[thepartworntyreshop]

Hi all
Got a bit of a strange one here. On one of my P38s I seem to get a battery drain, well that's what I first thought, as when I was going out to start her (every 3 to 4 days) in the mornings I was getting the fault message "gearbox fault" coming up, so i'd hook her up to a spare battery i've got, heavy duty jump leads & robert's ya fathers brother but the plot thickens! I fully charged the battery the other day while still on the ol girl & went out in the morning with no problems, then jumped back in her in the afternoon & it happend again? So I tested the battery/alternator etc & the battery was reading 14.5 so maximum output but when I put the lights on there was no drop what so ever? & when I revved the engine nothing, stayed at 14.5? Any help? Could this be a starter motor issue that just happens when it feels like it? or could there be something else lurking around the corner I don't know about?
How help greatly appreciated guys

 

[Datatek]

Hi all
Got a bit of a strange one here. On one of my P38s I seem to get a battery drain, well that's what I first thought, as when I was going out to start her (every 3 to 4 days) in the mornings I was getting the fault message "gearbox fault" coming up, so i'd hook her up to a spare battery i've got, heavy duty jump leads & robert's ya fathers brother but the plot thickens! I fully charged the battery the other day while still on the ol girl & went out in the morning with no problems, then jumped back in her in the afternoon & it happend again? So I tested the battery/alternator etc & the battery was reading 14.5 so maximum output but when I put the lights on there was no drop what so ever? & when I revved the engine nothing, stayed at 14.5? Any help? Could this be a starter motor issue that just happens when it feels like it? or could there be something else lurking around the corner I don't know about?
How help greatly appreciated guys

14.5 Volts is a tad high, if the alternator has sufficient output to meet the load, the voltage will not drop.
I suspect that with the cold weather, the battery voltage is dropping when left for your 3 or 4 days. The cold always finds a fading battery.

 

[thepartworntyreshop]

Do you reckon that is all it might be Keith? As just a little worried that's all

 

[Datatek]

Do you reckon that is all it might be Keith? As just a little worried that's all

That would certainly be my guess, check the battery voltage before you start it after your 3/4 days, then get the missus to crank it and see what the voltage drops to, I've seen them show 12.5volts then drop to below 9 volts on cranking.

 

[thepartworntyreshop]

Cheers Keith i'll give that a go

 

[davidg]

If you are concerned about battery drain then do a couple of simple checks, make sure the becm is going to sleep correctly by opening the drivers door, leave key in ignition (not in ign or aux position),switch off all lights (including interior lights). When becm goes to sleep the "key in message" on message centre will disappear after 2 mins . If it does not disappear that is bad news because it means the battery will be discharging at a rate of ~2amps instead of the usual max of 40mA.
The other check to do is to check the installation of aftermarket fit items like telephone chargers, It's common practice for these to be wired into permantly live wires and this will flatten your battery after a couple of days.

 

[Datatek]

If you are concerned about battery drain then do a couple of simple checks, make sure the becm is going to sleep correctly by opening the drivers door, leave key in ignition (not in ign or aux position),switch off all lights (including interior lights). When becm goes to sleep the "key in message" on message centre will disappear after 2 mins . If it does not disappear that is bad news because it means the battery will be discharging at a rate of ~2amps instead of the usual max of 40mA.
The other check to do is to check the installation of aftermarket fit items like telephone chargers, It's common practice for these to be wired into permantly live wires and this will flatten your battery after a couple of days.

If the BECM is not going to sleep, the battery will be totally flat in a lot less than 3 days.