Battery light flickering

[e635815]

Guys,
I have got my battery light flickering when the engine is running.
The battery itself is brand new, I have checked the voltage at the alternator + cable (+18V) and verified that I have the same at the battery end when the engine is running.
Of-course the 100A isn't broken (tested) therefore the battery is being charged by the alternator.
What could be the reason for this indicator flickering? Where does the light take its signal from?
Any pointer as to what shall I check and measure on my circuit?
Thanks for the help.
Regards
Philippe

[geordiepingu]

+18V?! Should be more like 14.5V at most. Sounds like your regulator on the alternator is packing in. The light connects to the regulator.

[e635815]

Now that you are talking about it, +18V seems a bit high indeed.
Does anybody know where can I buy a replacement regulator? Don't want to change the alternator if it isn't needed.
Thanks

[Polly Grigora]

e635815 said:

Now that you are talking about it, +18V seems a bit high indeed.
Does anybody know where can I buy a replacement regulator? Don't want to change the alternator if it isn't needed.
Thanks

Short circuit regulator gives 18 + volts output and maximum alternator current output at the same time, it doesn't cause the warning light to flicker

Flickering warning light is often caused by worn brushes, damaged diodes or stator windings

Worn brushes would prevent alternator from over-charging even if the regulator has gone short circuit - Very doubtful brushes are worn out as alternator would go off charge rather than over-charging (18 volts)

When alternator is over-charging it over-heats and eventually its stator windings burn and its diodes fail

There is a very good possibility that your alternator has a faulty regulator that has burnt the rest of it out

The new battery will now have buckled plates if its been over-charged to a state of very hot to boiling point

[geordiepingu]

Ebay have replacement regulators, the unit replaces all of the bushes in one go too quite simply. My opinion though is to just replace the alternator or send it away to be refurbished for peace of mind if the car is 20+ years old, as the bearings will be quite old too and will be the next failure point.

AMR4247 is the Land Rover part for the 100A alternator assembly for V8 Serpentine onwards. I tend to supply folks with the 'G' suffix ones (AMR4247G), which tend to be Land Rover OEM equivalent parts.

[e635815]

Thanks for your thoughts. I concur with you and a new alternator is on its way.
Now regarding the connections. I might have another issue there.
So, the thick brown cable is the +14,7V output to the 100A fuse.
And the brown and yellow wire with the captive nut, what does it do? When the battery is connected but not the alternator (as it sits on the bench at the moment), am I supposed to see +12V at this connection?
Finally, the wire with the spade connector, this is the signal to the dash battery light. This should be a +12V output when the alternator is running, right?

I have checked today and this is what I have (alternator disconnected):
- brown: +12v
- brown/yellow: 0v
- white spade connector: 0v

Thanks
Philippe

[Polly Grigora]

Heavy Brown - B+

Thin Brown/Yellow - D+ Warning Lamp

[e635815]

ok, then, the warning lamp only sees +12V when the alternator is delivering. Which isn't the case now.
And what about the tacho drive? Where does this lamp connect to? What is it driving? The tacho reading is taken from the megajolt in my case.
What is therefore connected to this wire?

[Polly Grigora]

e635815 said:

And the brown and yellow wire with the captive nut, what does it do? When the battery is connected but not the alternator (as it sits on the bench at the moment), am I supposed to see +12V at this connection?

With the alternator on the bench and stationary

Battery positive jump lead connected to B+

Battery negative jump lead connected to alternator body

There will be approximately 12 volts negative at the D+ terminal (Brown/Yellow battery warning light cable connection)

When the alternator is charging, D+ will output 12 volts + and extinguish the battery warning light

e635815 said:

Finally, the wire with the spade connector, this is the signal to the dash battery light. This should be a +12V output when the alternator is running, right?

No this isn't correct

The W terminal with the spade connector is a single phase tapping directly from one stator winding

W single phase AC output is sometimes used to drive tachometers in diesel powered vehicles and it isn't very accurate

[e635815]

Waoooo… got my questions answered… almost.
The spad connector side is connected to what exactly ? The tacho on the Chimaera is driven by the coil. So what exactly is this wire doing ? Can it be left unconnected ?
Thank you anyway a thousand times for all these infos.

[Polly Grigora]

There could be a spare wire in the loom that some people connect to the alternator W terminal by mistake

What colour is the wire that was connected to the spade @ the W terminal?

[Belle427]

From memory brown/yellow is charge warning and the other one is not used, can’t recall the colour sorry.
Believe it’s just in the Range Rover loom for other models, maybe Diesel engines variants for tach signal?

[geordiepingu]

Belle427 said:

From memory brown/yellow is charge warning and the other one is not used, can’t recall the colour sorry.
Believe it’s just in the Range Rover loom for other models, maybe Diesel engines variants for tach signal?

The Discovery V8 uses this for the tach signal if memory serves. Also Morgan Plus 8s with VDO instruments (like a 1 year wonder in '99).

[Polly Grigora]

e635815 - Did you get the job sorted?

[e635815]

Nope, not yet. Thanks for asking.

A new alternator is on its way. I have replaced the crimped connections on the two small wires (brown/yellow and white) not knowing that the spade connector one would not be used at all.
Nevermind.
As soon as the alternator reaches my garage, it will go straight in.
But then I need to fill-in my cooling circuit prior to any attempt at re-starting the engine.
More news to come.
Philippe

[Polly Grigora]

Very good then

e635815 said:

I have replaced the crimped connections on the two small wires (brown/yellow and white) not knowing that the spade connector one would not be used at all.

The White cable will probably have a Grey trace

White/Grey is the cable used to drive a diesel vehicle tachometer, this is the cable that many connect to the W terminal by mistake

[Oldred_V8S]

Polly Grigora said:

e635815 said:

And the brown and yellow wire with the captive nut, what does it do? When the battery is connected but not the alternator (as it sits on the bench at the moment), am I supposed to see +12V at this connection?

With the alternator on the bench and stationary

Battery positive jump lead connected to B+

Battery negative jump lead connected to alternator body

There will be approximately 12 volts negative at the D+ terminal (Brown/Yellow battery warning light cable connection)

When the alternator is charging, D+ will output 12 volts + and extinguish the battery warning light

e635815 said:

Finally, the wire with the spade connector, this is the signal to the dash battery light. This should be a +12V output when the alternator is running, right?

No this isn't correct

The W terminal with the spade connector is a single phase tapping directly from one stator winding

W single phase AC output is sometimes used to drive tachometers in diesel powered vehicles and it isn't very accurate

Useful info except one correction, the item in bold should be ground. Were it to be "12v negative" your warning lamp would be getting a 24vdc supply.

The way this works is, with the key on but the engine off, 12v is fed to one side of the warning lamp. The other connection to the lamp is grounded through the alternator, completing the circuit and illuminating the lamp.

When the engine is started and the alternator is working properly, the warning lamp wire previously grounding your warning lamp, is energized, so that the lamp is receiving 12 volts from both sides. As a result, there is no ground circuit, so no completed circuit and, therefore, the lamp does not illuminate when the alternator is charging.

[e635815]

Ok, new alternator delivered today, fitted, tested and all is working perfectly.
Except for the battery light on the dashboard (well the speedometer to be precise).
It could be a blown bulb or something else.
Does anyone know which wire color brings the battery signal to the light?
When ignition is on but engine not turning, I should see the light on since the battery delivers 12V and the alternator frame attached to the brown/yellow wire is grounded. But I see nothing, no light.

In case it is a blown bulb, it seems that I need to open the speedo to change it, right?
Thanks for the expertise.
Philippe

[Belle427]

Ignition feed to lamp is green.
As you say with ignition on lamp should be grounded by the brown/yellow cable.

[e635815]

Stupide me. The whole harness was disconnected for tracing wires back and forth. Hence the light which wouldn’t receive anything at all.
Now reconnected and everything works as supposed to.