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Discussion Starter #21
Alrightly folks the results are in from the testing. All numbers were identical at idle and at 2000ish rpm.

Under load(lights only HVAC doesn't work due to this issue) fresh off a decent battery charger the battery read: 12.01v

Idling and at 2000rpm under load the battery read:13.8

Directly on the alternator read:13.8

Voltage drop on ground read a wooping: .70v
I cleaned some contacts and got that number drown to a more reasonable .02v

Postive voltage drop read: .21v

So it sound like alternator failure coupled with a battery gone bad.

What do you guys think?
 

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Well your battery certainly is bad, your cables need more work right through, both sides until voltage drop is within spec and your alternator is also weak. Apart from that, you're good to go!
If you publish the reults to all of the tests as below it may help. I'd start with cleaning the connections on your cables and battery terminals to get them within spec then retest. If you can't get them within spec, replace as needed until they are. Ensure you have the mod TSB 860396 incorporated into your power side that has a direct connection between the alternator and battery terminal as well as the wandering path via the starter terminal Then-
If alternator still below spec replace and repeat test.
Finally, if battery still below spec, replace that.
It's all in the sticky FAQ

1. Engine off, all accessories on for 30 seconds, then off. What voltage ______
2. Voltage across battery at idle (no electrical load____________
3. Voltage across battery at 2000rpm (no electrical load________
4. Voltage across battery at 2000rpm (everything electrical switched on) _________
5. Voltage at ALTERNATOR at 2000rpm (everything switched on)___________________
6. Voltage drop between alternator body and battery negative (YES negative). Measure at max electrical load and 2000rpm ______________ (millivolts please)
7. Voltage drop between alternator positive and battery positive. 2000rpm, max electrical load _____________
8. Check Voltage drop from Battery Negative terminal to 1st groundpoint on vehicle______________
9. Check voltage drop from 1st ground point to block__________
10. Check voltage drop from Alternator Housing to block__________
11. Voltage from alternator positive to alternator housing
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Alrightly folks the results are in from the testing. All numbers were identical at idle and at 2000ish rpm.

Under load(lights only HVAC doesn't work due to this issue) fresh off a decent battery charger the battery read: 12.01v
Probably fine - it's the charging side in the vehicle that is more to worry about if you have fairly new battery fresh off a decent charger

Idling and at 2000rpm under load the battery read:13.8
Should be about 14.1V minimum

Directly on the alternator read:13.8
Might be a sign of the Alternator on the way out, of it could just be because it's straining under load

Voltage drop on ground read a wooping: .70v
I cleaned some contacts and got that number drown to a more reasonable .02v
0.7V is 700mv The Land Rover TSB and the electrical sticky say that anything more that 120mv is too much. 0.02V is 20mv which is much better. If just by cleaning them you dropped that much, then I would keep an eye on them as there could be internal corrosion that's causing it too.

Postive voltage drop read: .21v
This is also too high. .21V is 210mv - and again the absolute MAX is 120mv. You should see as low as 30-40mv on a good charging system.

So it sound like alternator failure coupled with a battery gone bad.

What do you guys think?
My thoughts... keep an eye on the ground straps, but be prepared to replace them. If I found that kind of voltage drop on my vehicle then I would be replacing them as a matter of course.

Positive cable... Since yours is a 1996, and you're in the states it won't be Diesel - so being a GEMS engine, they are notorious for issues with the charging on the positive cable as for whatever clever reason they originally ran the positive cable from the alternator to the starter motor, and then from the start motor up to the battery. As the SM can get oily if there are leaks that drip onto it, then it can cause the cables to go horrible at the start motor, which as the charging voltage comes through that point, it affects the final voltage you see at the battery. So the charging supply has to go through about 2M of cable BEFORE it even hits the battery.

One thing I do on pretty much every GEMS vehicle I work on (I think it was actually in a TSB from LR aswell) is put an additional charging cable direct from the +ve of the alternator to the +ve of the battery, to create a shorter path to the battery, and this a) reduces the voltage drop as the cables are shorter (not by a lot probably, but cable has resistance and the longer it is, the more voltage drop you get - hence why power companies run the long distance cable at many kV) and also because it then bypasses the potential oily area of the starter motor - which over the years will get into the cables and will also degrade performance.

My first steps in your case would be:
Add an additional large gauge link between alternator +ve and Battery +ve to reduce the voltage drop you've seen on the +ve cable
Double check the ground straps and probably replace them as matter of course.

Once they are done, redo the tests and note the changes. If the alternator voltage is still showing low, then the additional load of previous bad cables have probably killed it. But with new cables, when you replace it at least you know it isn't going to be over worked!

Marty
 

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Discussion Starter #24
Thanks for the tips guys! I'm going to run that cable straight to the battery and I'm also going to clean all the positive contacts. If that fails I'll retest and go from there.
 

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I would do the changes and retest afterwards anyway - just to make sure that it has solved the problem, rather than taking it for granted that it will!
 

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Discussion Starter #26
Alright guys it's time for the weekend update.

So I ran a nice beefy cable from the alternator straight to the battery and saw an instant improvement. My battery voltage when running ran up to 14.18v and my positive voltage lost improved greatly. It's now only 3mv between the alt and the battery and is about the same from the battery to the engine compartment fuse box.

That's the good news, now for the bad news.

The problem still persists. I still have a dead dash. The only light I get is a SRS light that only shows up during the "test" time when normally all the lights turn on.

I unplugged and replugged almost all the BeCM connectors just thinking there may be a loose connection but that didn't help everything.

I really at a loss guys. Could this be a bad BeCM?

Thanks again for your help.

Edit:

I neglected to add that I also tested the voltage at the BeCM terminals. Everything there is also getting 14v+ when running.

It seems not to be a voltage issue.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Glad the charging side of things is all sorted! 14.1V is what I see on my P38 when it's charging aswell.

Re the instrument cluster issue...

It could be the BECM, yes - Do ANY of the other electrics not work? Specifically:
Ignition Barrel Illumination
Clock
Radio
Or the Front Footwell Lamps?

If any of those don't work aswell, then it could be a problem at the splice for the power feed to the instrument cluster. The instrument cluster gets 2 power feeds from the same fuse - both purple wires, on pins 4 and 14 on the cluster connector. Have you verified there is voltage there between pins 4/14 and the instrument cluster ground pins (7 and 17)?

I would check that - and if there is 12V getting there, then it is looking more likely to be either a BECM OR instrument cluster problem (the cluster has a 5V regulator on it for all the logic circuitry, which if that has failed, then that would cause issues even if there was power coming into the cluster.

I have seen a couple ok BECMs where the instrument cluster hasn't worked on them, and it's a fault somewhere in the logic board, but in both cases a load of other electronics didn't work either, and the engines wouldn't crank, yet alone start aswell.

Hope this gives a couple more things to check before leaning towards a BECM failure!

Marty
 

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Discussion Starter #28
The radio is disconnected and was like that when I bought it. The original owner had some sort of after market radio wired that he disconnected before selling the car. To wire said radio he chopped the factory harness wires. The radio has been disconnected for some time and did not present an issue.

The ignition barrel light is fine. I don't recall seeing an issue there.

The foot well lights however definitely have the same issue as the dash. When the dash does should intermittent signs of life the foot well lights flicker on and off.

Not positive on the clock I'll have to check on that.
 

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Discussion Starter #29
I'm going to try the pin outs next and well see where that goes.
 

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If you're sure that all of your connectors behind kick panel and to binnacle itselfare clean and good, the next thing to try is to substitute a known good binnacle. Careful with the mileage of the substitute though as the system will pick up the highest recorded mileage from either BECM or binnacle and you'll be stuck with it. No going back from that.
If no joy there, it is indeed looking more like a BECM problem.
 

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Discussion Starter #31
So on a whim I got to thinking about a quick way to test the theory that it may be an issue with one of those purple wires. So I stripped and connected 2 radio wires, the switched 12v(red and white) to the 12v constant(purple) wire and the dash came alive perfectly!

So that's great of course because now I don't think the BeCM has failed. So it tells me I must have some sort of issue with that 12v constant purple wire. I suppose I'll check the pin out and it's it failed i'll go from there. If it's fine i must have a bad connection somewhere.
 

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I would be checking in the RH sill below the trim. The wiring looms go from the BECM down in there, and showing on that output of the BECM there are 2 splices in the Purple wire for a LHD vehicle.

Unfortunately the wiring diagram doesn't show the location of the splices, but it should be fairly easy to find as you unwrap the tape from the loom.

I would be inspecting the splices for the purple wire to make sure one hasn't come adrift slightly and is causing your problem...

Either that or there is a fault in the output of the BECM that feeds those bits, but if the key illumination works OK, then it more points back to a wire issue as it gets fed from the same BECM output.

Good thinking on the power from the radio feed.. And even better news that the cluster came alive!

Marty
 

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You could be the second person with the same problem in a matter of days. Another owner on a different forum had a similar, but not quite the same, problem. He found that he was only getting 6-8V on the purple wire up to the dash. That wire comes from fuse 1 in the BeCM and doesn't appear to go anywhere else inside but obviously does. It emerges from the BeCM on the only connector on the back, the one that is accessible from the rear passenger footwell. He was measuring the same voltage there. I had a problem with the ignition switch supply, on the White/Red, where the connector had overheated and caused a high resistance joint. I sorted that by cleaning up and re-tensioning the connector but the problem with the purple supply appears to be a bad solder joint inside the BeCM itself. Quick and easy fix was to run a wire from one of the power feed studs on the BeCM, through a 10A inline fuse and splice that into the purple wire where it comes out of the connector.
 

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Discussion Starter #34
You could be the second person with the same problem in a matter of days. Another owner on a different forum had a similar, but not quite the same, problem. He found that he was only getting 6-8V on the purple wire up to the dash. That wire comes from fuse 1 in the BeCM and doesn't appear to go anywhere else inside but obviously does. It emerges from the BeCM on the only connector on the back, the one that is accessible from the rear passenger footwell. He was measuring the same voltage there. I had a problem with the ignition switch supply, on the White/Red, where the connector had overheated and caused a high resistance joint. I sorted that by cleaning up and re-tensioning the connector but the problem with the purple supply appears to be a bad solder joint inside the BeCM itself. Quick and easy fix was to run a wire from one of the power feed studs on the BeCM, through a 10A inline fuse and splice that into the purple wire where it comes out of the connector.
I checked the pin outs this morning and to my surprise I have the exact same issue. I'm only reading .3 volts on the pin out for the purple 12v constant line. I'm going to attempt the work around and hope that doesn't mess with anything in the BECM. I don't see why it would but you never know.
 

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I shouldn't have an effect on anything else as that line is just a permanent battery feed.

If it is damage to the track on the BECM board then they are easy enough to fix aswell. Just bypass the affected bit with a decent size piece of copper wire :)
 

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Discussion Starter #36
The BECM bypass went perfect.

For anyone with a similar issue here is what I did.

I cut the purple constant wire and soldered it to a inline fuse kit I picked up for a few bucks from the local auto store.

Then I terminated that in line fuse onto a ring terminal that I screwed onto the postive 12v post to the BECM. Be sure to insulate the end you cut so it won't short anything(not pictured).
 

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