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Discussion Starter #1
Yet another RR with the same old electrical problems here. Its a 1998 4.0 SE with a rebuilt Bosch 120 amp alternator. I followed the sticky tests as best I could. Here are the results:

Volts immediately after full 3-stage charge: 12.96
Volts the morning after full charge, battery still disconnected from vehicle: 12.82

1. Engine off, all accessories on for 30 seconds, then off. What voltage:
12.48, then 12.55 a couple minutes later

2. Voltage across battery at idle (no electrical load):
14.13

3. Voltage across battery at 2000rpm (no electrical load):
14.15, remains the same after return to idle

4. Voltage across battery at 2000rpm (everything electrical switched on):
12.35 @ 2000, then after return to idle 11.90

5. Voltage at ALTERNATOR at 2000rpm (everything switched on):
14.37 @ 2000, then after return to idle 13.60
(I left the full electrical load running for the following tests because the instructions didn't specify removing the load)

6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm:
0.455 @ 2000, then after return to idle 0.408

7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load:
1.31 - 1.33 @ 2000 and after return to idle 1.34 - 1.39 -- NOTE these numbers were not stable and varied between the ranges I list here

8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle:
12.58 - 12.61 varied

9. Check voltage drop from 1st ground point to block:
0.374 - 0.379 varied

10. Check voltage drop from Alternator Housing to block:
-0.002 -- is this even possible? I then tried to measure from Alt housing to the engine hoist ring since the ring is the recommended negative for jumpstarting, and I got 0.000 -- I've noticed that it isn't possible to jumpstart using the hoist ring for the negative lead.

11. Voltage from alternator positive to alternator housing:
14.24, and 1 minute later 12.59

As an extra test I tried the battery again at idle and got 12.33 - 12.36

After shutting down and waiting a couple minutes the battery measured 12.48.

The full load included:

  • High beams[/*:m:2bjmc6u0]
  • both seat warmers[/*:m:2bjmc6u0]
  • Both window defoggers[/*:m:2bjmc6u0]
  • AC[/*:m:2bjmc6u0]
  • Hazards[/*:m:2bjmc6u0]
  • Fog lights[/*:m:2bjmc6u0]
  • Doors open[/*:m:2bjmc6u0]
The alternator is a rebuilt Bosch 120 amp from Auto Parts Warehouse and is only 3 months old. The battery is a Kirkland 900 CCA from Costco (I know its a bit small, but its was the largest CCA they had, and I love Costco's policy of taking anything back no questions asked. Since 900 is still over the dealer's recommendation I thought it might be okay).

Before I bring it in for service I wanted to hear any of the forum's opinions -- I've noticed that I usually get better results from mechanics when I can say "This is what needs to be fixed" as opposed to "Here are some weird symptoms, please fix and please be kind to my wallet".
 

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2002-2005 Range Rover MkIII / L322
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I'd like to congratulate you on one of the best first posts ever.

Unfortunately though, I can't give you any insight that's definitely correct, so I'll bite my tongue for now.
 

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I ahve to concur with Mag. You have to be the best new member ever. Shoot me your adress and I will make a donation in your name and send you RRnet stickers for just how complete a first post you have made.
 

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1995-2002 Range Rover P38A
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rrtoadhall said:
I ahve to concur with Mag. You have to be the best new member ever. Shoot me your adress and I will make a donation in your name and send you RRnet stickers for just how complete a first post you have made.
Agree with the both of you, great first post!

So what are your symptoms anyways? We could me moving in the wrong direction with this.

Welcome again!

rrtoadhall - Happy Birthday BTW!

Edit - mag beat me to the question...
 

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Discussion Starter #6
I posted everything but the symptoms -- well here they are in no particular order:

  • Gearbox Fault message always on[/*:m:w3signts]
  • Battery keeps dying, requiring jumpstart[/*:m:w3signts]
  • Even after jumpstart and over an hour of driving, if I turn it off, it won't turn over[/*:m:w3signts]
  • Intermittent acceleration hesitation, especially going up hill[/*:m:w3signts]
I did pull the plug on the RF receiver -- not just the antenna plug but the whole thing -- to see if that was the cause of the battery. My remote is broken so I only use the key anyway. but the battery was dead again the next day. So I figured it was time to go through the electrical check list.

There there is often a clunk from what could be either gearbox or front tranfercase under deceleration from 3rd to 2nd gear and again from 2nd to 1st -- of course this could be genuinely mechanical, but I'd like to solve the electrical problems just in case they are related.
 

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I am assuming yours is a GEMs model. I have been having this STUPID temp sensor problem for a year now and have yet to find the cause of it. I decided to insert some fuses that seemed to be missing in the fuse box... Maybe it would fix the problem. NOT! It actually caused the battery to loose its charge even when the vehicle was running!!!!! I have no idea what the fuses were for, but figured they were removed for the battery drain. Thank GOD i brought my battery charger and jumper cables with me last weekend (it was a Land Rover event too. Had a great time and have been meaning to post pics ;) ). Maybe someone can shed some light on this, they were fuses F28 and F35. It could be completely unrelated to your problem, but its my 2 cents worth.
 

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Discussion Starter #8
Yeah, my BECM was draining over 4amps. Culprits were on fuse 9, 1 and 15 found in fusebox under passenger seat. Hungry gremlins.
 

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Does the BECM go to sleep on yours? It should after 2 minutes or so. The easiest way to tell is to look at the "P" light on the transmission. There will be a faint light that stays on when the BECM is active.
 

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I just had similar symptoms.

The problems were solved by cleaning up the corrosion from the earth leads.
 

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I back the others there. I'd go straight to the earths & clean them all up.

Take the no nonsense approach. Unbolt the body connections & resurface the contact area with a grinder.
 

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2002-2005 Range Rover MkIII / L322
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7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load:
1.31 - 1.33 @ 2000 and after return to idle 1.34 - 1.39 -- NOTE these numbers were not stable and varied between the ranges I list here
This is the one that caught my eye at the beginning... but I wasn't 100% sure. That seems a bit excessive and could be indicative of the ground issue. Hopefully (fingers crossed) that's what it is.
 

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Discussion Starter #14
kmagnuss,
A ground problem seems likely -- I mean, why else would I not be able to jumpstart the vehicle using the engine hoist ring for the negative lead like the manual suggests?

That said, where can I find a list of all the grounds I need to check?

lrscott,
Yes my BECM now goes to sleep -- after I pulled to power from the RF receiver. My remote is broken, so the receive wasn't doing me any good anyway.

BTW, thanks so much to everyone for trying to help out here.
 

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Hi Niblettes, great detail thanks.

Along with details of the tests, the sticky gives specifications on acceptable values. They are honest specifications and you need to get back within them.

Your positive voltage drop is approximately 1330mv. You are allowed 120mv

Your negative voltage drop is 455mv you are allowed 120mv.

Your total voltage drop is nearly 2 full volts! It is almost 10 times the MAXIMUM acceptable value.

Your battery still seems to be OK just - you haven't yet totally killed it by flattening it but you nearly have. It is 20mv outside of specification but I wouldn't worry about that yet. But expect to have to replace it again sooner as it has been damaged and its life shortened.

Now what you really want is information on how to fix it...

You have problems with the wiring between your alternator and your battery. Both wires have major problems. Cleaning every spot (terminal) between the alternator posts and battery posts inclusive will help. Scratch them with a file to get all rust and crud off them you want a nice electrical connection.

Then just run two additional cables. One nice big heavy red one from your alternator terminal to your battery positive and the other from the alternator body to the battery negative.

I've used 2 gauge cables which are quite sufficient but no harm in using bigger.

Anybody got a photo of a nice wire run to help Niblettes out? Mine aren't all that neat as I have a lot of accessories but I can possibly take a photo tonight.

Greg
 

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lrscott said:
I have been having this STUPID temp sensor problem for a year now and have yet to find the cause of it.
Which stupid temperature sensor? What is the exact fault? The precise words on the screen or the full detail of the symptoms.

If it says "Gearbox overheat" that can be caused by pressure washing the car and buggering the gearbox temperature sensor on the radiator. It is actually on the gearbox oil cooler mounted to the radiator and from memory, the sensor measures the oil temperature after it leaves the cooler.

With a P38 I promise you, any problem you have has already been covered on this site, it is just a matter of knowing what to search for.

Greg
 

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Discussion Starter #17
Update:

After asking for a wire gauge under 4 at a large nationally branded auto parts store (Crappy Tire) I was told by the guy behind the parts desk to go to the wire section in the hardware department. Just like I suspected they didn't have anything near that gauge. So I tried calling around. Got mostly similar unhelpful answers.

Then I got the brilliant idea of asking specifically for batter post cable. Ta da! I found a whole wall filled with different lengths and gauges of battery post and starter cable. I grabbed a couple 4-gauge started cables -- that was the biggest they had.

At home I pulled off all the grounds, cleaned them up, and then added an extra cable alternator housing to negative battery post and another from the alternator positive to the battery positive post.

I fired it up and here are the results:

1. Engine off, all accessories on for 30 seconds, then off. What voltage:
THEN----------NOW----------DELTA
12.48----------12.63---------- +0.15


2. Voltage across battery at idle (no electrical load):
THEN----------NOW----------DELTA
14.13----------14.32---------- +0.19


3. Voltage across battery at 2000rpm (no electrical load):
THEN----------NOW----------DELTA
14.15----------14.34---------- +0.19


4. Voltage across battery at 2000rpm (everything electrical switched on):
THEN----------NOW----------DELTA
12.35----------12.32---------- -0.03


5. Voltage at ALTERNATOR at 2000rpm (everything switched on):
THEN----------NOW----------DELTA
14.37----------12.44---------- -1.93

(I left the full electrical load running for the following tests because the instructions didn't specify removing the load)

6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm:
THEN----------NOW----------DELTA
0.455----------.075---------- -0.38


7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load:
THEN----------NOW----------DELTA
1.320----------0.134---------- -1.186


8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle:
THEN----------NOW----------DELTA
12.60----------0.110---------- -12.49
(I'm not sure I measured properly here, this delta seems odd)

9. Check voltage drop from 1st ground point to block:
THEN----------NOW----------DELTA
0.376----------.063---------- -0.313


10. Check voltage drop from Alternator Housing to block:
THEN----------NOW----------DELTA
-0.002---------0.002---------- same


11. Voltage from alternator positive to alternator housing:
THEN----------NOW----------DELTA
14.24----------12.35---------- -1.89


Voltage after shutting down and waiting a minute:
THEN----------NOW----------DELTA
12.59----------12.88---------- +.29


Not only did this improve my test results, but it also seemed to fix a couple other nagging problems (at least for the duration of my first short test drives):

1. "Gearbox Fault" stopped showing up on the message centre. It did make a return after I pulled into the driveway, parked and turned off the ignition. I'll look into this shortly. But at least the persistent message is gone.

2. The vehicle always had an annoying heavy "clunk" when gearing down from 3rd to 2nd, and from 2nd to 1st. Well, that seems to have been fixed. This makes some sense too. Perhaps the transmission wasn't getting enough juice to do its job properly, and now it is -- which could also explain the "Gearbox Fault" thing too.

3. The RR used to stutter sometimes through acceleration. Usually this happened at speed, up hill. I didn't get a chance to that for the first test drive -- but I'll test that soon.

Thanks so much for this test checklist and everyone's help.

Now on to my next RR project -- Improving its fuel economy.
 

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Niblettes thanks for coming back with your reply.

Your numbers are grealy improved. I think you took my "everything electrical switched on" a little too literally. At 2000rpm, your alternator should be able to make enough juice to run everything but it isn't in your car. All your wiring is now in order but the alternator is a little weak for the full load. From your earlier post however you have more electrical stuff switched on when you do the test than I do so maybe we are justing asking too much of your alternator. I don't have heated seats for example so I've never had that load on during a test.

Rerun the 2000rpm everything switched on test except this time only turn on your high beams, rear window demister and full blower fans. Tell me what voltage you get across your battery then (at 2000rpm). From when you turn all this gear on, quickly get around to the battery and get the 2000rpm on. Your alternator will lose the battle against all this gear unless you are doing some RPM. eg 1500+. If you take a while to get the RPM on, then your battery will be draining and then when you do get the RPM on the alternator has to supply all the accessories AND charge the battery.

To assist this check, hold the car at 2000rpm for 20 seconds before you take the measurement to allow the battery to recover a little and the alternator to lift right up. Continue to hold 2000rpm and keep testing until it settles (no more than 2 minutes though). I'd do this in neutral, not park.

"I think" your problem is actually totally fixed and you had too many electrical things on for the test. Alternatively, your alternator is weak and we might as well find out now.

Your gearbox fault message would have been caused by your electrical problems.

I can make mine have a gearbox fault at will. If I start the car and very quickly move from park to drive, I get the message every time. I mean FAST, probably about the same time as I take my hand off the key. Mine is a 94 build car so possibly the later ones have better software and don't do this - but I would not be at all surprised if they still did.

Once I do this, the transmission slips a lot more eg 2000rpm to start moving instead of say 800rpm. It clunks between gears as you described. I can't give you great detail as it seems that it would be very bad for the gearbox to drive like this, so I don't. I simply stop the car, put it into park, switch it off, restart it and then put it into drive slightly more slowly. I've done this accidentally maybe once every 2 years since I owned the car.

Re your fuel economy, check your crankcase breather hose (make sure it doesn't collapse and that it seals properly), your MAF is clean, your O2 sensors are reporting what they should (another job for a multimeter!).

Your 4 gauge cable would be the minimum I'd use, it seems OK. Just. Can you please post a photo?

Thanks again for the detailed update. Many people dont' take the time to reply once their problem if fixed. These posts are good for people to search in the future.

Greg
 

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Glad to see things worked out for you. I should do what you did to mine and see if that helps some if its little nagging problems. Interesting that your transmission's clunk went away after this too :think: .

Which stupid temperature sensor? What is the exact fault? The precise words on the screen or the full detail of the symptoms.
Its the coolant temp sensor on the instrument cluster. If there is too much resistance in the system, usually a bad ground can cause this, the readings will be erratic. There is a "fix" for it on roverparts.com. However, most of the time fixing the grounds will fix the problem. Mine still reads erratically, but I've learned to live with it `) .
 

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lrscott said:
Glad to see things worked out for you. I should do what you did to mine and see if that helps some if its little nagging problems. Interesting that your transmission's clunk went away after this too :think: .
If you are getting a gearbox fault message then this could be the same problem in your car. i doubt it if you are not getting the message. However, if you haven't run the tests, you should. All p38 owners should fix their electrical system before they end up wrecking expensive good batteries etc and still having to fix it anyway.

Also, I think you mean coolant temperature gauge, not sensor?
 
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