Battery keeps going flat?

[Splinter]

another electrical problem come from out of the blue with the mk3. 

When leaving the car for a few hours the battery goes flat. Battery & alternator fine.

Nothing to do with my stereo system, and disconnected everything to make sure.

The ex-£400 foxguard alarm system that's been on the car a few years packed up a few weeks ago. Had to do a bit of basic re-wiring under the dash to ignition to get round the immobiliser on the alarm,(good alarm! took 2 minutes!) but was okay for weeks afterwards.

However went to set off for work one day and battery dead and keeps going flat. I've now completley disconnected alarm from any power. What else could it be? Central locking? Bad Earth? Do I need to remove one fuse every night till I find the problem! or what could it be before I spend hours checking it all out. Doesn't matter if I lock it or not, still same problem. Also had front bumper removed, then moved car 4ward and drove on/pulled out ambient temp sensor from somewhere on wire loom, where's this go back??!!

After I moved the car, battery was okay for a few days, but then after started engine, few hours later = flat battery - problem had come back? so it is intermittent.

[Rain]

does sound like a duff battery but really need to check that something isnt draining it best way is with one of them screw drivers with a bulb in disconnect the battery and bridge the connection with the screw driver if the light comes on you got a drain normally an alarm will make it flash dimly not bright.

if its bright then you need to test the individual fuses see where its coming from but before you do check the boot light

[Splinter]

I'll try tonight as I've not been using it the last couple of weeks. Something is definitely draining it, and its nothing obvious like stereo or courtesy lights.. The battery is brand new and working fine.

[rubjonny]

Boot light?  Common one

[Splinter]

I aint got a boot light fitted!

[tobz.]

Try as rain said disconnect your battery and put a 12v bulb or even better a multimeter on the dc current setting between the terminal and disconnected lead. If you are drawing current with everything off then something isn't right. Start by removing each fuse one at a time checking to see if the current stops flowing after each one. If the current stops you can at least identify which circuit is at fault. If the fuses don't show anything up then repeat the process with all the relays. I've had this problem on a mk2 in the past and it turned out to be a sticking ignition relay. Even without the key in the ignition it was drawing 10amps!!! Could explain why it is intermittent aswell if the relay doesn't always stick.

[Rain]

another way you could be loosing charge is through a faulty earth strap but normally this leads to major loss of power when driving can be intermittant had this in the past where the earth lead to the engine was loose and making a poor connection battery wouldnt charge when driving or if it did not alot so it works in reverse the more you drive the less power your battery will have when you get back.

removing the earth straps spraying with wd40 and a wire brush on them to clean them up then dry and grease them before replacing them works best.

[fastphil]

sometimes the alternator can ground to earth if faulty,if none of the above methods work try disconnecting it to see if the amperage drain stops

[the_GTI_new_guy]

Even without the key in the ignition it was drawing 10amps!!!

At least it was keeping your wires warm then