Hard to find current drain

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Rompingdog

Rompingdog

New Member
Posts
7
Location
Derbyshire
I am having a problem with my P38 diesel at the minute with a wierd hard to track down current drain.
When I go to start the thing up, two turns and then nowt! Stick the jump leads on and apart from the usual two or three half hearted tries at firing up, away she goes.
Leave it overnight and then the following day, same thing. A couple of slow turns and then bugger all.
Battery is brand new from the car parts shop and is the right type. It has been tested as I took it back thinking it was kaput, but it is OK. Allegedly!!
So, has anyone any ideas what the problem might be?
If I stick a voltmeter across the battery terminals when the thing is running, I have 13.5 volts showing with all ancilliaries on, rear screen heater, front screen heater, fan, fog lights, full beam, indicators, radio etc so the alternator appears to be doing its stuff.
Switch the engine off and then the voltage starts to creep down until after about an hour or so, the voltage across the terminals is around 11.8 volts and dropping slowly.
Iv'e tried putting the meter on amps in series with the negative leg of the battery and the disconnected lead to see what is happening but apart from 2 or 3 miliamps, there is nothing dramatic in terms of current drain. I would have expected to see at least half an amp, not the 2 or 3 miliamps
Something is definitely pulling the battery down, but I can't find what it is. :mad:
Unless the battery is buggered!
 
Sounds like the battery, what size is it? I go for 135AH 1000CCA for the diesel.
You should see 14.2 volts at 2K rpm without switching lots of load on.
Drain is normally 30Ma when the BECM has gone to sleep. Normal drain problem is the BECM being woken up due to the RF receiver picking up srtay signals from WiFi etc.
 
To check whether the RF receiver is the problem, see if yours has a green spot (It's under the offside rear parcel shelf - little black box). If it doesn't it's not the latest version and will probably cause the battery to drain. If it does have a green spot there is a small chance that it's an old version in a new box.. but it's a fair indication it's new.
 
It might not help , but I had a strange battery drain. In the end it was an earthing problem, and it actually wasn't charging properly rather than draining.
 
I've just spoken with a friend who has one of these motors and he says that the earthing cable to the chassis sometimes gets corroded and can stop the car charging correctly, as has been mentioned here by jaygti. Giving it a good scrub up and refix if OK normally does the trick. Also on an american website, the earthing problem was also flagged up as a poor charging problem instead of battery drain.
The battery by the way is a 150ah job so I reckon it is man enough for the job.
I will take a look at the other items mentioned here too, to eliminate them from the issue.
Thanks to all
Dave :)
 
This problem could be caused by a few things. First being the battery isn't a heavy duty brute that these cars require. A slightly worn starter motor, a couple of glow plugs earthing out, dodgy fusebox.
 
try dropping a jump lead from the engine to the battery neg (-) and check the voltage with and with out jumplead . ive have had this in the past on many different cars . secondly see if the batter drains overnight when disconected .
 
autogas said:
try dropping a jump lead from the engine to the battery neg (-) and check the voltage with and with out jumplead . ive have had this in the past on many different cars . secondly see if the batter drains overnight when disconected .
Click to expand...

I will try the jump lead thing to see if that makes a difference. Although the meter shows 14.1 volts over the terminals at 2k rpm.
The battery does hold its charge when disconnected as I left it so for about three days; and when I reconnected it, the engine whizzed over and started almost immediately. I did find one of the glow plugs was leaking as it was blowing bubbles when the engine was running. Swapped it out now, all of them actually, so they should be good.
The leak off pipes are a bit tatty and dribbly though and I will read the existing threads on the problem.
 
It could be the becm itself. They're known for draining the current.

I could probably help you out. We don't charge for testing, you just pay the postage, but at least you'll know if the becm is causing it, & then we could probably fix it for you.
 
Hi all.
I think I have the problem cracked.
My key fob only unlocks the doors and will not lock them. No idea why, so I lock the doors on the key. But, I have been doing the superlock thing, turn the key to lock and then turning again to superlock.
I stopped doing that and hey presto, the engine whizzed over like a mad thing and started almost immediately.
So maybe there is a problem in that area.
I also swapped out the glow plugs as I mentioned previously and sorted the leak off pipes whilst I was at it.
So hopefully, the problem may have gone away; for a while at least.
Doesn't stink of diesel either.
Only thing now is, the system seems to think the bonnet is open all the time even though I know it's shut!!:confused2: Maybe a spray of oil will sort that.
Thanks again everyone.:5bcheers2:
 
Rompingdog said:
Hi all.
I think I have the problem cracked.
My key fob only unlocks the doors and will not lock them. No idea why, so I lock the doors on the key. But, I have been doing the superlock thing, turn the key to lock and then turning again to superlock.
I stopped doing that and hey presto, the engine whizzed over like a mad thing and started almost immediately.
So maybe there is a problem in that area.
I also swapped out the glow plugs as I mentioned previously and sorted the leak off pipes whilst I was at it.
So hopefully, the problem may have gone away; for a while at least.
Doesn't stink of diesel either.
Only thing now is, the system seems to think the bonnet is open all the time even though I know it's shut!!:confused2: Maybe a spray of oil will sort that.
Thanks again everyone.:5bcheers2:
Click to expand...

Bonnet switch is on drivers side bonnet catch. May need adjusting.
 
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