Quote:
Originally Posted by grivas
What you have read there is 'residual' voltage, which is misleading, leave it to stand for an hour and you will find the battery is dead.
CHARGE the battery for 24 hours, then leave it disconnected for 1 hour then measure voltage, it should read at least 12.5V, start car and check voltage with engine running, should be 14.4V +, switch lights on, radio, demister and check again, should be near 13.8v any significantly lower readings, need a new battery, and your alternator is probably in need of attention, new regulator pack?. Good luck.
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Thank you.
Just to clarify, with engine running the terminal readings are 13.8v.
With battery disconnected after an hour it reads 12.3v. With battery connected to car and a spare battery attached in parallel it reads 12.6v. the increase in voltage makes no difference to the cranking time before the engine will run.
With the engine ticking over there's 13.8v. with headlights on it's still 13.8v. add rear screen demister it's 13.7v and adding climate control it's down to 13.6v and that at tick over speed.
With revs increased to 1800 rpm I've turned everything on and the voltage is steady at 13.8v
That's lower than I'd like and probably indicative of the alternator but not necessarily the starting problem.
I just tried an inline amperage test. There is a current draw of 0.34 amps. So I'm currently ( no pun intended) pulling fuses.
Under bonnet fuse box:
F8 removed value drops to .29a. with fuse back in and disconnecting the connectors on top of diesel heater the value drops to .14a. cleaning and reconnecting it remain at .14a. so still have a .14 current draw. Current draw is now .02a. I can deal with that.