1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.
  2. Welcome To LandyZone!

    LandyZone is the biggest Land Rover forum on the net. We have plenty of very knowledgable members so if you have any questions about your Land Rover or just want to connect with other Landy owners, you're in the right place.

    Registering is free and easy just click here, we hope to see you on the forums soon!

P38A Electrickery drain,where am I going wrong?

Discussion in 'Range Rover' started by tomcat59alan, Mar 6, 2018.

< Previous Thread | Next Thread >
  1. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    Hi,peeps, I have a drain on the battery:eek: drop tested the battery and its fine. Disconnected the battery then reconnected it with a test lamp between the earth lead and the -'ve post. Lamp lit and stayed illuminated while I pulled every fuse and relay. I even disconnected the + wire to the towing socket. I have also disconnected the +from the alternator to eliminate a diode failure .Help,please
     
  2. DanClarke

    DanClarke Well-Known Member

    Joined:
    Mar 13, 2009
    Posts:
    1,693
    Likes Received:
    1,287
    Location:
    Benfleet, Essex
    Errr...isn't the BeCM and the RF receiver also "Always on" and drawing a tiny current even in the best of times?
    Or, Is there a failed diode in the Alternator pack allowing some weird draw?

    I will watch this thread because I have a constant draw on the battery too and mine leads to a flat battery in a matter of days and mine is a 110AH battery so that's some draw.
     
  3. Kev12

    Kev12 Active Member

    Joined:
    Jan 1, 2018
    Posts:
    275
    Likes Received:
    91
    Location:
    Cornwall
    I think you need to fool it that the bonnet is shut then lock it and wait for the becm to go to sleep to test for drains on these?
     
  4. Saint.V8

    Saint.V8 Dyed-in-the-wool 100% RR Junkie

    Joined:
    Apr 27, 2008
    Posts:
    15,122
    Likes Received:
    1,305
    Location:
    Surrey - Near the middle, close to some green bits
    Test lamp would do little - except light up...and it would indeed light up regardless of power drain, as it is 'in the circuit' of everything that both switches off and remains on (RF unit, EAS timer etc etc)....

    Only true test would be to measure current draw with an meter.....a light simple shows a flow of electrons - not how much uummpphh they have.
     
    Al2O3 and K14 like this.
  5. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    I put a spare bonnet catch in the o/s lock to fool it.;)
     
    Last edited: Mar 7, 2018
  6. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    Cheers Ant, I'm trying to think of everything that stays live and draws power with the ignition off.. my r/f cannot be activated by spurious signals due to @brianp38dse 's second fob work around. All I can think of is the clock and the becm. We could do with a dummies "how to guide for drain detection" any takers? @martyuk ?
     
  7. brianp38dse

    brianp38dse Well-Known Member

    Joined:
    May 13, 2014
    Posts:
    4,342
    Likes Received:
    1,403
    Location:
    heathrow
  8. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    Morning Brian, I hate electrics!!! Probably because I don't understand it. I had a test lamp between the disconnected earth lead and the - battery post and it illuminated which, correct me if I'm wrong means there is something drawing power from the battery. I pulled every fuse and relay one by one to try and isolate which circuit is drawing power. The light didn't go out which I guess means the drain on a circuit that is constantly powered. Instead of the lamp I need to connect a multi meter but set to what? :confused:
     
  9. Wazzajnr

    Wazzajnr Well-Known Member

    Joined:
    Apr 25, 2016
    Posts:
    1,304
    Likes Received:
    348
    Location:
    Chorley
    Not strictly true, if the current drawn by the other circuits is only a few mA then a large wattage test lamp might not illuminate.
    That said you are entirely correct that the only way is with a multimeter set to amps. Only problem then is that if something takes a large chunk of current, you could pop the meter.
     
  10. brianp38dse

    brianp38dse Well-Known Member

    Joined:
    May 13, 2014
    Posts:
    4,342
    Likes Received:
    1,403
    Location:
    heathrow
    Set meter to amps and conect it between the negative post and the earth lead and it will tell you the current draw, you are looking to have a reading of point somthing millamps.
     
    tomcat59alan likes this.
  11. Pete The Biker

    Pete The Biker Active Member

    Joined:
    Apr 25, 2010
    Posts:
    506
    Likes Received:
    28
    Location:
    Leicestershire
    I think for most cars the standby current is in the order of 25 to 50 milliamps (0.025 - 0.050 Amps)?

    I might be imagining it but I think you can sometimes get a short through the alternator - might be worth trying disconnecting that?

    Pete
     
  12. Fergie46

    Fergie46 Active Member

    Joined:
    May 7, 2014
    Posts:
    350
    Likes Received:
    82
    Location:
    Dorset
    Tiresome isn't the word - sometimes mine will be ok for a couple of weeks or more - others it will flatten my battery in two days. RF disconnected.

    No rhyme or reason to it, the BeCM must suffer from periodic insomnia trawling the circuits and looking for a playmate.
     
  13. Saint.V8

    Saint.V8 Dyed-in-the-wool 100% RR Junkie

    Joined:
    Apr 27, 2008
    Posts:
    15,122
    Likes Received:
    1,305
    Location:
    Surrey - Near the middle, close to some green bits
    I am not disputing as I am not an electrician or electrical whiz....but lets say the lamp is put into the circuit at the battery as per Alan's thinking.

    There is a leak, and this leak (without the lamp in the circuit) would draw 0.5 amps....because that is what the components contributing to the leak are drawing from the battery....add an additional load to that leak - the test lamp - the current draw will go up through the leak circuit as you have now added an additional load to the circuit (the lamp) so the leak is now drawing 0.5A and (lets say) 1A for the test lamp, the current draw is now 1.5A...the lamp will still illuminate, unless the voltage being returned through the leak due to resistance is less than that to 'excite' the test lamp.

    As you say, only true test is to check with a meter.
     
    Al2O3 likes this.
  14. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    Cheers,see end of post#1.:)
     
  15. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    The only way I could get excited by electrickery is to plug myself into the mains:eek::D
     
    Kev12 likes this.
  16. Pete The Biker

    Pete The Biker Active Member

    Joined:
    Apr 25, 2010
    Posts:
    506
    Likes Received:
    28
    Location:
    Leicestershire
    Bugger! There was me thinking I had a good idea!

    Good luck with your search.

    Pete
     
    tomcat59alan likes this.
  17. Wazzajnr

    Wazzajnr Well-Known Member

    Joined:
    Apr 25, 2016
    Posts:
    1,304
    Likes Received:
    348
    Location:
    Chorley
    It doesn't work like that.
    If, as you say there is 0.5A being drawn by other things on the car and you add in a 5w lamp then yes, it will illuminate. However the total current being drawn from the battery will be very slightly less because the lamp is a higher resistance than the earth cable.
    All that will happen is that the lamp will become one half of a potential divider.(with the rest of the cars circuits being the other half)
    However if you tried the same experiment with a 55w lamp on a car drawing 0.5A it probably wouldn't illuminate at all. (it might glow slightly)
    The total current flowing in the circuit will go less as you add more lamps because the resistance will go up.
    I'm not in any way trying to belittle anyone, just trying to explain that a lamp in the circuit really doesn't work for the reasons above.
     
    Al2O3 and Saint.V8 like this.
  18. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    Well that helped me, and I know feck all about the dark art.;) waiting for some patch leads for the multi meter then I'll have another go. So regretting not buying the Vogue :(
     
  19. DanClarke

    DanClarke Well-Known Member

    Joined:
    Mar 13, 2009
    Posts:
    1,693
    Likes Received:
    1,287
    Location:
    Benfleet, Essex
    Don't regret anything @tomcat59alan mine's a Vogue and its equally crap on the electrickery front.
     
    tomcat59alan likes this.
  20. tomcat59alan

    tomcat59alan Well-Known Member

    Joined:
    Apr 3, 2011
    Posts:
    9,967
    Likes Received:
    1,685
    Location:
    wirral and triquivijate
    If it's any consolation mine was perfect today ,perhaps they are in contact with each other and amusing themselves .
     
< Previous Thread | Next Thread >