Alternator Wiring 3 blade connector

[jetzi]

I have such a mental block about alternator wiring, I have read the page on @Tony Brooks site about alternators but I am still struggling to understand!

 

My current alternator has only one cable connected - a big stud for battery positive. My current alternator doesn't fit the bracket well and the pulleys are out of alignment. As a result it chews up belts quite regularly.

 

I recently bought a spare (this one: https://www.ebay.co.uk/itm/LUCAS-A127-TYPE-ALTERNATOR-LEFT-HAND-LH-12V-75AMP/324193353273 ). I'm experimenting with installing this alternator, which fits the bracket much better. The intention is to then try to clean the rubber dust out of the old alternator and reposition the pulley while the new alternator keeps me going. But also I would like to have a working spare available in case my current alternator burns out!
 
The new alternator has a B+ and a W stud. I don't have a tachyometer so there is nothing to connect to the W. I have connected the B+ to the battery positive but it shows no voltage with the engine running.

 

The ad calls the alternator a "3 pin blade connector" alternator. I think that these connections must be for voltage sensing or for excitation, and without them the alternator can't start. I do notice there is another blade connector near the B+ stud (the stud in the bottom right of the photo).

 

Can anyone please help me identify what I need to connect these blades to?

 

 

 

[Tony Brooks]

Battery lead to the large insulated stud near the W one - its B+

 

Cable from warning lamp of the 6mm blade that is part of the group of two large and one small.

 

You could connect the battery cable to the two larger blades but the stud is more reliable.

[jetzi]

Thanks Tony!

 

2 minutes ago, Tony Brooks said:

Cable from warning lamp of the 6mm blade that is part of the group of two large and one small.

 

Currently I don't have a warning light. So I should attach a lamp positive to the 6mm blade in the group of 3 (the one on the right in the picture) and lamp negative to the battery negative. Will that then allow the alternator to produce current? I will try that, do I need to be concerned about the resistance of the lamp I choose or will any resistor do?

[Tracy D'arth]

Without the warning lamp connection to the 6.3mm spade on the triple connector block  the alternator has no excitation and will not charge. Use either of the large for the battery positive connection spade connectors in the triple or better the big stud at the bottom of the picture.

3 minutes ago, jetzi said:

Thanks Tony!

 

 

Currently I don't have a warning light. So I should attach a lamp positive to the 6mm blade in the group of 3 (the one on the right in the picture) and lamp negative to the battery negative. Will that then allow the alternator to produce current? I will try that, do I need to be concerned about the resistance of the lamp I choose or will any resistor do?

NO!  Warning lamp, at least 3w bulb, from ignition switch positive supply to bulb and other side of bulb to small spade terminal.  The small terminal needs a positive supply via a bulb, not an led, of sufficient wattage to excite the rotor in the alternator.

Edited February 7, 2021 by Tracy D'arth

[Tony Brooks]

5 minutes ago, jetzi said:

Thanks Tony!

 

 

Currently I don't have a warning light. So I should attach a lamp positive to the 6mm blade in the group of 3 (the one on the right in the picture) and lamp negative to the battery negative. Will that then allow the alternator to produce current? I will try that, do I need to be concerned about the resistance of the lamp I choose or will any resistor do?

 

As Tracy says: ignition  switch ON terminal >>>>>> one side of warning lamp (3 watt plus ideal but 1.5 watt will usually work), other side of the warning lamp >>>> that small blade you have correctly identified.

 

A warning lamp is easiest and will let you know when most alternator faults occur.

 

 

 

[nicknorman]

Just to give further explanation, most alternators you find on boats, require a switched warning light in order for them to work. The current flowing through the bulb goes via the rotor windings and is enough to provide some magnetic field to get the thing going. Once it is going, it generates its own supply for the rotor and the warning light goes out.

 

Other types of alternator, presumably the type you had originally, use a different system and the warning light is “optional”, just used to indicate failure and not used to kick start electrical generation.

 

So that is why your old alternator was quite happy without a warning light, but the new one isn’t.

[Eeyore]

As already said; D+ to one side of the bulb, and other side of bulb to a switched positive from the ignition switch. Main Positive from battery to the M6 B+ stud.

Edited February 7, 2021 by Eeyore

[jetzi]

Thanks for all the help and explanations. I understand the need for current to power the magnetic field now, thanks @nicknorman, I was a bit confused why it needed the bulb but it makes sense that the bulb shows that the current is powering the field, and once the alternator is generating power the light goes out.

 

I understand the need to connect the alternator field to the "ignition on".

 

I took my ignition apart and I've taken some pictures. I measured the voltage of each terminal against battery negative.

 

There are in fact two existing battery lights (presumably for my two alternators). The domestic battery light has two cables dangling in the engine bay near where the domestic alternator lives (marked in yellow and orange in the pictures). The battery warning light has a connection to a relay (shown in orange) and then directly on to the engine bay.  I'm not sure the purpose of the relay?

 

None of the warning bulbs currently do anything, but I've tested the battery warning light by directly connecting it to 12V and it does light up.

 

My ignition doesn't appear to have an "on" state. There are three positives, but two of them are permanently on and one powers the glow plugs.

 

So I'm not sure where to connect the other dangling wire (in pink), or if perhaps there is something wrong with my ignition.

 

[nicknorman]

It’s not entirely clear but it looks like the relay is a split charge relay, used to combine both engine and domestic batteries when the engine is running. The coil for these often wired across alternator D+ and 0v. So when the engine and ignition is off, there is no power to the relay coil. When the ignition is switched on, some of the current coming out of the warning light flows through the relay coil but not enough to operate it. Some of the current also flows into the D+ terminal to provide initial magnetism. Once the engine is running and alternator charging, the alternator raises the voltage on the B+ terminal which means that both ends of the warning light are now connected to positive - the light goes out. And also the relay now has 12v across it, so the contacts close and the alternator supplies charge to both sets of batteries.

 

Seems like at some point the alternator was replaced with a 6 diode model that didn’t need the warning light and couldn’t operate the relay. So presumably there is now some other means of charge splitting, like a manual 1-2-both battery switch?

 

Edit, no I see you mention having 2 alternators.

 

The other possibility for the relay is that it provided switched power for the domestic alternator warning light.

 

The general idea being that the ignition switch turns on engine battery power to go via the warning light and provide excitation for the engine alternator, and another connection on the same switch terminal operates a relay which connects domestic battery power to the domestic alternator warning light and on to provide excitation to the domestic alternator.

Edited February 7, 2021 by nicknorman

[jetzi]

7 minutes ago, nicknorman said:

It’s not entirely clear but it looks like the relay is a split charge relay, used to combine both engine and domestic batteries when the engine is running. The coil for these often wired across alternator D+ and 0v. So when the engine and ignition is off, there is no power to the relay coil. When the ignition is switched on, some of the current coming out of the warning light flows through the relay coil but not enough to operate it. Some of the current also flows into the D+ terminal to provide initial magnetism. Once the engine is running and alternator charging, the alternator raises the voltage on the B+ terminal which means that both ends of the warning light are now connected to positive - the light goes out. And also the relay now has 12v across it, so the contacts close and the alternator supplies charge to both sets of batteries.

I think the relay might be a red herring.

 

I'm going to disconnect all the wires from the ignition switch and see if I can figure out which terminal is which. Assuming it's in proper working order, I should be able to connect the other side of the battery warning light to the Aux.

 

I'm following @Tony Brooks's guide to ignition switches, I have a Type 3 so I should be able to determine which of the 5 terminals go where.

 

My hunch is that they aux and off have been connected together somewhere in the rats nest, meaning that there isn't any "ignition on" setting at the moment.

 

[nicknorman]

See my edit.

 

you might be right about the rats nest, but the other possibility is that the switch is a bit damp and leaky. When you are looking for voltages with a meter, one problem you can encounter is that since the meter takes virtually no current, a very high resistance connection (damp circuit board etc) allows the 12v though to the meter. If there was any load on the circuit, the voltage would in fact plummet to 0v

[Tony Brooks]

It looks to me as if the second alternator may be an after build addition. This makes it hard to form an opinion without a wiring diagram.

 

All ignition switch terminals should have 12V on them at some point in the switch sequence. There is no need for a negative to the ignition switch and that is what 0V suggest if you are measuring the voltage correctly. You can get 0V  in some positions of the battery feed has been connect4d to the wrong connection on the switch.

 

The 9V when on heat suggest a 3V volt drop to me so that won't help cold starting.  Maybe the switch is old and making a poor contact.

 

Take the feed to the new switch from the switch terminal with the red and the brown cable on it.

 

The relay is just being used as a junction box now, with the black wire not connected to battery negative (0V) it simply will not work. I think Nick is correct, it's an old split charge relay.

 

 

 

 

[jetzi]

My battery is getting low so I decided to "hack it" for now and just touch a wire to the positive to excite the alternator so that I can get it charging, which it now is. Success!
 

I removed all the wires from my ignition terminals and tested each position in turn.

 

Turns out that only 2 of the 4 positions work - start and glow. The one marked "50" (DIN72552 calls it "Starter control") I think is the "off" position which isn't needed for anything, but without an "Aux" position "on" I can't power the alternator excitation.

 

Is it worthwhile trying to take the switch apart to try to repair the Aux position? Otherwise I could just replace it with a toggle switch.

 

 

 

  

46 minutes ago, Tony Brooks said:

The 9V when on heat suggest a 3V volt drop to me so that won't help cold starting.  Maybe the switch is old and making a poor contact.

The glow definitely does do something, the engine won't start without it. But yes I'm sure the swich is as old as the boat so... 20 years old and probably not making a good contact.

 

I think you are both right about the relay. I have a separate split charge relay mounted near the battery so this one isn't needed. I think I might just remove it totally to try to simplify the rats nest.

Edited February 7, 2021 by jetzi

[nicknorman]

Yes the AC (accessory) terminal should be live with the ignition on. You could have a look inside, there will be some kind of board with metal (copper?) tracks on it, and  a wiper moving over it when you turn the key. Quite likely the copper tracks are burnt out or badly corroded. I suggest that any maintenance you do now should only be regarded as temporary, you willl need to get a new keyswitch soon!

These things are not really designed to be taken apart, but it is possible. There will be springs and balls that fall out, so don't lose them!

Edited February 7, 2021 by nicknorman

[Tony Brooks]

If you get it apart without damage  doubt you will rebuild it reliably. The terminal base is normally swaged into an alloy housing that tends to break.

 

Where did those numbers come from, are they on  the switch or are you guessing from the DIN charts.

 

Normally you don't use a split charge relay on a twin alternator system although some do to combine both alternator outputs while the batteries are low. I don't see why you need a split charge relay. A Relay close to the engine may be a glow plug relay fitted to hide that 3V volt drop.

 

 

[jetzi]

3 minutes ago, Tony Brooks said:

If you get it apart without damage  doubt you will rebuild it reliably. The terminal base is normally swaged into an alloy housing that tends to break.

 

Where did those numbers come from, are they on  the switch or are you guessing from the DIN charts.

 

Normally you don't use a split charge relay on a twin alternator system although some do to combine both alternator outputs while the batteries are low. I don't see why you need a split charge relay. A Relay close to the engine may be a glow plug relay fitted to hide that 3V volt drop.

 

Yeah doesn't look like I'll be able to take it apart easily and like Nick says the whole switch is probably on its last legs.

 

I think what I'll do is wire up the exciter to a toggle switch for now and look at replacing the ignition key switch at a later stage.

 

The numbers came from the switch and the labels from the DIN chart.

 

My other 40A (starter) alternator is completely defunct, I have a replacement for that too, though, when I get around to it. Currently both starter and domestics are charged from the domestic alternator that I've been playing with today. Who knows what the original configuration was, but I expect it was a completely separate starter and domestic system each with its own alternator.

 

I think this will do for now. Thanks for all your help.

 

 

[Tony Brooks]

Seems a good plan.

[Tracy D'arth]

9 minutes ago, jetzi said:

 

Yeah doesn't look like I'll be able to take it apart easily and like Nick says the whole switch is probably on its last legs.

 

I think what I'll do is wire up the exciter to a toggle switch for now and look at replacing the ignition key switch at a later stage.

 

The numbers came from the switch and the labels from the DIN chart.

 

My other 40A (starter) alternator is completely defunct, I have a replacement for that too, though, when I get around to it. Currently both starter and domestics are charged from the domestic alternator that I've been playing with today. Who knows what the original configuration was, but I expect it was a completely separate starter and domestic system each with its own alternator.

 

I think this will do for now. Thanks for all your help.

 

 

You have a terminal on the switch with no wire, what does that do when you switch on?

[Eeyore]

You might be able to use a switch and contact cleaner spray, if theres a gap to spray it into. I got lucky with mine for a similar fault.

Edited February 7, 2021 by Eeyore

[Tony Brooks]

I still think the main feed may be on the wrong terminal so it would be worth testing the switch as below.

 

Turn the key to the off position and look at the back to find a single large terminal and connect one wire from the multi-meter, set to buzzer, to it.  You won't have a large terminal so you need to find a terminal that shows no continuity with any other terminal. That is the main input terminal.

Mark the terminal to show it’s the battery feed in. You may have to test all the terminals in all permutations.

 

Turn the switch to the on position and with one lead on the feed terminal touch each other terminal in turn. When you find one where the meter buzzes mark it as Ignition on/auxiliary feed

 

Turn to the first sprung position and hold it there. Repeat touching terminals ignoring the aux one you have just identified. The one that buzzes mark as glow plug feed.

 

Turn to the second sprung position hold it there. Repeat touching terminals ignoring the aux and glow plug one you have just identified. The one that buzzes mark as start

 

 

 

[jetzi]

46 minutes ago, Tracy D'arth said:

You have a terminal on the switch with no wire, what does that do when you switch on?

 

Nothing at all.

It's marked "50" which according to the DIN72552 chart is "Starter Control". I'm not sure what that means, but I believe it relates to the "Off" position since the "Glow", "Aux" and "Start" terminals are accounted for.

It doesn't show any voltage at any key position (I tried all 4).

 

19 minutes ago, Tony Brooks said:

I still think the main feed may be on the wrong terminal so it would be worth testing the switch as below.

Thanks Tony, I performed this test which is how I produced the image below.

Glow (sprung anticlockwise) and start (sprung clockwise) turn on terminal 19 and 17 respectively.

 

But when the key is in the other two positions (Off and Run) all 4 other terminals are off.

 

1 hour ago, jetzi said:

 

I've wired up the exciter to a toggle switch and tested the process now. Turn on exciter - start engine - light goes off - turn off exciter. It isn't great but it will probably keep me going for awhile, particularly when you consider that it's 60 quid for a new ignition switch! (https://www.boatpartsandspares.co.uk/beta-marine-ignition-switch-528-p.asp) Otherwise I might get rid of the ignition altogether and just use push buttons.

 

 

[nicknorman]

If it’s any help, this is from the Beta43 manual. 30 is the connection to the battery, AC provides switched power to warning lights etc, 17 and 19 are heaters and starter (cant remember which way round). No connection to 50.

 

Edited February 7, 2021 by nicknorman

[Tracy D'arth]

6 minutes ago, jetzi said:

 

Nothing at all.

It's marked "50" which according to the DIN72552 chart is "Starter Control". I'm not sure what that means, but I believe it relates to the "Off" position since the "Glow", "Aux" and "Start" terminals are accounted for.

It doesn't show any voltage at any key position (I tried all 4).

 

Thanks Tony, I performed this test which is how I produced the image below.

Glow (sprung anticlockwise) and start (sprung clockwise) turn on terminal 19 and 17 respectively.

 

But when the key is in the other two positions (Off and Run) all 4 other terminals are off.

 

 

I've wired up the exciter to a toggle switch and tested the process now. Turn on exciter - start engine - light goes off - turn off exciter. It isn't great but it will probably keep me going for awhile, particularly when you consider that it's 60 quid for a new ignition switch! (https://www.boatpartsandspares.co.uk/beta-marine-ignition-switch-528-p.asp) Otherwise I might get rid of the ignition altogether and just use push buttons.

 

 

You can buy a diesel ignition switch from any motor  or tractor factors, ebay or wiring component suppliers, its a common part maybe with a plant key rather than what you have, They are about £6

[jonathanA]

And there is your first boatng lesson anything with 'marine' in its name add an extra 0 to the price.  Loads of generic ignition switches available for £6 - £15 quid as tracy says. But probably not with the same key you have (so what)

[jetzi]

2 hours ago, nicknorman said:

If it’s any help, this is from the Beta43 manual. 30 is the connection to the battery, AC provides switched power to warning lights etc, 17 and 19 are heaters and starter (cant remember which way round). No connection to 50.

 

Thanks, this matches what I determined exactly. 17 is the starter.

 

1 hour ago, jonathanA said:

Loads of generic ignition switches available for £6 - £15 quid as tracy says.

 

Good to know thanks! I am a bit surprised though as the switch has to handle reasonably high current, so I'm surprised a 6£ switch would be chunky enough to take it?