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A Quickie For The Electricians Out There

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#1 Stimpy

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Posted 21 August 2013 - 08:28 PM

First - a very quick question.....

 

If I run a wire from IGN on the ignition switch, or any LIVE wire for that manner - then connect it to a lamp - then connect the other leg of the lamp to the centre, smaller connection of the alternator should this happen:

 

key to ACC - lamp comes on

 

start engine

 

light goes off after a flick of the revs.

 

The logic being - 'proper' live to bulb which then earths at the alternator so light comes on - engine starts and sends the same voltage back up the wire - light goes off.

 

Is that the correct fundamentals ?

 

For the moment the light comes on but when the engine starts the light goes to 'glow'.  It doesn't get brighter or dimmer relative to revs - it simply goes from bright red to a constant dim red.  Or am I being dim?  :shy:

 

The other question is - the two fat brown cables at the alternator - do they do exactly the same thing? - i.e. provide voltage to the car's electrics.  It appears to do that on my car and they go off and do the same job- therefore - why have two cables?

 

Thanks in advance for any help



#2 KernowCooper

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Posted 21 August 2013 - 10:29 PM

Ok what your doing is just making a external Ignition warning light, 12v from any feed into the lamp and out the lamp onto the IND small terminal on the alternator, no charge 12v flow into alternator and finds a earth through the diode pack, start engine and alternator starts to charge and 12v comes through the Ignition Light IND terminal and no current flow light goes out. Please be careful where you put your test light as if its not the special Ignition warning light holder which is insolated the earth of the casing holder will be live!  Your Ignition light is glowing because your alternator is not charging to its full capacity, and this type of fault usually indicates a faulty Diode Pack.

 

Put a voltmeter on the battery and see if your voltage is 13.7-14.2v

 

The 2 brown wires in the 3 wire plug.

Tthere seems to have been two variations of how the spades were used - on one the central large spade is the output and the other large spade is the battery sense terminal, with the normal-sized spade being the IND terminal,

 

Read the full Alternator Article here http://www.theminifo...or-wiring-acrs/


Edited by KernowCooper, 21 August 2013 - 10:30 PM.


#3 Stimpy

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Posted 28 August 2013 - 10:57 PM

Sorry for the lack of reply here - I haven't had time to take voltage readings, which is a pain because an entirely gutted mini interior - except wires- is somewhat undrivable.

 

I believe I did it at the time just before this thread and I'm sure the voltage was LESS at the battery terminals when I started her up. I am in no-way sure though however the volts on the meter were definitely less than 13v



#4 KernowCooper

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Posted 28 August 2013 - 11:20 PM

If the engine wiring harness is intact and wired then running at 2000rpm you should see the battery voltage rise to 13.7-14.3v, otherwise its not charging



#5 Stimpy

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Posted 29 August 2013 - 08:33 PM

Ok - figure this out (if you can!) 

 

Turn engine on (red IGN light goes from bright to dim)

 

Readings at the battery?

 

12.4 volts when engine is running

12.6 volts when engine switched off

 

Even I know that looks wrong!

 

Time to call in the professionals?



#6 tiger99

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Posted 29 August 2013 - 09:53 PM

Your alternator is not charging, so the voltage is less when the ignition is on. If you don't have the warning light connected, the alternator will not charge, as it needs to draw some power through the lamp to energise the control circuit.

 

Previously, if the lamp was still dim with the engine running, it may have been a faulty diode pack, as Kernow said, but the other possibility is a high resistance in the ignition switch or its wiring, which causes the voltage in the ignition circuit to be so low, compared to the battery, that the lamp glows due to reverse current flow. Not common, but I have seen it, and despite the reduced voltage to the ignition system, the engine still ran ok.

 

But most likely you just need a new or reconditioned alternator.



#7 Stimpy

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Posted 29 August 2013 - 10:48 PM

Your alternator is not charging, so the voltage is less when the ignition is on. If you don't have the warning light connected, the alternator will not charge, as it needs to draw some power through the lamp to energise the control circuit.

 

Previously, if the lamp was still dim with the engine running, it may have been a faulty diode pack, as Kernow said, but the other possibility is a high resistance in the ignition switch or its wiring, which causes the voltage in the ignition circuit to be so low, compared to the battery, that the lamp glows due to reverse current flow. Not common, but I have seen it, and despite the reduced voltage to the ignition system, the engine still ran ok.

 

But most likely you just need a new or reconditioned alternator.

The 'excitement' bit def happens because the light goes from bright red - then a quick flick of the fun button - red glimmer. Both 'definite' in manner.

Also - if I 'offer up' the old PCB dashboard and connected everything the same symptom happens (except with an orange light - as is the weird choice of colour).

 

You're mention of needing a recon a/nater has come to coincide with my feeling.  I just wanted others to have some form of agreement before ripping it out.

Because I've been working on the electrics quite a bit - could I have accidentally damaged the a/nator or are they hardy fellows and take some beating before hitting the floor?

 

Cheers 

Steve

 

P.S.  If I cannot find a way to make this new power steering keyless system to work then I'll need an expert so it's probably a good idea to get the local mobile chap to look at those two and also check the quality of my re-wiring work.



#8 Stimpy

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Posted 01 September 2013 - 01:26 PM

Ok....    I've done a bit more research at the alternator end.  A bit of a tangent coming up!

 

I was confusing my alternator with the one in my Stag, so.......

 

On my (mini) alternator there are (looking down at it) 2 thick brown leads and a small thin brown lead.  I assume that the thin lead wasn't a loaded one - and thus goes back to the red IGN light etc.

 

So I've uncovered the plastic sheathing from the 2 thick brown leads and they get soldered together, so the two thick brown leads are essentially one and the same.

 

So I started the engine and took readings from the alternator.

 

The 2 thick leads show just over 12 volts.....

 

HOWEVER - the small thin lead (at the bottom as you look down on the alternator) is squirting out 14.2v !

 

I carefully removed the plug to the alternator as it was running.

 

I took the readings again and it was the same as before, ie top two large spades @ just over 12v and the smaller indented spade at the bottom throwing out 14.2v.  This confuses me big time as why would the thick cables / spades show a measly 12v and the IGN light lead showing 14v.

 

I then remembered that - because the car's interior is gutted - the ammeter dial is missing.  I remember that the ammeter sits within the circuit for the car.  So - feeling hopeful - I went back to the ammeter and bridged the ammeter female connections.

Then I hooked up the voltmeter again - feeling hopeful - but the results were the same.

 

I'm at a loss why the thin IGN lead would 'prove' that the alternator is capable of giving 14v but doesn't do so at the main brown connections.

 

I'll need to re-click that link to re-read the alternator thread now my mind is tuned into the correct alternator plug leads! 

 

Any further ideas are extremely welcome :-) 



#9 KernowCooper

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Posted 01 September 2013 - 02:47 PM

Firstly NEVER TAKE THE ALTERNATOR PLUG OUT WITH THE ENGINE RUNNING,

 

A running alternator has energy stored in its field winding, and suddenly interrupting the alternator output by disconnecting the connection to the battery by removing its connection on the brown wires results in hundreds of Volts appearing at the alternator output. Since this same circuit is powering other devices, such as electronic gear, the high voltage spike can immediately destroy lots of equipment ...not the least of which is the alternator regulator.

 

 

Never test a Alternator with the plug taken out it needs to have the plug from the Ign Warning light connected as the exciter wire into the alternator and the 2 browns are connected back to the battery

 

Connect it back up and do the full test here, http://www.theminifo...or-wiring-acrs/



#10 dklawson

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Posted 01 September 2013 - 02:49 PM

First:  NEVER unplug an alternator when the engine is running.  The sudden lack of load on the output from the alternator can damage its internal electronics.  

 

Regardless of anything else you measure, focus on the voltage across the battery terminals when the engine is off and when it is running.  You should see a 1.5 to 2 V increase over the battery at rest when the engine is running.  If you don't the alternator is not charging the battery regardless of any other observations you have.



#11 Stimpy

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Posted 01 September 2013 - 07:45 PM

Firstly NEVER TAKE THE ALTERNATOR PLUG OUT WITH THE ENGINE RUNNING,

 

A running alternator has energy stored in its field winding, and suddenly interrupting the alternator output by disconnecting the connection to the battery by removing its connection on the brown wires results in hundreds of Volts appearing at the alternator output. Since this same circuit is powering other devices, such as electronic gear, the high voltage spike can immediately destroy lots of equipment ...not the least of which is the alternator regulator.

 

 

Never test a Alternator with the plug taken out it needs to have the plug from the Ign Warning light connected as the exciter wire into the alternator and the 2 browns are connected back to the battery

 

Connect it back up and do the full test here, http://www.theminifo...or-wiring-acrs/

 

 

Oops - Point taken - won't do it again!

 

I only took it off to make sure nothing else from the brown leads would influence the individual spades in the alternator - so I started the car, revved to make the IGN light go off - well - "dim" then took the connection off while the alternator was 'active' just to test the 'raw - clean' voltage coming out of the alternator.  I thought, by doing that, I had isolated the alternator from everything (except the belt).  I didn't plug it back in while the ignition was on.


Edited by Stimpy, 01 September 2013 - 07:46 PM.


#12 Stimpy

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Posted 01 September 2013 - 07:47 PM

First:  NEVER unplug an alternator when the engine is running.  The sudden lack of load on the output from the alternator can damage its internal electronics.  

 

Regardless of anything else you measure, focus on the voltage across the battery terminals when the engine is off and when it is running.  You should see a 1.5 to 2 V increase over the battery at rest when the engine is running.  If you don't the alternator is not charging the battery regardless of any other observations you have.

I've done that test - and the voltage is 0.2 volts LOWER when the ignition is on (but 14.2v at the thin lead back at the alternator).



#13 Stimpy

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Posted 01 September 2013 - 08:02 PM

Firstly NEVER TAKE THE ALTERNATOR PLUG OUT WITH THE ENGINE RUNNING,

 

A running alternator has energy stored in its field winding, and suddenly interrupting the alternator output by disconnecting the connection to the battery by removing its connection on the brown wires results in hundreds of Volts appearing at the alternator output. Since this same circuit is powering other devices, such as electronic gear, the high voltage spike can immediately destroy lots of equipment ...not the least of which is the alternator regulator.

 

 

Never test a Alternator with the plug taken out it needs to have the plug from the Ign Warning light connected as the exciter wire into the alternator and the 2 browns are connected back to the battery

 

Connect it back up and do the full test here, http://www.theminifo...or-wiring-acrs/

I've looked at that posting.  (Actually on two occasions) and it's a fine description which I can now follow (having re-looked at my alternator) ).  So my alternator is-

 

two large spades that are joined soon after the connection to the alternator (the two fat cables are soldered together under a plastic sheath).

 

...which means my alternator 'system' is pretty simple:-

 

Effectively ONE connection (from the two fat brown cables) and ONE thin cable (brown + another colour - which I think is yellow or orange).

Voltage at the battery when engine on: 12.4 v

Voltage at the battery when engine not on:  12.6v

Voltage at the thin cable when engine on: 14.2v

 

So my alternator knows how to provide 14.2v but doesn't deliver it down the fat joined brown cable - so my battery never receives a charging amount.  It's almost tempting to connect the thin cable to the fat cable to pass 14.2v to the car - BUT!!!! (before you die of shock) I would not as there is a reason why the thin cable is thin !  

It's a bloody pain in the ar*e!



#14 sledgehammer

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Posted 01 September 2013 - 08:15 PM

I would just buy a new alternator

 

& check the condition of leads , terminals , battery & earths



#15 KernowCooper

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Posted 01 September 2013 - 08:33 PM

Do the tests listed here http://www.theminifo...ng-basic-tests/

From no9 onwards will tell you exactly whats wrong with your alternator.







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