Battery problems now

Billy2Jags

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I'd guess you don't have a good connection to the battery?
Put a meter across the battery terminals to see where it's at.
 

GeoffR

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The stop start models use an AGM (Advanced Glass Matt) battery
AGM is Absorbed, or absorbent, Glass Mat. Absorbent because the electrolyte is absorbed into the glass mat and thus the battery is non-spillable.
 

macblack

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OK so they replaced the battery with a new one.

The guy asked me to try starting the engine and the same thing happened, air vents start to open, radio comes on, a few seconds later try to start the engine and nothing (not even an attempt). Few seconds later again, the screen switches off, vents close, radio off (all the lights on the dash are on fine).

So he tried to boost it, nothing happened and then he said he had the same issue with a land rover, he said to give a minute or two.

Waited, then tried it, engine started everything OK!! What the..

I put a voltmeter across the battery terminals and with the car on (but no engine running) the reading is the same as the last new battery 12.3v? When I start the car the voltage rises to 14.8?

I'm at a loss...
 

AntF

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Voltages look OK - 12.3v is a bit low but about right if the car is open and 'alive'. Looks like the alternator is charging too.

The brake pedal switch can become faulty that can cause the car not to start, as it thinks the pedal isn't being depressed. Are your brake lights working as this may give a clue. Try pressing the pedal really hard when trying to start to see if it changes. I think switches are not that expensive, but swapping out parts at random is not ideal, but you may get lucky. Have you read any fault codes from the car?
 

Jimbov8

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Agree with AntF, classic signs of a defective brake pedal switch.
 

macblack

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Voltages look OK - 12.3v is a bit low but about right if the car is open and 'alive'. Looks like the alternator is charging too.

The brake pedal switch can become faulty that can cause the car not to start, as it thinks the pedal isn't being depressed. Are your brake lights working as this may give a clue. Try pressing the pedal really hard when trying to start to see if it changes. I think switches are not that expensive, but swapping out parts at random is not ideal, but you may get lucky. Have you read any fault codes from the car?

Thanks guys this does make a lot of sense, I'll check it later today.
 

macblack

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I said earlier in the thread that both times the car failed to start the brake pedal was really stiff. I was just searching the forum and came across this:

12-06-14, 12:49
If you have sat in the car and been playing with the pedal it can pump up the servo to such a level that with normal pressure you can't get enough travel to activate the switch. Simply press really hard on the pedal to overcome this. In future don't sit with the engine off with your foot on the pedal. You aren't the first to do it and I doubt the last. I did this too early on in my ownership of my first XF.

Could that be the problem?
 

Jimbov8

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I said earlier in the thread that both times the car failed to start the brake pedal was really stiff. I was just searching the forum and came across this:

12-06-14, 12:49
If you have sat in the car and been playing with the pedal it can pump up the servo to such a level that with normal pressure you can't get enough travel to activate the switch. Simply press really hard on the pedal to overcome this. In future don't sit with the engine off with your foot on the pedal. You aren't the first to do it and I doubt the last. I did this too early on in my ownership of my first XF.

Could that be the problem?

It could be the problem if that’s what you’re doing.:mrgreen:
 

macblack

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I think it's one of those muscle memory things, but I always have my foot on the brake when I turn the car off..
 
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