Battery light not on when engine is off - car won’t start

[HazzaCrawf]

Hi all,

Just a problem with my car that I’d like to get a second opinion on.

When turning the ignition on, the battery light does not illuminate like it should. The engine will try to crank but won’t start. That suggests a dead battery, however the battery voltage when tested with a multimeter is OK. Any ideas of where to look next? The car has been sat for 3 weeks.

Car is a 2005 Clio. About to get rid of it - at my wits’ end!

Thanks in advance

[Stuart M 1976]

It it's cranking over it can't be a flat battery. Immobilized issue maybe?

[lord trumpton]

HazzaCrawf said:

Hi all,

Just a problem with my car that I’d like to get a second opinion on.

When turning the ignition on, the battery light does not illuminate like it should. The engine will try to crank but won’t start. That suggests a dead battery, however the battery voltage when tested with a multimeter is OK. Any ideas of where to look next? The car has been sat for 3 weeks.

Car is a 2005 Clio. About to get rid of it - at my wits’ end!

Thanks in advance

When you say 'try' to crank do you mean it's cranking properly or not?

If the battery is knackered then the voltage reading alone is not an indicator. It's the amperage that turns the car over

Try and jump start it if you have leads

[ford2210]

Providing your battery is good like you say, Shut all the doors, hold the lock button in the centre of the dash for 15 secs, you may or may not get an audible noise at 15secs. Then unlock/lock/unlock with the fob and it should start.

[mickthemechanic]

Hi


Does the engine management light come on when the ignition is turned on?

[HazzaCrawf]

lord trumpton said:

HazzaCrawf said:

Hi all,

Just a problem with my car that I’d like to get a second opinion on.

When turning the ignition on, the battery light does not illuminate like it should. The engine will try to crank but won’t start. That suggests a dead battery, however the battery voltage when tested with a multimeter is OK. Any ideas of where to look next? The car has been sat for 3 weeks.

Car is a 2005 Clio. About to get rid of it - at my wits’ end!

Thanks in advance

When you say 'try' to crank do you mean it's cranking properly or not?

If the battery is knackered then the voltage reading alone is not an indicator. It's the amperage that turns the car over

Try and jump start it if you have leads

Sorry - wasn’t clear enough. The engine turns over but struggles to start. Even then, the battery light doesn’t illuminate when the engine isn’t running.

Also, having just bump-started it as a last resort, the battery/no charge warning light comes on above 2000rpm, and car doesn’t restart. Faulty alternator?

[HazzaCrawf]

mickthemechanic said:

Hi


Does the engine management light come on when the ignition is turned on?

Nope, no engine light at all.

[stevieturbo]

Have you just bought it or something ?

Sounds like a plethora of problems.

[HazzaCrawf]

stevieturbo said:

Have you just bought it or something ?

Sounds like a plethora of problems.

Had it for three years. The last year it’s been a bottomless pit!

[BrassMan]

Battery has already been suggested, so:

You have a spark? Pull a plug lead off and get someone else to turn it over, a little spark should be visible.

All fuses okay? I manged to blow my engine management fuse while checking the power supply to my reversing lights recently.

Fuel getting through?

[Penelope Stopit]

HazzaCrawf said:

Sorry - wasn’t clear enough. The engine turns over but struggles to start. Even then, the battery light doesn’t illuminate when the engine isn’t running.

Also, having just bump-started it as a last resort, the battery/no charge warning light comes on above 2000rpm, and car doesn’t restart. Faulty alternator?

Warning light coming on at 2000 RPM could be down to worn alternator brushes. While looking at the alternator warning light crank the engine for a split second several times so that the alternator is being turned a little at a time, you may well see the warning light come on dimly when the alternators rotor/slip-ring is in a certain position, if the light does come on this proves the brushes are at fault and the alternator won't be charging the battery

[HazzaCrawf]

Penelope Stopit said:

HazzaCrawf said:

Sorry - wasn’t clear enough. The engine turns over but struggles to start. Even then, the battery light doesn’t illuminate when the engine isn’t running.

Also, having just bump-started it as a last resort, the battery/no charge warning light comes on above 2000rpm, and car doesn’t restart. Faulty alternator?

Warning light coming on at 2000 RPM could be down to worn alternator brushes. While looking at the alternator warning light crank the engine for a split second several times so that the alternator is being turned a little at a time, you may well see the warning light come on dimly when the alternators rotor/slip-ring is in a certain position, if the light does come on this proves the brushes are at fault and the alternator won't be charging the battery

Brilliant, thank you. According to the Haynes, the light not illuminating while the engine is off further points towards the alternator.

Thanks

[TooMany2cvs]

The "battery light" is not a battery light. It's telling you nothing about the battery at all. What it's telling you is that there is no charge being generated.

If it's not coming on at all with the ignition on, but engine not running, then there's no field excitation getting to the alternator, to "turn it on". On an older car, it might be that the bulb has blown - with it failed, no current is passing through. On something more modern, it'd be ECU controlled, so it's more likely to be an ECU problem, or just the ignition switch itself.

[Penelope Stopit]

HazzaCrawf said:

Brilliant, thank you. According to the Haynes, the light not illuminating while the engine is off further points towards the alternator.

Thanks

Yes it can do but there are other things that can stop the light from working such as a blown bulb, fuse or broken wires to the warning light.
You can check the warning light circuit by switching the ignition on (not starting the engine), disconnecting its wire from the alternator and connecting it to a good earth, the light should illuminate at full brightness

[Penelope Stopit]

TooMany2cvs said:

The "battery light" is not a battery light. It's telling you nothing about the battery at all. What it's telling you is that there is no charge being generated.

If it's not coming on at all with the ignition on, but engine not running, then there's no field excitation getting to the alternator, to "turn it on". On an older car, it might be that the bulb has blown - with it failed, no current is passing through. On something more modern, it'd be ECU controlled, so it's more likely to be an ECU problem, or just the ignition switch itself.

The light not being on doesn't always mean there is no charge, a blown bulb, fuse or faulty wiring in the warning light circuit doesn't always mean there is no charge
There is residual magnetism at the rotor and many alternators are self exciting but do need the engine revs to be upped to around 3000 RPM to cut-in and charge, once they have cut-in they will remain in a charing state even if those revs are now lowered to tick over

Hence an alternator warning light not working as it should often fools people when they are testing a charging circuit

[Stiggolas]

Worth checking the engine earth strap at the gearbox end, they are known for corroding and causing starting issues. If there's no earth, you will get no lights etc. Took me a while to sort ours, but ran faultlessly for 2 more years after that.

[Penelope Stopit]

Stiggolas said:

Worth checking the engine earth strap at the gearbox end, they are known for corroding and causing starting issues. If there's no earth, you will get no lights etc. Took me a while to sort ours, but ran faultlessly for 2 more years after that.

Good point, I advised on everything but the obvious

I best add this - The voltage at the battery needs to be measured when cranking so that it is under load, connecting a meter across it without a load on it tells you very little about its capacity, you could also measure the voltage at the starter when it's cranking but need to mind your hands don't get cut to shreds on moving parts

[HazzaCrawf]

Cheers for all your input, guys. My confusion with the source of the fault is this:

How can a dead alternator prevent the car from starting, bearing in mind that the battery is fully charged, and the starter is functioning normally? A non-functioning alternator could prevent the battery from being charged, but this would present a problem once the engine was started and battery power was being used, I imagine?

Is there any part of the alternator that could, if corroded/degraded/eaten by a mouse, prevent the car from starting regardless of battery condition AND disable the no-charge light while the engine is off? The light appears to be working properly as it appears intermittently at high RPMs.

Please forgive me - I’m handy with spanners but electrical problems are new to me.

[TooMany2cvs]

HazzaCrawf said:

How can a dead alternator prevent the car from starting

It won't.

[Penelope Stopit]

Penelope Stopit said:

Stiggolas said:

Worth checking the engine earth strap at the gearbox end, they are known for corroding and causing starting issues. If there's no earth, you will get no lights etc. Took me a while to sort ours, but ran faultlessly for 2 more years after that.

Good point, I advised on everything but the obvious

I best add this - The voltage at the battery needs to be measured when cranking so that it is under load, connecting a meter across it without a load on it tells you very little about its capacity, you could also measure the voltage at the starter when it's cranking but need to mind your hands don't get cut to shreds on moving parts

This from Stiggolas plus check voltage when under load