rangerovers.pub
The only place for a coil spring is up Zebedee's arse.
Member
avatar
Joined: Dec 30 2015
Posts: 4124

Going over to France next weekend to investigate a couple of problems with a 99 DSE. Main one is horrendous battery drain, like it can take a fully charged Hankook MF31-1000 down to completely flat overnight. Once the battery is charged it works fine. The only thing I can think that would cause battery drain that serious (without the car bursting into flames) is a short circuit diode in the alternator. As they are 3 phase it will still charge but will drain very rapidly when not charging. Now getting hold of a replacement alternator in France isn't going to be that easy and will probably cost twice what one will cost over here. Buying one here to take over and then finding it isn't the alternator, seems a waste of money too. If anyone has a spare I can borrow for the weekend if it proves that the one on the car is faulty I'll swap them over, bring the old one back and get it reconditioned to return to whoever can lend me one.

Member
Joined: Feb 11 2018
Posts: 261

You're near Peterborough aren't you?

I've got one you're welcome to try. It was working when removed last year as I changed my spare one to a 14.7v set point rectifier and fitted that.

Member
avatar
Joined: Dec 30 2015
Posts: 4124

Yes, Stilton (where the cheese originated from), just off the A1(M). That would be great if I can borrow it, I could come and pick it up if you aren't going to be heading in this direction.

Member
Joined: Nov 16 2016
Posts: 961

I don't want to detract from the main subject of Gilbert getting hands on another alternator... But how easy would it be to detect a broken alternator diode by using a scope to check battery voltage ripple when the alternator is under load?

Member
avatar
Joined: Dec 30 2015
Posts: 4124

If a diode has gone open circuit it should be dead easy. In fact, you can normally see the interior lights pulsing when the engine is idling, because you've only got 2 of the 3 phases doing anything so rather than seeing a smooth DC voltage you'll see a lumpy one. If it has gone short circuit it won't be as obvious because it will still be outputting all 3 phases but a clamp on ammeter will show current being drawn when the engine is off. A check on the main battery feed will show lots of Amps flowing and if you then check on the cable from the alternator and see the same amount of current being drawn that's where it's going.

On a P38 it's fairly easy as each circuit goes via a maxi fuse except for the feed to the alternator and starter. So if you've got a lot of current draw and it isn't going to the starter or alternator, then you just pull a maxi fuse one at a time to isolate where it is going.

Member
Joined: Nov 16 2016
Posts: 961

Gilbertd wrote:

.....because you've only got 2 of the 3 phases doing anything so rather than seeing a smooth DC voltage you'll see a lumpy one.

That's as far as my theory went ;-) but didn't expect ripple to be so obvious you'd notice interior lights flick. I suppose if you turn on stuff that draws enough current you will but pulley gearing will mean the pulsing frequency is a bit on the high side to notice given consistency of vision?

Member
Joined: Feb 11 2018
Posts: 261

Gilbertd wrote:

Yes, Stilton (where the cheese originated from), just off the A1(M). That would be great if I can borrow it, I could come and pick it up if you aren't going to be heading in this direction.

More than welcome. I'm in Boston.
I would drop it off but I don't tend to be that way very often.

Member
avatar
Joined: Dec 30 2015
Posts: 4124

Just sent you a PM

Member
Joined: Jan 16 2016
Posts: 280

I have just had a look in my shed and I have a spare diesel alternator as well.
Unknown condition. Not tested. Bought it a few years ago on Ebay as I remember when it was going cheap and nobody bid on it.
You are welcome to borrow it. I live near Chester.

Member
avatar
Joined: Dec 30 2015
Posts: 4124

Had a run over to Boston on Saturday and picked one up from tanis8472 so all sorted now, thanks. I told the owner of the car (mymysteri) that I suspected the alternator so would be bringing a spare one with me and she reckons her local garage have checked it. I suspect all they did was check that it was charging when the engine was running which it will do even with a short circuit diode. They then suspected the fusebox so reckon they put a spare one on it and the battery still went flat overnight. Knowing how appallingly bad French garages are I don't believe anything they've told her so it will be a start from scratch diagnosis anyway.

In case anyone thinks this is my sole reason for going there, it isn't (not this time anyway). I'm picking Dina up from Charles de Gaulle airport (a very long story as to why she isn't flying into the UK) on Sunday evening so am going over on Saturday to, hopefully, get this job done while I'm in the area.

Member
avatar
Joined: Dec 30 2015
Posts: 4124

and the verdict is, it wasn't the alternator. One of Teri's neighbours has obviously bought themselves a new toy which is sending a burst of data on 433.975 MHz every 2.5 minutes. So after 2 minutes of nothing happening, the BeCM goes to sleep and within 30 seconds at most, it's woken up again. I wouldn't have expected the 0.7A draw to flatten the battery overnight but with a bit more info it seems that the car isn't used every day. So she had been going to it to check the battery, firing it up to make sure it was OK then switching it off again. So it wasn't being run for long enough to put back what had been taken out by starting it. Initially thought about disconnecting the RF receiver aerial, tried to sync the fob which didn't happen. Was then told that the fobs won't sync for some reason so they haven't been used for some time. Door latch is one of Marty's reconditioned ones and the microswitches check out fine. So just unplugged the receiver completely. Current drain is marginal, too low for the clamp on meter to give an accurate figure and it stays that way, so all good. That was Saturday and it was still fine this morning so I'm told.

Just need to get your alternator back to you now Toby.

Member
Joined: Feb 11 2018
Posts: 261

glad to have been able to help.
hopefully she will be ok now.

Member
Joined: Dec 30 2015
Posts: 1109

Sounds like she needs a fob filter... or a 3rd gen receiver!

If there's that much spurious RF then it is possible the keys won't sync, as the signal that actually gets to the BECM, even with the antenna disconnected, could end up garbled by whatever else is being thrown out by the other device.

That or the code the fob is sending isn't match to the BECM (I can't remember if I've had one of her fobs at home with the BECM to check this).

I'd kinda like to see the whole vehicle with everything installed to see if i can work out the fobs etc at some point, but I'm unlikely to have that kind of free time anytime soon!!

Member
avatar
Joined: Dec 30 2015
Posts: 4124

I told her she needed a fob filter, in fact, I very nearly offered to take the one off my car and fit it on hers but then she said she never used them anyway it didn't seem worth it. I did wonder if the lack of sync with the aerial disconnected could be down to the signal having to fight it's way through the car as the Rx aerial is on the RH side but her drivers door is on the LH side. You've already had the BeCM a couple of years ago (still unlocked) and I was able to sync the fobs previously so something has changed. She's got two fobs and originally they both worked, then one stopped and wouldn't sync then the second one went the same way so she doesn't bother any more. The only other weird one with it is that after reconnecting the battery I set all the windows but the drivers window will not set no matter how long you hold the button down but all the others will.

Member
Joined: Aug 19 2019
Posts: 80

About a year ago I tried disconnecting my RF antenna (LHD). I couldn't get the fob to work, even if I held it right near the RF Receiver. I don't have an upgraded receiver, but neither do I have a problem with the battery going flat. I don't know if the NAS frequency is less susceptible to this problem, or if I'm just lucky.

Member
avatar
Joined: Dec 30 2015
Posts: 4124

Depends on what else uses the 315 MHz frequency in the US and Canada. 433 MHz is a Europe wide allocation, and adopted in numerous other countries as well, that is used for 'momentarily operated short range devices' so there's loads of other things using it. If 315 is the US equivalent then the same sort of things will be using it.