P38A Battery Drain

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Graham.GRS

New Member
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5
Location
Midlands
Hi Guys, happy new year! I have the dreaded P38 battery drain, story so far. New battery fitted as owning the car 3 years thought battery had past its sell buy date. New driver door mechanism fitted as wouldn't accept EKA code when battery went completely flat. Watching the red light next to auto gear shift it goes from fully illuminated when driving to a faint glow when car locked but doesn't go out after a few minutes. Have removed antenna wire to RF receiver made no difference and have checked I do have latest unit with two PCB's inside. A local LR guy had for three weeks and disconnected various items around car but still no joy. He hadn't got Nanocom device to interrogate BECM fully. I'm wondering whether I have a faulty BECM? I have checked with Hawkeye device and all body functions check out ok but I do have a very intermittent issue with the right blend motor but drain issue is constant. Can any body offer any advice on how to resolve this issue? A guy suggested pulling fuses until the current drain stopped but I know the BECM is not sleeping so 1A drain will be present. I'm not sure how to fully test the data inputs to the BECM, I understand that any incorrect data from these inputs will prevent the unit going to sleep. I do enjoy driving this vehicle it always puts a smile on my face heating that V8 burble but I am coming close to getting rid as need a reliable vehicle I can come back to after working away for 3/4 days. Any help or advise would be greatly appreciated.
Regards
Graham
 
If you have the very latest RF receiver then that isn't your problem.
Have you proved conclusively with an ammeter that the car is "waking up"?
There are other things that can wake the BeCM up I believe. Failing doorlock switches for instance.
Do your locks ever "cycle" as you drive along?
Is there an after-market radio or sat-nav fitted?
 
Gear shift indicator stays at a faint glow so BECM not sleeping. Driver door mechanism replaced others function correctly no message on dash re door open etc.
 
There was a small weather station i had that was the same frequency as the RF and that was draining my battery..

Once disconnected the Car would start after being stood for over 3 weeks.

Perhaps you have interference in your particular area.
 
DanClarke said:
If you have the very latest RF receiver then that isn't your problem.
Have you proved conclusively with an ammeter that the car is "waking up"?
There are other things that can wake the BeCM up I believe. Failing doorlock switches for instance.
Do your locks ever "cycle" as you drive along?
Is there an after-market radio or sat-nav fitted?
Click to expand...
Even the latest receiver can fail. Unplug the receiver and see if the drain stops.
I believe the ultrasound sensors for the alarm can also keep the BECM awake.
OP jumping to the conclusion that the BECM is faulty is not a good idea.
 
If you can fool the bonnet-switch with a screwdriver or similar to think the bonnet is shut, and put a sensitive ring-clamp ammeter on the battery lead you can see the current draw from initial locking and then after the BeCM goes to sleep it should drop to 30milliamps or thereabouts. The attached guide gives a process to follow. It uses an "in-line" ammeter for the measurements, but now that ring-ammeters of sufficient sensitivity are available quite cheaply, they are a lot less fuss to use.

Also, here is a u-tube of a guy testing his.

Good luck!
 

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What Datatek said is good advice.
I had the dreaded battery drain syndrome a few tears ago and understand how annoying it is. Flat battery every morning and even after starting using a battery pack, without the full amps in the battery it throws up all sorts of issues. At that time driving 70 mile each way for work, battery was charged and then overnight flat. It was so frustrating and annoying. Luckily for me just removing the RF lead stopped all my issues. Which I am pleased about as I still get a great joy from driving my P38 even though its only for a few months a year and always a Russian winter so a good Battery is crucial here. Its worth persevering to try and find the gremlin. I drive a different vehicle for the rest of the year throughout Europe and always look forward to getting back to the Rangie.
Good luck Graham and hope somebody better qualified than me on here can help.
 
Or failing that, check the alternator is kicking out at least 13.8V. If you have a full calcium battery you'll need to upgrade the set-point to 14.5V or it'll keep killing batteries. Also check the alternator isn't leaking current - i.e. diode failed.
 
I have heard that the wipers for the headlights not being "parked" correctly can drain your battery as well, I don't know if that's true or not, but it will just take a few second to see and then can be discounted.
 
Another one, but I have no experience of it and it might just be "legend" is that the BBUS sounders backup battery cannot hold charge and keeps leaching power from the main battery.
I have a vague recollection of coming across a list of all things that could "wake" the BeCM from slumber, I shall go look for it.
 
DanClarke said:
Another one, but I have no experience of it and it might just be "legend" is that the BBUS sounders backup battery cannot hold charge and keeps leaching power from the main battery.
I have a vague recollection of coming across a list of all things that could "wake" the BeCM from slumber, I shall go look for it.
Click to expand...
The BBUS sounder battery charge current will be very low, so I doubt a duff battery will increase the drain by much but certainly worth checking. The sounder is unplugged on both mine.
 
What battery are you using? I managed to cure my battery drain using a dying battery by unplugging the RF box altogether and knocking off interior lights (hold middle button down). I could then manage on a dying old unit, so decided to upgrade per Datateks advice to 120ah 1000cca battery after doing what I could to stop it draining. No trouble since :)
 
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