Flat battery

K

keith777

Member
My Z4 is a weekender, 8 weeks ago went to it and battery was flat, bought new battery and all was well - until now.
Tried it today after no use for 2 weeks - dead ! Jump started it and went for a 30 mile run, got back switched engine off outside garage opened up got back in car - nothing dead as a dodo ! Jump started again & when I revved it various lights on dash would flicker and radio would go off and come back on !
Tried voltage tester in ciggy lighter showed 8v then 13.2 when engine was running could it be the alternator ?
By the way it's a 2. 0 so waiting for the told you so's should've got a 6 pot .
Hate it when my cars not running right - help !
Cheers Keith.
 
Output may be a little low so try measuring at the battery. I'd not expect the car to last 2 weeks without running though, pretty normal.
 
You need the battery charged and engine idling for a few minutes then get a voltmeter on the battery terminals with the engine OFF looking for a min 12.4 Volts. Anything below this indicates a battery or charging system problem.
If the battery volts are OK, then with the engine IDLING and all accessories OFF test the alternator by measuring the volts over battery terminals again, a healthy alternator should now be reading between and +.5 and +2 volts above the static test reading. Less than an extra +.5v indicates an undercharging alternator, over +2v it's overcharging and needs service or replacement.
Then do a running load test now with the engine at a steady 2000 RPM with all accessories on, (lights, radio, rear window/seat heaters etc) you should still get a reading of at least .5v above the static base reading.

Once you have done that and things look OK I'd suspect loose or poorly grounded battery connections/earths or even the battery Safety Terminal or cable run and block connectors http://www.z4-forum.com/forum/viewtopic.php?t=13765

Good luck and let us know how :thumbsup: you get on
 
Quick update, jump started again tonight checked voltage at battery between 12 and 14v so think battery is goosed ! 3 months old !! That's halfords for you !!
 
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