Battery draining

[crazymatelot]

Guys, need suggestions as to what could be causing my battery to drain. If I leave the car overnight it is okay and will start the next day, if I leave it two days, it will not start, even though I have an optimiser on the battery. I took it to my local college today for the the lads and instructors at the engineering section to give it a look over to solve the problem. They tried everything, but were unable to come up with the solution. They did, however tell me that something is pulling 0.3amps constantly. We tried disconnecting the alternator, in case it was the regulator or a dicky diode, no luck, we pulled every fuse and relay in turn, no luck. MY car is a 1998 4.2 and according to the handbook I downloaded, the clock is powered by fuse no 10 however pulling same fuse does not cut off the clock, so it may be a previous owner has rewired some of it, or handbook is wrong. The only place I can think of where the amps may be escaping is somewhere in the dash/radio. Has anybody else experienced this or got any suggestions.

[JensenA]

IIRC there was another thread on this topic, another constant drain on the battery is the car alarm. Cerb's do need a good quality battery though - the Optima Red top seems to be getting good reviews.

Edited to Add..found the other thread

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Edited by JensenA on Thursday 10th April 15:17

[sonnylad]

Worth checking boot light switch, when my switch packed up and with the lamp on constantly thats all it took to drain battery over a couple of days.

Russ

[mwillett]

Hi,

I have a Cerbera 4.2 2000 and have the same problem - here's the advice I've been given (which I'll be trying this weekend).

1) Check for boot light being left on.
(either use a digtial camera with a delayed shutter release to check or lock your child in the boot)

2) With engine off, measure voltage across battery should be 12v- 13v

3) With engine on, measure voltage across battery should be 13v - 14v

4) If these are, pull out interior light bulb and measure amps across terminals
should be 1A - 1.5A

Not sure what to do if this yields odd results - but guess I'll be asking for help again.

[sonnylad]

If boot light is staying on it can sometimes just be visible at night illuminating number plate.

[thegreengoblet]

sonnylad said:

If boot light is staying on it can sometimes just be visible at night illuminating number plate.

One of my cabin interior ones was on for a few days once. Only noticed cause I looked out late one night. Must of been right on the toggle point and a possible door slam flicked it over.

[crazymatelot]

sonnylad said:

If boot light is staying on it can sometimes just be visible at night illuminating number plate.

It is definately not the boot light, we manually held the boot light off, when checking the drain amps, and also checked all other internal lights were off. This is a real enigma. With regard to the Alarm/Imobiliser, it should not be using 0.3 amp unless it is defective. But, again checked drainage amps with alarm on and off and with imobiliser on/off.

[Nickccc]

I had this, took ages to work out.
It was the boot light, open the boot look on the left hand side at the back corner you will see a small black switch, it has a pluenger coming out of the bottom, when the boot closes this plunger is pulled away from the switch body, mine had snapped off leaving the boot light on, which then flattened my battery, the alarm going off for no reason is also due to this, good luck.

[jbvipercerb]

I've seen a fair few cars going flat over a day or two and most of the time its the battery on its last legs.
The next biggest problem, if you have checked there are no lights on is the radio being faulty (it will work ok but drain the battery), try unpluging it and see if it helps.
The next item to drain a battery is the alternator, try disconnecting it, or the big fuse to isolate it. Hope this helps.