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This one is doing my head in! Mk1 sons td5 disco, ,53 plate Battery wouldn’t start it, so he bought another Two days later i checked the old one, been sat outside, still showing over 12v so I refitted it, 3 days later it’s so flat not even the interior light works Charged it up, it holds charge Refitted, put an ammeter between neggy terminal and cable, not showing anything ( cheap multimeter- bear that in mind) Put voltmeter between same - volts drop 0.01 every 20 seconds or so Connect a bulb between terminal and lead, it lights, not brightly, but pulses about every second then after about a minute it goes out, then relights Start pulling fuses, battery fuse removed (10A in engine bay) light goes out Online search says this fuse supplies body control unit, instrument pack, IDM?? And inertia cutout Disconnect inertia switch, no change What the heck is going on? Never had a pulsing test lamp before, I’d rather have a rod through the block than an elec fault!
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Does the new battery start it OK and not go flat? You can't check a car battery properly with a multimeter, you need a load drop tester.
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lrman
Part of things
Posts: 41
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Sounds like you know what circuit it’s on, I would unplug the instrument cluster next as likely to only be one or two plugs. If it’s not that then your looking at a BCM, unplug that next but it will have a few more plugs on it and if memory is right it’s on the left behind the dash. When I worked at Land Rover years ago it wasn’t in heard of to replace a BCM. Only other tip I’ve got is check any body earth points that the instrument cluster or BCM use as I’ve had them loose and that’s caused issues as well. Cheapest solution may be a earth cut switch on the battery but depending what use the disco gets this might not be viable.
Edited to say. Use the amp draw function of your multi meter if it’s got one. Most only handle 10 amps so be careful what you switch on with it connected. It’s should have less than 0.02 once locked after max half an hour. You will see the amps drop as different ECU switch off.
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Last Edit: Apr 2, 2020 18:31:51 GMT by lrman
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scimjim
Club Retro Rides Member
Posts: 1,503
Club RR Member Number: 8
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I had a similar drain problem on a p38, that was the RF receiver (alarm/key) keeping the BCM in “awake mode” instead of going to standby. Known problem and an upgraded module was available off the shelf?
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Last Edit: Apr 2, 2020 18:35:43 GMT by scimjim
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Thanks all, I do have another scrap disco sitting here, so I might start swapping bits over, after the weekend since I need the car for a house move on Sunday Currently I’m just keeping the battery disconnected until I need to start it, it starts fine on either battery, or did. I’ve not had chance to see if the new battery goes flat too because it’s now 10 miles away in a series landy that’s providing him with transportation since he doesn’t live here If I fit another bcu does it need programming to the car? The scrap disco also has a working rf unit, since I tested it before I stripped it
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Sounds like same issue that affects the P38 - stray RFID transmissions stops the BECM going into sleep mode.
Latest RF receiver fixes it although now NLA - someone (p38partsshop?) has engineered a module that pre-filters the RF between it and the BECM to stop it waking up.
Swapping units between cars is a minefield - the BECM, engine ECU and key are all linked. Swap one and nothing works..
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Last Edit: Apr 2, 2020 20:21:54 GMT by Phil H
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Thanks Phil, I suspected that was the case, is the p38 unit the same between the p38 and disco 2 then? It so happens that I’ve got a scrap one of those sitting here as well, this place is like a Land Rover graveyard! 🙄
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Phil H
Posted a lot
Posts: 1,448
Club RR Member Number: 133
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Just had a quick google and it’s a different unit on the D2 to the P38 (although it seems the same can possibly affect it - stray RF).
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Just had a quick google and it’s a different unit on the D2 to the P38 (although it seems the same can possibly affect it - stray RF). Thanks for that, the d2 is more stripped than the p38 anyway 😀
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