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Discussion Starter #1
Hello everyone,

Newbie here, and sorry if this question has been dealt with before, but a search didn't find what I was looking for.

My 14 year old P38 4.6 petrol has been starting ok, even when using it infrequently. Used it for work yesterday and to drive home, calling in for petrol on the way. This morning the doors wouldn't unlock with the key pad. There was no electrical power at all, and I tested the battery with my meter, and it registered 3.6 volts!! The lights had not been left on, and everything was left as normal.

Cutting a long story short, I eventually got my Ford tractor and tried to jump start the P38. With the jump leads connected, there seemed to be good power, and all the dash lights came on as usual. Now this tractor has a very large battery, but even when the message 'Start Engine' appeared, the engine would not turn over, just a very short 'whrrr' , and nothing, no panel lights etc.

I'm completely baffled because I've had flat batteries before, and just re-charged them and the engine fires up OK. I've even jumped started it when my wife left the lights on in the supermarket, but this time - nothing!

My first thought is that perhaps the alternator has gone and is shorting out the battery, but there was no sign of trouble when I got home last night. Obviously there is a power leakage somewhere, but where? Your suggestions as to a possible cause will be most welcome! thanks.

Geoff
 

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Hi, and welcome.

I would suggest following and filling out the electrical stickey at the top of the forum. That is a good place to start troubleshooting your problem.
Check all your connections are tight too.
On a side note; I just had a sort of similar problem as yourself. I couldnt figure it out, and just kept putting my battery on a charger each night when I parked it. I replaced a couple of optimas to try to remedy it, but to no avail. I finally figured it out when my starter completely died. When I went to change it, I found the positive lead from the battery was severely deteriorated and fried (burnt looking) at the connector that goes to the post on the starter. I changed out the starter and replaced the cables, and no more battery drain problems. Plus, now the car starts faster and better than it ever has.
 

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With a battery voltage as low as 3.5 V there is something definately wrong.Trying to jump start is not a good idea.It is possible your battery is beyond use and may have a shorted cell.Yes it can just happen overnight.I suggest you try to recharge your battery after disconnecting it from the RR and see if it is recoverable as a first step. :pray:
 

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Discussion Starter #4
Thanks for your speedy replies.

I have already disconnected the battery, and it is on charge. It may not recover as it has drained so low, but we'll see. I have another battery that's been on charge all day, and I'll try that one in the morning.

Thanks again.

Geoff
 

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John W said:
With a battery voltage as low as 3.5 V there is something definately wrong.Trying to jump start is not a good idea.It is possible your battery is beyond use and may have a shorted cell.Yes it can just happen overnight.I suggest you try to recharge your battery after disconnecting it from the RR and see if it is recoverable as a first step. :pray:
Good point John. That low of voltage overnight could be a really good indication of a faulty battery. I usually take alot longer than most to find the solutuion because I often tend to overlook the obvious steps first. :lol:
 

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Discussion Starter #6
Hi Gents,

I trickle charged the battery overnight, and after re-setting the door/key code, the engine fired up. alternator obviously doing its work, and I've now switched off. Battery voltage was 12.68. I'll disconnect it shortly, and see what happens. My guess is that, as you suggest, the battery's u/s. It'll be interesting to see what the voltage is before I disconnect it.

Geoff
 

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Discussion Starter #7
Hi Guys,

The battery voltage dropped to 12.4 in the evening, and was still 12.4 in the morning. I took battery to my workplace Monday, and it tested OK. Re-connected, started engine OK. Switched off and checked the voltage, 12.6 Two hours later is was down to 9.6 volts. :(

One thing that I can't re-set is that when I remove the ignition key the warning message shows 'Key in Ignition', which it clearly is not!

I'm having a diagnostic test done in the morning (Wed), so hopefully I will know more then.

Geoff
 

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GWRfan said:
One thing that I can't re-set is that when I remove the ignition key the warning message shows 'Key in Ignition', which it clearly is not!
Squirt some Graphite Powder in to the Ignition Barrel/Key I'm pretty sure that will cure that problem. Do Not use WD40 or the likes of.

Cheers
 

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HI had the same problem with mine key in the ignition message squited with graphite grease and has cured the problem :dance:
 

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Discussion Starter #11
Thanks Nelly.

Took the P38 for a diagnostic test today. Battery and alternator seem to be ok. The test was rather inconclusive. One 'error' message was that there was 'no voltage to pin No1 on ECU' . No idea what that's all about, but I've left the key in the ignition at present and will check voltage loss after an hour or so. There has to be a reason for the voltage loss, but everyone's guessing, LOL.

Geoff
 

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Geoff,
Have you checked whether your BECM is going "to sleep" correctly.
There is a RED light next to the gear selector.This light should extinguish completely after a delay when have you locked the vehicle.Best to observe in low ambient light conditions.If it does not then the BECM is drawing too high a current and will drain the battery overnight. :think:

I am not certain,but "the key in ignition message" may be keeping the BECM awake.
 

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Discussion Starter #14
Just removed ignition key after an hour, with battery showing minimal loss.

One other thing, the key fob will not automatically lock the doors, although it does unlock them. I have to use the key to lock them. Seems there are some strange forces going on in the electronics! and unfortunately, I no nothing about them.

Thanks to all for your help so far.

Geoff
 

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HI ref key won,t lock door are you still getting key in ignition message on dash i think you will find this is the problem safety feature i think to stop you locking keys in car although you would have to have a spare fob to do so when you take the key out just give it a wiggle on the way out to make sure the barrel comes out properly if it does you wont get message on dash and should be able to lock it on the fob hope this helps neil `)
 

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Discussion Starter #16
Hi Nelly,

I sat in the RR and reset all the windows, and found that the key in ignition message no longer showed. I don't think this was anything to do with the battery discharge, but thought the electrics might somehow still be thinking that something was switched on!

Anyway, I'm sure there is nothing left on, and the battery went down to 5.6 volts since 11.30 this morning (5 hours). Strangely though, when I disconnected it, the reading went up to 9 volts!

I've booked it in for another test for next week. My nearest RR dealer couldn't look at it for 2 weeks!

Geoff
 

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Discussion Starter #17
Hi All,

Just an update.

The RR went to the garage last Wednesday, and nothing was really found. the mechanic fiddled around with the larger fuses (next to the battery), and thinks one of them was possibly causing the problem (the one nearest to the battery I believe). anyway, after 2 days in his yard the vehicle started OK, and has been home since Saturday. The voltage was about 12.4, and today (Wed) it was 12.2, and the RR started first turn of the key.

So I don't really know what caused it to run down like it did. :?

I'm now thinking of buying one of those small solar panels, so I can trickle charge it throughout the week. What do you think? `8)

Geoff
 

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I had the same idea with the solar panel but from what I've read the output is way too small to charge the battery and power insomnia suffering BeCMs. I have read here about stray radio signals waking the becm so I disconnected the alarm receiver aerial and it looks like my draining problems are gone, although the jury's still out on this.

Can't find the link on rr.net right now but you'll find the receiver under the trim on the right side of the boot. If I remember correctly it's a blue connector.
 

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I too suffered this problem until I found the vehicle tracking unit and promtly ripped it out, problem solved.
The battery on the tracker unit had gone bad and the charge circuit was trying to charge it up all the time..it was very warm and could have been a potential fire hazard
 

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I'm a newbie here, bought a 1996 4.6 HSE with LPG conversion about 4 months ago. Had a similar problem as you when I parked outside my house. Battery was flat every morning and the door remote lock failed on the drivers side. Took it to the dealers and they could find no problem. First night home battery flat again. Turned out it was my wireless internet activating the BECM via the key fob RF unit under the rear RHS shelf. Apparently this is qiuite a common fault so I replaced the RF unit with the later one and the problem was solved.(not cheap at about £160 but don't be tempted to buy on ebay as I've seen one or two of the old units on there with the tag "found it in back or car when I purchased it")
 
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