Help - Battery light illuminated !

[RogerT]

quote
4th I checked the alternator blue terminal output + to the battery - = Only 12.6v

Yet I read that on 11th Nov you were getting 14v... Confusing

I wrote in my earlier post that I wondered whether you had the blue wire connected to the wrong terminal, as there is also a feed that goes to the rev counter if you have one, as well as the oil pressure warning system. I black wire I think? ** checks** no a thin red/black. And I wrote that I wondered if your blue wire was connect d to the wrong terminal? And then I thought that was a stupid suggestion born out of too much ignorance, so I deleted that sentence. Might still be. Someone will say...

But you could try it, and if you haven't got the red black wire you could start to wonder about your oil pressure warning system (sorry...)

[craigy345]

quote
4th I checked the alternator blue terminal output + to the battery - = Only 12.6v

Yet I read that on 11th Nov you were getting 14v... Confusing

I wrote in my earlier post that I wondered whether you had the blue wire connected to the wrong terminal, as there is also a feed that goes to the rev counter if you have one, as well as the oil pressure warning system. I black wire I think? ** checks** no a thin red/black. And I wrote that I wondered if your blue wire was connect d to the wrong terminal? And then I thought that was a stupid suggestion born out of too much ignorance, so I deleted that sentence. Might still be. Someone will say...

But you could try it, and if you haven't got the red black wire you could start to wonder about your oil pressure warning system (sorry...)

Roger,

Yes you are correct I did measure it on the 10/11th Nov then I was getting 14v (same as the battery at the time)
I can't explain why? Im sure I didn't do anything wrong then.

What i can say following the great advice on here; I have established that the light goes out if i disconnect the blue lead and connect it to the battery + terminal.
So the wiring to dash appears correct.
This led me to re-check the volts at the blue Alt D+ terminal and thats when I now noticed the difference in v?

You can see the Alternator connections in my early post pic.

The red + cables to the + terminal.
The blue cable to the D+ signal bolt terminal
Red/Black to another terminal - spade (I assume this is the rev counter) - Yes I have a rev counter fitted.
No connection to the spade + terminal next to D+ bolt terminal (seen in latest pic)

Don't think the the blue cable is connected to wrong terminal (wiring diagram says D1 and this is a screw/bolt terminal) others apart from main + terminal are both spades?

thanks for your help?

Any ideas anyone?

[Oldiebut goodie]

No connection to the spade + terminal next to D+ bolt terminal (seen in latest pic)
Any ideas anyone?

This is for a capacitor for cutting down rf noise. I have a cap connected to that terminal on my boat alternator - not many alternators have the terminal and the capacitor is internal.

[Oldiebut goodie]

Like this one:

[craigy345]

Like this one:

Thanks OBG

That is helpful.
I am now wondering way there is a D+ terminal? on the alternator.

My D+ terminal (with the blue signal wire for the dash led) seems to be putting out less v than the main terminal?
Causing the light to flicker and shine dimly.

Does it matter if the blue wire is disconnected and put onto the main alternator terminal?
(Or will this mean the light will never come on as it will also be the same as battery voltage due to the live feed from battery?)

Sorry about the stupid questions - just trying to work it out and find a solution.

Thanks

[Smiffo]

Like this one:

Thanks OBG

That is helpful.
I am now wondering way there is a D+ terminal? on the alternator.

My D+ terminal (with the blue signal wire for the dash led) seems to be putting out less v than the main terminal?
Causing the light to flicker and shine dimly.

Does it matter if the blue wire is disconnected and put onto the main alternator terminal?
(Or will this mean the light will never come on as it will also be the same as battery voltage due to the live feed from battery?)

Sorry about the stupid questions - just trying to work it out and find a solution.

Thanks

Won't the main alternator connection be permanent live as apposed to only live when the engine is running?
If so, that would mess up any split charge relay setup you have, effectively always using the leisure and standard battery at the same time and drain both when parked etc...

[Oldiebut goodie]

Take a look here - you will mess up your charging voltage if you do that.
http://www.smartgauge.co.uk/alt_mod.html

[Oldiebut goodie]

I feel that you are worrying unnecessarily - the flickering light is only showing that there is a potential difference across the bulb/led resistor. This may well be solely due to lower voltage at the dashboard end rather than a perceived problem with the alternator output and/or regulation. Easily checked by checking for a voltage difference - check volts either side of the bulb. We all know what volts are lost between the alternator and the dash end with the aged wiring that is past its best and was only just adequate upon construction.

[craigy345]

I feel that you are worrying unnecessarily - the flickering light is only showing that there is a potential difference across the bulb/led resistor. This may well be solely due to lower voltage at the dashboard end rather than a perceived problem with the alternator output and/or regulation. Easily checked by checking for a voltage difference - check volts either side of the bulb. We all know what volts are lost between the alternator and the dash end with the aged wiring that is past its best and was only just adequate upon construction.

Thanks for your reply OBG and Smiffo,

Yes having read your replies etc..
You are clearly right and now I understand I can't move the blue wire from the D+ connection as rightly pointed out this would be permeant live and also balls up the split charge system/effectively connecting both batteries.
I have learnt more how the system works ta.

OBG, the issue I don't think is in the wiring to the dash (although this could also be a contributing factor?)
The main issue I think is that I am receiving approx 1 to 1.5v less output at the D+ (blue wire) to the main battery charge output on the alternator.
Is this normal? and would that be sufficient difference to light the dash bulb?

Would anybody mind checking their voltage output at these 2 points and confirm for me?

OBG, I know you are correct that I am probably over worrying as the alternator is charging the battery with sufficient voltage but this seems such a stupid fault Im determined to rectify and learn along the way if possible?

Thanks for all your help.

[Oldiebut goodie]

It doesn't matter what the voltage is on the blue wire as far as the alternator is concerned - its secondary purpose is to tell the voltage regulator what to output after supplying the excitation voltage at start up.
To get the light to extinguish you must have the same voltage either side of the bulb, you have an inequality there, hence my saying that that is where to check the potential difference first. I would say that the most probable cause of the lower voltage at the terminal is a failing diode on that part of the circuit in the alternator.

[craigy345]

It doesn't matter what the voltage is on the blue wire as far as the alternator is concerned - its secondary purpose is to tell the voltage regulator what to output after supplying the excitation voltage at start up.
To get the light to extinguish you must have the same voltage either side of the bulb, you have an inequality there, hence my saying that that is where to check the potential difference first. I would say that the most probable cause of the lower voltage at the terminal is a failing diode on that part of the circuit in the alternator.

Thanks OBG

Will drop the dash facia out and check difference at the bulb end as you originally suggested.
Im assuming if a diode is failing or its something else internal within the alternator I will need to take out the alternator and get it referred or change the alternator?

Thanks

[Oldiebut goodie]

Re-reading the saga and it appears that you have measured two differing voltages on the terminal - the 12.6v and 14.2v, I am wondering exactly how you are measuring the voltage, ie where are you placing the negative probe when measuring? And - are you using the same reference point each time? Just that you may be having an earthing problem which could explain the illumination and the focus of attention has been on the wrong area.

[craigy345]

Re-reading the saga and it appears that you have measured two differing voltages on the terminal - the 12.6v and 14.2v, I am wondering exactly how you are measuring the voltage, ie where are you placing the negative probe when measuring? And - are you using the same reference point each time? Just that you may be having an earthing problem which could explain the illumination and the focus of attention has been on the wrong area.

As my van is a diesel (JX) the battery is in the engine bay next to the alternator.

Using either of my 2 meters (just to confirm that wasn't at fault!)
I have put the - lead directly onto the battery negative.
Then I have checked in turn the 2 different + terminals (the main alternator + and the blue wire D+ terminal) both directly at the terminal points of the alternator

I have done this both at idle and with increased revs and noticed the difference?
(I rechecked it again today following your previous post and again found the same difference?)

Thanks for taking the time to re-read this sorry saga

Much appreciated.

[Oldiebut goodie]

It is worth checking the terminal whilst the negative meter probe is held on the alternator body and see if there is any improvement - if there is there is a problem with your engine earth. Something that us 'old hands' would do without thinking about it much and so tends to get missed in trying to get over how to test various connections.

[craigy345]

Ok thanks will try that.

I made sure the battery main earth strap and connection was all clean, or do you mean another engine earth that I need to check?

Thanks