Electrics: Battery goes flat after standing a week or so

[KJR]

My battery regularly goes flat after standing a week or so, it is a new battery and I put problem down to the car being used very little(at times). This week after standing for a week or so it started (just) and I decided to have the alternator etc checked at a Bosch auto electrics place. Battery and alternator are fine but there is something which at times consumes a small current when the car is asleep. Evidently this is in the circuit with the central locking and courtesy lights, I believe one of the cars electronic modules(possibly the upper) is also in this circuit. I note in this forum s60´s seem to dislike being left unused for a period of time and flatten their batteries and I see today a V50 also left its owner stranded last year after only 2 weeks resting. Do any of you kind people have any suggestions as to what might be consuming power on my car or is there a known fault? I should point out my alarm back up batteries went flat around 4 years ago and I never replaced the siren unit I simply lock with the key and unlock with remote and the passenger central locking module works but at times makes the brrr noise which presents itself when the motor is on its way out, the Bosch guy doesn´t think either of these contribute to the problem but does anybody know any differently? Sorry for rambling again!

[grass hopper]

did bosch auto electrics give the current draw reading? these cars can take up to 15 mins for all the modules to go to "sleep" then take a reading,should be down to 0.03 amp current draw if all ok,if higher there can be high current draw if the alarm siren is faulty but this usually posts a fault code,worth putting the back seats down and look in the boot area to make sure the courtousy lights are going out,the only other way is to pull out fuses one at a time to see which circuit is causing the current draw.

[KJR]

The reading at the time I looked with the Bosch guy was down to 0.025-0.03 amps but he said at times it was at this and at others it went up to 0.3/ 0.4. He did mention there was a fault code with the alarm but I assumed this was to do with the flat batteries in the siren, the boot lights are definately off. The alarm sounds like a suspect but I find this odd as I don´t arm it.

[grass hopper]

Originally Posted by KJR

The reading at the time I looked with the Bosch guy was down to 0.025-0.03 amps but he said at times it was at this and at others it went up to 0.3/ 0.4. He did mention there was a fault code with the alarm but I assumed this was to do with the flat batteries in the siren, the boot lights are definately off. The alarm sounds like a suspect but I find this odd as I don´t arm it.

it will be the siren,even without "arming" the other modules will continually try to comunicate with the faulty siren and flatten the battery,i have had this fault before,worth replacing the siren as its good to be working if required ! and nothing lost if it does not fix,but i think it should.

[GSMGuy]

If it's the Std alarm, it will automatically arm when you lock the car - If it has a faulty siren (common) then it may be drawing excess current, trying to recharege the internal batteries, which could be faulty...

Mike

[grass hopper]

Originally Posted by GSMGuy

If it's the Std alarm, it will automatically arm when you lock the car - If it has a faulty siren (common) then it may be drawing excess current, trying to recharege the internal batteries, which could be faulty...

Mike

my last fault with this was not flat battery in the siren, but no communication on the network with the siren,basically the can network had high curerent draw trying to find the siren module.

[KJR]

Mike, I don´t think the alarm arms when I lock it with the key because the light on the dashboard does not flash, but I think you are right about it draining current to try and recharge the alarm batteries...Grass Hopper, I think you also have a point about it trying to locate the siren module. The batteries of the siren must be completely flat now as they originally showed signs of failing at least 4 years ago, so I doubt there is any communication from it. When you experienced this problem(the communication problem) did your car battery go flat as well? If so, how long did the car stand before it went flat? Looks like a new siren unit is necessary. Thanks to you both.

[grass hopper]

Hi mike,while the amp gauge is showing the current draw,as mentioned allow 15 mins for the modules to settle then if the current is still high remove the fuse for the siren,think this is in the side of the dash,and the current will drop straight away,if it drops replace the siren,

a previous car i had like this would flatten the battery in about 5 days if not used at all.

[agallo]

Hi there,

This thread is of interest to me as I too am having a similar issue. Unfortunately the current drain isn't in the .02-.03 or .2-.3 range - but in the 3.84 amp range! I don't quite understand why such a drain! I let the car 'go to sleep', giving it at least 15 minutes. I then, with my voltmeter in series, measure the current drain. It's always exactly at 3.84 amperes. I thought that perhaps my voltmeter was in error - it 's an inferior brand. So I purchased another VM - same reading.
I've purchased a battery charger. With the two red leads tied in (closed circuit) the charger reads an 8 amp pull. If I remove the two red leads (undue the screw and remove the read leads) open circuit, then the charger reads 5-6 amps. And the battery charges properly.
I've replaced the battery.
I've gone through the exercise of removing all the fuses, one by one, and checking if the drain stops. No go. I thought, for a while, that I had the issue resolved when I replaced a defective fan blower. But no go - the issue still remains.
Any help would be trully appreciated.

Kind regards,
Angelo

[BobS]

Hi,

Check your alternator. It is most likely a diode has gone. The alternator has a permanent live feed direct from the battery. Disconnect battery then the alternator feed and check current consumption. Don't start engine without reconnecting the power feed!

Hope this helps?
Bob