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OK, just wanted to make sure you had checked with the light on, as your light was intermittent. Good luck with the install.
 

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Discussion Starter #22
Thanks Dave...I'll update when I get it done...
 

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Discussion Starter #23
Update.

Installed the Ebay rebuilt alternator today. All was good for about 20 minutes, then every light in the car came on and every warning. Suspension, trans failsafe, HDC, ABS...I could keep going, but I think you've got the picture.

Checked the voltage and it showed 15.5v at idle. That is 1 volt higher than the max limit is supposed to be. I reved the motor and it went to over 20volts. Bummer. I will be quite upset if this rebuilt alt fried all my systems. Not to mention, I'm out 2 hours and 2 gallons of antifreeze. I emailed Highampspecialist at Ebay to see what he has to say. In the mean time, I'm still back to square one.

That means $2800 for an OEM, or $440 for an aftermarket new. I still do not know why my original alternator charges fine but shows a light. I may re-install it tonight and see if the light still comes on...which will give me a chance to check all my systems.
 

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Highampspecialist
A little too much irony in the name.

Seriously though, that sucks. Hope they make it right, and that nothing else is toast. I've seen 18-19v for a little while on these without causing any other issues.

What brand was the part?
 

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Discussion Starter #25
Hey Dave. I appreciate your support as I work this issue out!

The replacement part was the original BMW alternator rebuilt. I went this route, fully realizing, that it may only last a year or so. But my thought was that I could later rebuild my own alternator so it's up to my standards. Kinda backfired, but I can't be upset, as it was my own fault for going with the absolute cheapest alternative. You get what you pay for.

Anyway...back to business. I swapped the original alternator back in. I decided the 2 hours work was worth my piece of mind, as I would not be able to sleep until I knew all the computers in the car were alright. The good news...all is good. Well, with the exception of the charge light. No fried computers. Wheew!! I had hoped that maybe removing the original and cleaning all the contacts would solve the light, but no luck.

I went through a complete test of the original alternator. The thing works fine. I just don't get it. I can load the car with every electric load possible, and the lowest the voltage it puts out is 13.94v, for just a second or two before the idle raises and it goes right back to 14.16 volts. I try to shock it by revving the engine as fast as I can from idle to 5000 rpm under full load...and it holds absolutely steady at 14.16 volts for the whole way up and back to idle.

I am going to live with the light for a while, as I really don't think the alternator is bad. The only interesting coincidence I found through all this is the replacement alternator worked fine for about 15 to 20 minutes before it went Rambo. The original alternator always works fine for 15 to 20 minutes from a cold start before it starts to flash the light. Shortly after, the light remains on steady after a few flashes. That leads me to believe the problem has to be heat related. The light only comes on after everything is warmed up. Don't know what it means, but it's gotta mean something!?!

For anybody else reading this...I bought the fan clutch removal tools while getting ready for this job. I HIGHLY recommend anybody that owns one of these cars purchase them. I paid only $64 online, but it speeds any work at the front of the engine immensly. Changing my radiator last year I spent hours trying to remove the fan, and finally gave up and scratched myself bloody working around the shroud and fan in place. With the right clutch tools, it takes one minute and the fan and shroud are out of your way. That is not an exageration...only one minute! Don't wait...buy them before you need them!!
 

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Try disconnecting the small connector on the alternator, and see if the light still comes on after driving.

Heat could have something to do with the wiring, and if the feed from the IP (through the ECM) shorts out to ground, the light will turn on.
 

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Discussion Starter #27
I'll give that a try in the morning...I was actually planning to test those 2 wires as my next step.

I've been sitting here studying the RAV for some clue. I did find one interesting statement in the description of the instrument pack. In the chart listing the trigger for the charge light, it says "hard wired or via CAN". Interesting...If it can get the trigger from CAN, then could it be possible that some other control module is loosing its voltage input and sending the IP a trigger signal via the com bus?
 

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I have never seen the CAN turn the light on, and I've had trucks with less the 12v while running at the ABS due to corrosion. I think you're most likely looking at either a voltage drop in the power feed to the alternator, from fuse 5, through the diode, or a short in the feed wire from the IP.

Both of these should be simple tests once the connector is removed, however, the light should not turn on with it removed, so knowing when to hook up and test is going to be tricky, if you pull the connector before starting, and it is in a tough spot to get to safely while running.
 

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Discussion Starter #29
Highamp says he will swap out the Rambo alternator if I send it back, so that's one problem solved.

It will be this weekend before I get a chance to work on the small connector wires. I was going to try to do it this morning, but decided I don't want to feel rushed before work.

The diode in the blue feed wire is an interesting thought. I would give anything for an internal circuit diagram of the alternator, ecm, and IP. It's frustrating not knowing how the blue wires are used. For example:

1) Why do you need a diode in the #5 fuse wire? The alternator output cable back feeds the fuse anyway, and there is no relay to generate a voltage spike, so does the #5 blue exceed generator output voltage during operation?

2) Is the signal blue wire from the alt to the ECM an on/off signal, or is it just the alternator output voltage? Does the ECM modiy this signal before passing it to the IP, or does it just monitor it and pass it straight through unalterred?

3) Why are both wires the same color? Are they connected internally in the alternator?

Many more questions that a simple circuit diagram would answer.
 

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I believe the diode is there to prevent feedback when the ignition is not on, as that fuse is a switched circuit, and you might get stray voltage through the alternator when not in use.

The wire to the ECM is a pass through, unaltered, just internally bridged to the feed from the IP.

The wires should be different colors, ignition power from fuse 5 Green, and charge light ground side from the IP Blue.

The IP puts power to the charge indicator, which is then fed to the ECM, passed through via internal bridge, and to the alternator on the blue wire(pin 2). If the ignition feed from fuse 5 to through the diode on the green wire is deemed to be lower then acceptable voltage by the alternator, it will ground out the green wire, illuminating the charge indicator in the IP.

The green wire is also used for excitation of the windings at low rotor speeds, but is self exciting when at normal running speed.
 

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Discussion Starter #31
Thanks Dave...that makes sense. Had some time, so here are the results of some checks I did today.

1). I disconnected the small connector from the alternator and started the car. The charge light remained off, but the alternator had zero output.

2). I connected the connector, and the alternator began putting out 14.16 volts and the charge light remained off.

3). Disconnected the connector again with the engine still running. Alternator output remained at 14.16 volts and charge light off. I checked the voltage at the open connector, and one wire showed zero (switch wire), and the other showed 12.7 volts (which accounts for voltage drop across the diode for the switched wire).

4). I shorted the switch wire to ground and the charge light came on. Removed the ground and the light went back out.

5). Reconnected the connector. The charge light came on, but alternator output stayed at 14.16 volts.

My conclusion is that all seems to work as it should, except for the internal switch within the alternator. It trips with temperature instead of voltage output for some reason.

I guess my next step is to exchange the rebuilt alternator with Highamp and try it again. Hopefully I'll have better luck with it this time. If I can get the car running right on another alt, I would love to crack open my original to see what's going on inside.
 

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If you only had 12.7v at the ignition feed to the alternator, this is your issue.

See if you can just return the bad one you bought, and you need to check for and fix the voltage drop from fuse 5 to the alternator connector.
 

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Discussion Starter #33
I'll try jumping that pin direct to battery to see if it puts the light out. Do you know where the diode is located? This would be the only thing I can see that would give a voltage drop in that wire.
 

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Discussion Starter #34
I found a more detailed reference to the blue wire to the alternator. This is out of the electrical manual.

"When the engine is cranked, the alternator (C0053) supplies the ECM (C0606) a Pulse Width Modulated (PWM) signal on a U wire. The ECM uses this PWM signal to calculate the electrical load on the alternator, and controls engine idle speed accordingly."

This is interesting, as it means the blue wire at the alternator sends a pulsed signal to the ECM to control idle speed. It is not a simple "on" or "off" signal. I know from grounding this wire that it also acts as an input to the charge light. The system is much more complicated than I first thought. I thought the alternator sent a simple voltage reference to the ECM, but it turns out it is an encoded message!

I still cannot find the location for the G126 diode located along the fuse #5 green feed wire to the alternator. I have it narrowed down to somewhere between connector 0448 in the engine electronics box and the alternator.

My best guess now is the diode G126 is failing when hot, or the alternator signal processor is bad. I'll still start by bypassing the diode to see if that solves it. If not, it's back to the alternator...
 

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This may sound strange, but RAVE isn't always right, and I believe the above is one of those situations.

If the alternator pulsed on that wire, the charge indicator would be lit, either dimly or flicker, depending on the pulse width.

That wire is internally bridged from where it enters the the ECM to where it leave and goes to the IP. Look at the circuit under Engine Management. This is also describe in the internal release BMW SIDs. The ECM does not get a feed from the alternator at all, the HVAC head is what controls power management, and will send the ECM the request for idle up to increase output.

I have never stripped down the entire harness, it all goes through the rubber tubing, and gets real tight to access without damaging everything. Try a bypass, if you have a simple switch handy, might want to wire that in just in case you end up backfeeding voltage to the ignition circuit. If that cures the issue, a standard 3A diode should be fine, as you shouldn't have much current going in either direction.
 

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Discussion Starter #36
So bypassing the diode it is! I'm hoping it ends up being located in the engine computer box to make it easy on me. I also went through all the circuit diagrams. It seems G126 is just a generic designation for a diode, as I found at least 3 G126's in the car.More to follow...
 

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Discussion Starter #37
Well, bypassing the diode accomplished nothing. The light remained on. The power side of the diode had 14.16v going to it...and the diode apparently dropped it down to 12.76v. This is about typical for voltage drop across a diode that I have experienced. But putting the full 14.16v to the alternator was a bust.

So, I replaced the alternator. All is good now! I got an Ultima rebuilt from O Reilly's for $399, plus a $70 core. I decided to blow off going through the trouble of sending Highamps broken one back, so I gave it to O Reilly's as the core. I will rebuild my old alt when time permits. The new (rebuilt) alternator shows 14.24v. I find it hard to believe the car is so picky that .08v lower triggers the light...but it seems to be that picky. All I know is it works, and I can move on to other things.

Summary:

1) The cheapest rebuilt alternators are on Ebay, for about $189. I recommend avoiding them for many reasons. They painted the alternator, and I can only imagine what a bunch of flaked off paint floating around your cooling system will do. They even painted the o-ring seal. Mine lasted 10 minutes.

2) You can buy an aftermarket new alternator from multiple sources for between $400 and $800. They are all the same, so go for the cheapest if you go aftermarket new. I do not know the reliability of these. The OEM costs more than the car is worth, so don't bother checking.

3) O Reilly's has a decent rebuilt alternator for $399, and it even comes with the seal. It was so good looking that I thought they had painted it too. After trying to blast the paint off, it turns out they did not, it was just rebuilt really well...bonus!

4) Buy a set of fan clutch removal tools. They consist of a 37mm thin open end wrench, and a bar with holes in the end to lock onto the fan bolts. YOU WILL NEED THESE FOR ANY FRONT ENGINE WORK YOU DO! So buy them now. Shop around, and you can find them for about $65. They are standard to all BMW 4.4L engines.

5) You need 1-1/2 gallon of antifreeze and 1-1/2 gallon of distilled water to change the alternator. This is if you save what you can drain out the radiator valve. If you don't save any coolant, you need 2 and 2 gallons. There is no way to save that 3 gallons, unless you have a bucket to go under the entire engine.

6) Other tools: 10 mm socket to remove the skid plate, the battery cable, and the 6 alternator bolts. 13mm sockets to remove the 2 belt tensioner bolts. 17 mm open end wrench to remove the primary alternator cable and to adjust the belt tensioner. Phillips screw driver to remove 2 screws covering the front of the skid plate. Blade screw driver to remove the radiator hose clips.

7) Supplies: Dialectric grease or vaseline for the coolant hose o-rings. Anti seize for all bolts that go into aluminum, which is...all of them! New seal for alternator if it is not supplied with the new/rebuilt one.


That's it...

I'll post back if this alternator dies. If anybody else has experience with a replacement alternator, it would be nice to know...


Cheers
 

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Discussion Starter #38
Well resurrecting my old thread, as the alternator crapped out again.

Funny, last time it confused me as the charge light came on, but the alternator was still charging. This time it was the complete opposite...no charge light came on at all, until the battery discharged to the point the dash lit up like a Christmas tree. Truly, every light and every message chat can be displayed WAS displayed! I knew I was in trouble when I went to roll up the window and it only went up 2 inches and stopped for ack of power! We hobbled the 5 miles home...praying the battery would hold out. At every stop light more systems went out...tranny went to 2nd gear fail safe. Suspension locked up...light flashing...it was quite the 5 miles!

So, just wanted to update. Our alternators can fail with a light, fail without a light, and get a light and still work. Go figure.

The good news, My $400 OReilly's alternator is lifetime warrantied. All I am out is the 3 hours and more blue antifreeze!
 

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Did you find a permanent fix? I'm experiencing the same problem and I'm frigging stumped (intermittent charging system fault, voltage is anywhere between 12.x to 14.7 volts while driving, on 2nd alternator and fuse box, on my 7th or 8th battery so far, etc.)

Sent from my SM-G955U using Tapatalk
 

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I know this thread is very old but posting to it as a follow on as there was no resolution in 2016 - 2018. It is now August 2020.

I am also experiencing this on my 2006 L322 with the Jag 4.4L engine last few weeks. Events are:

1. BATTERY FAILURE?
About 4 weeks ago, battery went dead overnight; battery was about 4 years old. I merely replaced it without any analysis assuming that it had reached end-of-life. New battery is the biggest capacity Durolast that would fit - I think it was an H8 size.
Recharged old battery and it held charge at 12.6V for next few weeks. Puzzled about why it went dead overnight.

2. ALTERNATOR FAILURE?
Drove the car without issue for 3 weeks, then suddenly the battery light came on while driving. Stopped the car, turned off engine, cycled the door locks to reset computer system and re-started the car. Battery light extinguished after start and remained off for about 30 seconds then came on again. Played with it for a few cycles and it would always extinguish after starting then come back on within a few minutes and then go off for a few minutes before coming on again. The intervals were varied and unpredictable seemingly unrelated to engine speed, power delivery, road speed or electrical load as I tried all these variables.

3. NEW ALTERNATOR
Ordered a Denso remanufactured alternator from Autozone and installed it over the next 2 days after the battery light first came on.
Before removing the old alternator, I checked the voltage at the battery before and after starting the engine. Before starting, voltage at battery terminals was 12.6V; after starting, voltage at battery terminals jumped to about 13.4V. The voltage varied varied from about 13.2V to 13.8V and never went below 13.2V.
After installing the remanufactured alternator; I started the car - same behavior as before. Light extinguishes after startup then cycles on and off. I installed a voltmeter on the cigar lighter to get real-time voltage readings as I drive along.
Battery seems to be charging OK, charging voltage never goes below 13.2V but it seems to max out at about 14V. The light seems to come on at about 13.5V or lower and extinguish at about 13.7V and higher.

4. DEFECTIVE ALTERNATOR?
Hard to believe old alternator and remanufactured one are defective in exactly the same way.

HELP, PLEASE.
 
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