Also the battery may be getting old and yes batteries do decay over time - SULFATION I recently replaced my battery as I had noticed that the car was getting sluggish when turning over. If your battery has passed it, I would fit the biggest battery for the GT, mine has a CCA of 620amps. Please read the following website page, I found it very informative, Car Battery Testing

CCA - Cold Cranking Amps

 

engine off, 12.6v. charged or flat doesn't make much difference.

ticking over, at least 14v if the only load is the engine management system and the battery.

 

engine off, 12.6v. charged or flat doesn't make much difference.

There is a difference between charged & flat.
12.6V (or slightly higher) = charged
12.2V = Flat

Between 12.2V & 12.6V = Needs charging.

If you are seeing around 10V, then a cell in the battery has failed and it needs replacing, charging won't bring it back. 100% warranty replacement if still covered.

 

Thanks for the input all.

Another strange thing...and I've have this happen to me before on my Sportwagon

I'll get in and try to start, it'll turn over slowly and eventually give up. I'll then make sure everything is 'off' ( lights / radio etc. ).
Re-try and it'l go click click click sound that could be the starter motor.

Now the interesting / weird bit. If I then try to jump start it, when I connect the cables ( with SW ignition 'Off' )
there will be a very big spark when I connect the cables and the engine will turn over once or twice.

The cables will get very hot - so the battery is obviously under load.

I disconnect the cable sharpish - and the only way I can proceed is to disconnect the SW battery terminals completely and then use a charger on the battery for a few hours ( thereby giving up on the jump start ).

This was the scenario with the GT this morning - tried to jump start, GT battery under heavy load, wires getting hot,
me abandoning the jump start and getting the RAC to visit - ( hopefully they can monitor the battery health / charge health etc. ).

WHAT CAUSES THIS INABILITY TO JUMO START THE CAR?

cheers again!

 

What cables are you using, and where are you attaching them? If they're getting hot it sounds like they're under-sized for the current draw...

 

a discharged battery consumes electric, make sure the car providing the jump has a running engine and keep the jump leads connected for a few minutes before trying to start. but the cables shouldn't get hot, luke warm at the most. if they do get warm, they are too small and this won't help with the jump starting either.

 

places like quick fit and halfords should be able to do a free test on battery.....they pop a gauge between terminals
the cold really as an affect on batteries....my dad who was a mechanic allways said itll find the weak ones

 

The cables are what I'd call 'intermediate', as opposed to 'professional' or ' shlt'. My point being that there seems to be a higher than normal draw on the battery - and what would cause this ( what with ignition being off )?

 

could be the alternator itself, if a diode from the rectifier has blown. a midtronics tester can find this. most garages will have one, brand dealerships without question. we've got 4 tester like this, 2 older ones without printer, 2 newer ones with.

 

12.7 --- they're in heaven.
12.5 --- they're still alive.
12.2 --- there's lots to do.
10.8 --- is far too late.

Strictly speaking this only applies if the battery has not been charged or discharged for twenty four hours.

Did you mean that the SW starts cranking when you connect the jump leads?

 

yes...most strange as the sw ignition was off

 

Starter solenoid must have stuck on.