Some days it will be fine, then other days I get in the car and its
dead. The clock LCD is blank and I have to get a jump start. Once
running and given a little time to charge everything is fine.

Already tried disconnecting the boot interior bulb as thought it might
be staying on. Noticed the problem tends to happen in wet weather.
Also replaced a part in the alternator (cant remember the name of it)
something to do with voltage.

Any ideas what the problem could be??

benpost wrote:

Your first check is to make sure that's working.

Get a multimeter with a 20V or so scale. Connect is across the battery
terminals. You should see 12-12.5 volts or so. Less means the battery is
discahrged.

Start the car. It should now read at least 13.5 volts, hopefully a bit
more. Turn on the headlamps. and rev the engine gently a bit, then let
it idle. It should still read 13.5 or more. Less means the alternator
isn't charging.

Do those tests and post back.

If

"benpost" <olney_ben (AT) talktalk (DOT) net> wrote

Check fluid levels in the battery. Seriously low exposing plates allows for
growth to form between the plates acting as a high impedance short, thus
discharging the cell(s).

How old is the battery?
This could be a terminal issue, are they corrosion free and tight?

As a minimum the battery probably needs a real charge - car alternators with
short commutes do not recharge a battery. 24 hours on charge needed to do
this.

Open circuit voltage for a charged car battery is 12.5V With the car running
you would expect to see 13.6 Minimum.

Dave

"benpost" <olney_ben (AT) talktalk (DOT) net> wrote

Three options:

1) Someone's wired the radio up incorrectly. Not at all uncommon in the MK2
as the ignition switched live isn't obvious, so people wire both lives up to
the battery. This results in the radio draining the battery. There is a
switched ignition live behind the fusebox on CE2 (post 1990) cars, or you
can run one from the blower switch.

2) You have a car alarm fitted.

3) Your battery is dead.

I'd check them in that order, and expect to be buying a new battery before
winter. If it's been flat a few times it won't start the in frost.

I wouldn't be at all surprised if the battery is nearly dead now. Try
checking the voltage with a multimeter - charging with the engine running,
and after being fully charged and left overnight disconnected. If it's much
below 12.8V after being fully charged and left, it's dead. I also wouldn't
be at all surprised if the battery is never getting fully charged. Wickes
are clearing out their automotive range and are selling battery chargers at
around £3 a pop...

thanks for the responses... it was found to be the battery playing
up.. as a couple of times recently the car would not start, but
different to normal.

what happened was i'd turn the key and it would act like the battery
was dying, struggling to turn the engine, then 5 mins later all would
be fine. the alternator was not drawing any more than it should at
that point so battery was to blame. just got a new one fitted!