at the alternator, (find where to measure with the engine stopped / be very careful not to get caught in the belts while testing).

If it's OK at the battery, switch on a few loads, (headlights, rear window, blower) and make sure you've still got over 13 volts at say 1500 RPM.

Assuming all that's OK, either the battery is dying or something on the car is discharging it. To prove it, find out how to safely disconnect the battery, (like our 5-minute rule for 406's), disconnect it in the evening, then re-connect in the morning / try to start it.

Won't start = new battery time.

Starts OK - something on the car's draining the battery overnight.

Check as much as you can from above, post the results.

I know the alternator has been replaced, but my first job on checking these type of faults is to remove the alternator wires then check it next day.
Make sure nothing is switched on especially in the boot.

The car starts fine and drives but if left overnight it wont start. Central locking works and when you put the key in all the lights come on, when you try to turn it over it ticks loudly. I am getting the car tomorrow to try and fix it. The car has been jump started a couple of times.

Seems to point to a starter motor.....

Unless the ticking is the solanoid trying to turn the starter but not quite enough juice in the battery.

When the ignition is first turned on, the battery has to cope with all the ECUs starting up, the vehicle doing its self check, priming the fuel and finally giving enough ooomph for the starter and spark plugs, not always easy for a tired battery.

As already stated the problem is likely to be either a duff battery or something is discharging it overnight. The easiest way to check is to disconnect the battery at night, if it doesn't start in the morning that points to the battery being at fault, if it does then something is discharging it.

Remove the batt+ connection and connect it to one side of an ampmeter and connect the other lead to the battery, that will measure any current flowing, before doing this make sure everything is turned off and remove the meter before trying to start the car. A current of up to around 100ma is acceptable but much in excess of this will discharge the battery. Watch the meter for a few minutes as there could be something turning the ECU on.

Peter

peugeot30v6 wrote:The car starts fine and drives but if left overnight it wont start. Central locking works and when you put the key in all the lights come on, when you try to turn it over it ticks loudly. I am getting the car tomorrow to try and fix it. The car has been jump started a couple of times.

This sounds more like a battery problem.

Maybe it's a coincidence and the alternator went at the same time. Or maybe she went to one of these garages that fix faults by changing parts until it clears, starting with the most expensive.

I've got a 2005 S40, there was a lot of alternator failures on these, quite common.

Be careful jump-starting especially with a modern car with a smart alternator; it can put too much voltage across to the dead car and f*ck it up.

Changing the battery is fairly uneventful on these; the manual says to 'wait' 5 minutes after removing the key before you dis the battery. You will lose the time and audio settings (Bass/Treble etc) but nothing else.

The S40 electrics are not normally a problem so I doubt there will be a 'drain' somewhere.

My original Volvo battery lasted 9 years and towards the end it was slow to turn over and I was getting weird messages up on the MFD like POWER STEERING SERVICE and POWER SYSTEM SERVICE

I have got the car today and because it was bought brand new and driven by my 81 year old grandmother it only has 22000k for a 56 plate. She said she has never replaced the battery but when the she had the alternator problem the battery started playing up. It says on the service records that it was replaced. I will replace the battery tomorrow with a new one. Funny thing was she wanted to sell it because of this problem and the price she was told she could get was only £540 because of a electrical problem!!

Don't do what I did and leave the 'new' Battery in the boot.......

The boot opens with an electric latch and I'd already removed the car's battery

Got the car fixed today. Turned out to be a clip that was broken in the drivers door holding a switch down that was draining the battery overnight. The battery was also replaced because it had been drained so many times.

Can you tell me what/where it was for the record?