Mysteries Of Discovery 4 Electrics

[Gravy]

Well the alternator saga has me dreaming of owning a 70s Holden with a 6 cylinder red motor. How can fitting new brushes and rear bearing to a serviceable alternator reek so much havoc.

3 Episodes removing and fitting the alternator on my TDV6 including a brand new replacement unit has up to yesterday provided me with the dreaded big red battery symbol looking at me on the dash.

Lost count of the multitude of web posts on this subject until there was a gem of wisdom " Check the fine cable enclosed within a black woven sheath that is attached to the positive battery terminal".

I had previously cleaned the ring terminal attached to the battery post, however never given it a tug to ensure it was not severed. Also never had the battery positive terminal disconnected, as recommended I always disconnected the negative terminal prior to working on the vehicle.

This is where the mystery makes its appearance, the wire in my case was not severed, however along its length there are a series of sections clothed with heat shrink which are tough to flex, their purpose can not be identified.

Since flexing these Joints (????) the red battery symbol has disappeared. Engine running after cranking provides a battery terminal voltage of 14.6 or 14.7 Volts.

If anyone can explain what has happened here I would gladly offer my stripped down original alternator as a reward.

[DiscoJeffster]

That is the battery monitor which measures the current flow in/out of the battery to determine what voltage the ECU should tell the alternator to run at, based on need and time to recharge (effectively). This is to reduce load on the engine from the alternator and supposedly improve the battery health (but seemingly it’s quite the opposite as it will sacrifice the battery charging for engine efficiency).

If that things isn’t seeing the correct data because of a bad wire, then it makes sense it wouldn’t charge correctly.

What was the error code in the ECU? Did you check it or just assume an alternator issue because of the triangle?

[Gravy]

That is the battery monitor which measures the current flow in/out of the battery to determine what voltage the ECU should tell the alternator to run at, based on need and time to recharge (effectively). This is to reduce load on the engine from the alternator and supposedly improve the battery health (but seemingly it’s quite the opposite as it will sacrifice the battery charging for engine efficiency).

If that things isn’t seeing the correct data because of a bad wire, then it makes sense it wouldn’t charge correctly.

What was the error code in the ECU? Did you check it or just assume an alternator issue because of the triangle?

Thanks this confirms what my research revealed.

My Carsoft Scanner reported Error P0A1A.

My issue is what is the reason for those inflexible sections in the wire, how could removing and refitting the original alternator compromise this measurement circuitry? Alright I admit to breaking the LEN connection wire on the alternator however this was repaired, extended to make subsequent alternator removals simpler, it appears there is no finite logic to what has occurred here.

Owners have requested a means to get back to basic alternators and control circuitry, to date I have not seen a solution. I personally am a believer in "if it aint broke dont fix it" however I do practice preventive maintenance.

[Graeme]

You may have bumped the wire while removing the negative terminal, otherwise pure co-incidence.

Edit: I removed the back cover from my recently dead 220A L322 alternator to find a pair of cooked diodes and the ends of the respective field wires burnt. No sense in fitting a new diode pack.

[Gravy]

You may have bumped the wire while removing the negative terminal, otherwise pure co-incidence.

Edit: I removed the back cover form my recently dead 220A L322 alternator to find a pair of cooked diodes and the ends of the respective field wires burnt. No sense in fitting a new diode pack.

Graeme you have probably nailed it. Be nice if there was an error to identify when this circuit is compromised.

P0A1A Details as per the Service Manual

Generator Control Module -
No sub type information
Generator to engine
control module LIN
circuit, open circuit
Generator/engine
control module failure
Check for good/clean contact at
generator and engine control module
LIN circuit connectors/pins. Refer to the
electrical circuit diagrams and check
generator to engine control module LIN
circuit for open circuit. Check for
engine control module hardware DTCs
and refer to relevant DTC index. Clear
DTCs and repeat automated diagnostic
procedure using the manufacturer
approved diagnostic system
Check and install a new generator /
http://www.landrover-manuals

[BradC]

I had previously cleaned the ring terminal attached to the battery post, however never given it a tug to ensure it was not severed. Also never had the battery positive terminal disconnected, as recommended I always disconnected the negative terminal prior to working on the vehicle.

This is where the mystery makes its appearance, the wire in my case was not severed, however along its length there are a series of sections clothed with heat shrink which are tough to flex, their purpose can not be identified.

Since flexing these Joints (????) the red battery symbol has disappeared. Engine running after cranking provides a battery terminal voltage of 14.6 or 14.7 Volts.

If anyone can explain what has happened here I would gladly offer my stripped down original alternator as a reward.

Is that wire Brown with a blue stripe? If so it's the positive supply to the battery monitor module and has 2 solder joints which would likely be the heatshrink sections. According to the wiring diagram it's 1mm from the battery to a 0.35mm section and then back to 1mm before it gets to the BMS module. A dodgy solder joint would result in the "it wasn't working until I flexed it" kind of symptom.
The BMS module communicates with the BCM on a LIN bus, and that would cease if the BMS lost its supply.

Page 90 of the D4 wiring diagram 414-02 - Generator and Regulator. DV6 3.0L.

[Gravy]

Is that wire Brown with a blue stripe? If so it's the positive supply to the battery monitor module and has 2 solder joints which would likely be the heatshrink sections. According to the wiring diagram it's 1mm from the battery to a 0.35mm section and then back to 1mm before it gets to the BMS module. A dodgy solder joint would result in the "it wasn't working until I flexed it" kind of symptom.
The BMS module communicates with the BCM on a LIN bus, and that would cease if the BMS lost its supply.

Thanks for this solution

Page 90 of the D4 wiring diagram 414-02 - Generator and Regulator. DV6 3.0L.

Is there a reason behind the wire diameter changes? Is it to create a fusible link as on previous models there was a fuse in LIN bus circuit (Fuse 20).

Looks like I might have to resolder these joints to be certain the fault wont be duplicated.

[BradC]

Not that I can tell. The wiring diagram just shows 3 segments with 2 solder joints. The segment in the middle is 0.35mm.

I don't have a D4, just the wiring diagram.

My D3 is "not quite" as complex (marginally) but can still be as problematic!

[Gravy]

If you have the dreaded RED BATTERY SYMBOL making its appearance on your dash confirm the integrity of the conductor between the positive battery terminal and the Battery Monitor Module.

As has been posted this wire has two joins in it where the wire gauge undergoes changes. These joins are only crimped and the quality of the joins is poor. If there is any doubt remove the hot melt filled heat shrink, cut, strip, solder and heat shrink the wire joints.

Might save you from the grief, worry and expense I have experienced.

[Eric SDV6SE]

Is simply replacing this wire completely an option or are the gauge changes a requirement (fusible links were mentioned)

[scarry]

Well the alternator saga has me dreaming of owning a 70s Holden with a 6 cylinder red motor. How can fitting new brushes and rear bearing to a serviceable alternator reek so much havoc.

Two bolts,two wires,piece of wood to lever it to tighten the fan belt,all good.An hour going slow.[wink11]

The old V8 Rovers were pretty easy as well.

Those were the days[biggrin]

[veebs]

I had no end of trouble when my alternator was replaced. Straight swap in my case to a new one, but the error remained. Not immediately, only appeared after a 20min drive or so.

Solution in the end was a complete reset of the car - back to ‘new born’ state. Elements of the egr remap had to be reinstalled, to give an idea of the level of ‘wiping’ that went in with the ecu.

All good since…

[DiscoJeffster]

I had no end of trouble when my alternator was replaced. Straight swap in my case to a new one, but the error remained. Not immediately, only appeared after a 20min drive or so.

Solution in the end was a complete reset of the car - back to ‘new born’ state. Elements of the egr remap had to be reinstalled, to give an idea of the level of ‘wiping’ that went in with the ecu.

All good since…

Funny you say this. When my crankshaft position sensor was replaced, they couldn’t get it to go again. They too had to flash the PCM to get it to run again. Hard to understand what’s going on, but maybe some state gets retained that causes issues.

[Gravy]

Is simply replacing this wire completely an option or are the gauge changes a requirement (fusible links were mentioned)

Maybe someone who is totally familiar with the communication protocol used on this link can explain the reasoning behind this. It is beyond my level of comprehension despite using protocols prevalent in data communication applications for most of my working life.

[BradC]

Maybe someone who is totally familiar with the communication protocol used on this link can explain the reasoning behind this. It is beyond my level of comprehension despite using protocols prevalent in data communication applications for most of my working life.

There is no communication on that wire. It's the positive supply for the BMS. I can't explain why they'd do it that way.

The LIN wire goes from the BMS to the BCM. LIN is a simple open-drain, single wire, bi-directional serial protocol. The devices (one or more) have a pull-up resistor that pulls the LIN wire to 12V, and they assert the bus by pulling it low (transistor or MOSFET usually). When they relinquish the bus, the combined pull up resistance pulls it high again with the time constant of the combined resistance and the capacitance of the bus. It's simple and robust, but as it relies on a passive pull-up it's not particularly high speed.

[Eric SDV6SE]

There is no communication on that wire. It's the positive supply for the BMS. I can't explain why they'd do it that way.

The LIN wire goes from the BMS to the BCM. LIN is a simple open-drain, single wire, bi-directional serial protocol. The devices (one or more) have a pull-up resistor that pulls the LIN wire to 12V, and they assert the bus by pulling it low (transistor or MOSFET usually). When they relinquish the bus, the combined pull up resistance pulls it high again with the time constant of the combined resistance and the capacitance of the bus. It's simple and robust, but as it relies on a passive pull-up it's not particularly high speed.

No idea what you said, but sounds like a good explanation.

[BradC]

No idea what you said, but sounds like a good explanation.

Are you old enough to remember the leather ropes that ran the length of the bus? You pull down on the rope to ring the bell and let the driver you want to get off.

It's a lot like that. The rope has a spring (the resistors that pull the bus up to +12V). Any device that wants to signal pulls the bus down. It doesn't matter if one or 4 do it, the result is the same. The bell rings once.

Now picture it as the driver calls out the seat numbers in turn. Seat 1, seat 2 and so on. When he gets to a seat number that wants to get off they pull the rope. In a LIN scenario there is one master and one or more slaves. The master calls out the slave addresses in order and if a slave has something to say it pulls the rope.

Now we complicate it in that the master talks to the slaves by pulling the same rope. It's still just a rope on a spring, and there are only 2 states. Pulled and not-pulled. The LIN bus is the same. It's either pulled up to +12V or down near ground and the threshold is half way. Is it above 6V or below 6V.

[Eric SDV6SE]

Are you old enough to remember the leather ropes that ran the length of the bus? You pull down on the rope to ring the bell and let the driver you want to get off.

It's a lot like that. The rope has a spring (the resistors that pull the bus up to +12V). Any device that wants to signal pulls the bus down. It doesn't matter if one or 4 do it, the result is the same. The bell rings once.

Now picture it as the driver calls out the seat numbers in turn. Seat 1, seat 2 and so on. When he gets to a seat number that wants to get off they pull the rope. In a LIN scenario there is one master and one or more slaves. The master calls out the slave addresses in order and if a slave has something to say it pulls the rope.

Now we complicate it in that the master talks to the slaves by pulling the same rope. It's still just a rope on a spring, and there are only 2 states. Pulled and not-pulled. The LIN bus is the same. It's either pulled up to +12V or down near ground and the threshold is half way. Is it above 6V or below 6V.

Cheers for the "real world" clarification Brad.

[coopers1969]

does anyone know where i can get a replace connector for the back of the alternator i think it is the LIN plug i snapped the wire right at the ceonnector and can't solder it. it is a denso alternator that i have purchased. i have spent over 2 hours looking for the part but can find it any where.

[Gravy]

does anyone know where i can get a replace connector for the back of the alternator i think it is the LIN plug i snapped the wire right at the ceonnector and can't solder it. it is a denso alternator that i have purchased. i have spent over 2 hours looking for the part but can find it any where.

If you have the correct pin removal tool you should be able to remove the socketed pin, prise open the insulation crimp and solder on to where the wire proper is crimped.

I have just been thru this exercise however I was fortunate that there was a small amount if wire protruding from the back of the plug. After repairing the connection, heat shrinking it, I then made a mold attached to the back of the plug and filled it with Araldite.

So you dont duplicate the break attach a 300mm length of wire with a male crimp connector attached. The PITA is to extend the existing broken connection wire by soldering a 400mm length of wire to it with a compatible female crimp connector attached.

This process means you can leave the wire connection to the Lin plug undone until you have the alternator bolted in.

I did a similar modification to the B+ wire, fitting a join in it, made removing and installing the alternator simple as there are no connectors on the alternator to undo. Land Rover should have done this when they designed and built the D4s with twin turbos.