Battery issue?

SamsterGTi · 14th March 2015, 20:00

Hey all,

I'm having a car battery issue and just wanted to describe the symptoms and see if it means anything to anyone.
Diesel mk2 ZT, quite a few times this last 10 days the car battery has been flat enough to not allow the starter to crank.
No big deal, jumping it of another one if my cars till I get round to fitting a new one.
However, today I noticed that when it is "flat" and I crank the engine, the headlights come on?
The switch is off, however it only does it when the battery is too low to crank the engine.
Is this a clever install or a weird short somewhere?
Once the battery is charged enough to crank and start the car the headlights do not come on.

Thanks for reading,

Sam.

klarzy · 14th March 2015, 20:05

Quote:

Originally Posted by SamsterGTi

Hey all,

I'm having a car battery issue and just wanted to describe the symptoms and see if it means anything to anyone.
Diesel mk2 ZT, quite a few times this last 10 days the car battery has been flat enough to not allow the starter to crank.
No big deal, jumping it of another one if my cars till I get round to fitting a new one.
However, today I noticed that when it is "flat" and I crank the engine, the headlights come on?
The switch is off, however it only does it when the battery is too low to crank the engine.
Is this a clever install or a weird short somewhere?
Once the battery is charged enough to crank and start the car the headlights do not come on.

Thanks for reading,

Sam.

the lights flash to tell you the battery is flat and may result in the electronics failing..

general rule is lights flash, don't crank until charged..

when you do get the engine running check you have 14-14.5V at the terminals to make sure the alternator is working properly...

then check all peripherals shut down when you lock the car... sat nav, hiline etc..

SamsterGTi · 14th March 2015, 20:11

Spot on, many thanks.
Thought the headlight thing might be a clever sign.
I always shut everything down whilst engine is running before switching off.
Everything else works, unlock, glow plug light goes out.
Sometimes he cranks for 1 or 1.5 seconds and then the starter clicks as per.
New battery will be sourced Monday, hope it cures it and I don't have some short somewhere.

Sam.

klarzy · 14th March 2015, 20:14

Quote:

Originally Posted by SamsterGTi

Spot on, many thanks.
Thought the headlight thing might be a clever sign.
I always shut everything down whilst engine is running before switching off.
Everything else works, unlock, glow plug light goes out.
Sometimes he cranks for 1 or 1.5 seconds and then the starter clicks as per.
New battery will be sourced Monday, hope it cures it and I don't have some short somewhere.

Sam.

check the charge voltage first, it may just be a loose connection or a 20 quid set of brushes...

things like sat nav drive etc can stay on and drain the battery without you knowing so if you have one check it powers down properly and the drive light goes out

SamsterGTi · 14th March 2015, 20:23

Good idea, will put multi meter straight on him tomorrow.

There is no stereo fitted at the minute, no after market lights or anything. Air con and any lights get switched off before shutting engine down.
Trying to see if there is a pattern when it happens. Like leaving it unlocked whilst working on it, then locking it and leaving it overnight.
Once it's running he's great, no issues just that odd "first" start of the day.

Sam.

raykay · 14th March 2015, 20:26

It's the Light Switch Module emergency backup system, one way it is triggered is by the low battery voltage. It switches on the dipped headlights and tail lights and inhibits the other lights except the brake lights.

Trying the starter motor with a low battery pulses the solenoid on and off as long as the key is turned to 'Start', due to the voltage drop through the starter motor. When it is 'on' (and trying to operate the starter motor), it reduces the voltage enough for the LSM to operate its emergency mode - switching on the head & tail lights. When it is 'off' the voltage rises sufficient to allow the LSM to return to normal and the lights go out - giving the 'flashing headlight 'syndrome.

SamsterGTi · 14th March 2015, 20:39

Cheers Raykay,

Yeah I understand that now, clever system.
Upsets me the more I learn about how good these cars are that they didn't save the British car industry.

Anyhow, hopefully it's just an ageing car battery.

Cheers,

Sam.

Kev75 · 15th March 2015, 07:03

There's a post in the tec section by BigRuss about headlights flashing when cranking! Have a read.

Kev

SD1too · 15th March 2015, 11:55

Quote:

Originally Posted by SamsterGTi

Anyhow, hopefully it's just an ageing car battery.

Sam,

The most likely reason is that your journey pattern is not providing sufficient time for the alternator fully to charge the battery. Is the car used regularly for long journeys?

As you've allowed your battery to become discharged for "quite a few times" over 10 days, it may be beyond recovery, but it's a good idea to attempt resuscitation by investing in a smart charger such as those made by CTek (as I have done, recommended!).

A car battery which is kept fully charged at all times will last a very long time.

Simon

SamsterGTi · 15th March 2015, 18:12

Hi Simon.

True, I have performed some short journeys but he's mainly used to do motorway journeys of an hour or more.
No worries, I'll put a new battery on if it persists.

14th March 2015, 20:00	#1
SamsterGTi Regular poster MG ZT cdti Join Date: Feb 2015 Location: Kettering Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Battery issue? Hey all, I'm having a car battery issue and just wanted to describe the symptoms and see if it means anything to anyone. Diesel mk2 ZT, quite a few times this last 10 days the car battery has been flat enough to not allow the starter to crank. No big deal, jumping it of another one if my cars till I get round to fitting a new one. However, today I noticed that when it is "flat" and I crank the engine, the headlights come on? The switch is off, however it only does it when the battery is too low to crank the engine. Is this a clever install or a weird short somewhere? Once the battery is charged enough to crank and start the car the headlights do not come on. Thanks for reading, Sam.

14th March 2015, 20:26	#6
raykay I really should get out more....... Now Other Manufacturer Join Date: Nov 2006 Location: Co. Kerry Posts: 2,786 Thanks: 16 Thanked 310 Times in 283 Posts	It's the Light Switch Module emergency backup system, one way it is triggered is by the low battery voltage. It switches on the dipped headlights and tail lights and inhibits the other lights except the brake lights. Trying the starter motor with a low battery pulses the solenoid on and off as long as the key is turned to 'Start', due to the voltage drop through the starter motor. When it is 'on' (and trying to operate the starter motor), it reduces the voltage enough for the LSM to operate its emergency mode - switching on the head & tail lights. When it is 'off' the voltage rises sufficient to allow the LSM to return to normal and the lights go out - giving the 'flashing headlight 'syndrome. Last edited by raykay; 14th March 2015 at 20:42..

15th March 2015, 07:03	#8
Kev75 Avid contributor Rover 75 Saloon Join Date: Apr 2012 Location: Nantwich Posts: 151 Thanks: 260 Thanked 41 Times in 34 Posts	Flat battery There's a post in the tec section by BigRuss about headlights flashing when cranking! Have a read. Kev

14th March 2015, 20:11	#3
SamsterGTi Regular poster MG ZT cdti Join Date: Feb 2015 Location: Kettering Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Spot on, many thanks. Thought the headlight thing might be a clever sign. I always shut everything down whilst engine is running before switching off. Everything else works, unlock, glow plug light goes out. Sometimes he cranks for 1 or 1.5 seconds and then the starter clicks as per. New battery will be sourced Monday, hope it cures it and I don't have some short somewhere. Sam.

14th March 2015, 20:23	#5
SamsterGTi Regular poster MG ZT cdti Join Date: Feb 2015 Location: Kettering Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Good idea, will put multi meter straight on him tomorrow. There is no stereo fitted at the minute, no after market lights or anything. Air con and any lights get switched off before shutting engine down. Trying to see if there is a pattern when it happens. Like leaving it unlocked whilst working on it, then locking it and leaving it overnight. Once it's running he's great, no issues just that odd "first" start of the day. Sam.

14th March 2015, 20:39	#7
SamsterGTi Regular poster MG ZT cdti Join Date: Feb 2015 Location: Kettering Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Cheers Raykay, Yeah I understand that now, clever system. Upsets me the more I learn about how good these cars are that they didn't save the British car industry. Anyhow, hopefully it's just an ageing car battery. Cheers, Sam.

15th March 2015, 18:12	#10
SamsterGTi Regular poster MG ZT cdti Join Date: Feb 2015 Location: Kettering Posts: 42 Thanks: 0 Thanked 4 Times in 4 Posts	Hi Simon. True, I have performed some short journeys but he's mainly used to do motorway journeys of an hour or more. No worries, I'll put a new battery on if it persists.