Alternator warning light

[Roger]

Hi All,

I have some problems fitting an alternator on my Vitesse. I know there is a lot of information (too much!) about alternator conversions on this and other forums (and Youtube) but I just don’t get it… John added a link to a (MG) document about this subject here on this forum, but that document is 149 pages!! And that document focus mainly on replacing a Lucas Dynamo with a Lucas Alternator. I have sourced a cheapo 60A alternator which seems to be a copy of a Toyota or Nippon alternator. Then I found another very useful instruction on sideways here

In that thread Dave the author writes:

“Gain access to the back of the speedo, find the ignition warning light unit/holder which push fits into the speedo. You will need to discard this as the modern alternator system doesn't work in the same way. Buy one these lamp units CWL12 (link does not work anymore)”

My question is: Do I really have to buy a new warning light to make this alternator conversion work? If so why? (“doesn’t work in the same way….?”)

I guess we all like to do things we are good at, and I loath everything related to electricity. Consequently I’m daft regarding all things that has wires. I would be happy to spend some time drilling out a rusty snapped bolt instead. But I will not hear that sweet sound of a six cylinder Triumph unless it gets electricity, so I just try to keep calm and carry on connecting wires (randomly…).

Pictures of the alternator I got plus the wiring chart that came with it

Nice colours on the cables by the way, same as the Aaland Island flag 🙂

[Colin Lindsay]

When converting to alternator I just connect the wires as per the recommended instructions; the ignition warning light always worked the same way provided you connect the thin green yellow and green brown wires together - the link explains:

http://www.tssc-devon.org.uk/technical/13-alternator-conversion.html

[Clive]

I have denso 40A versions of that alternator

I left the S connection unattached. 

Warning Light I used the std Triumph lmp in the speedo. Connected to the L terminal

And the IG is indeed an ignition controlled live. 

Both my Spitfire and Toledo have been faultless. Warning lamp works correctly.

 

Brise motorsport suggest that the wiring diagram you have is correct though.

https://brise.co.uk/product/denso-60a-motorsport-alternator-5021-60/?v=79cba1185463

 

So I would suggest following the manufacturers instructions. 

And that means the sideways post may well make sense, as that bulb will be insulated from the speed (and therfore not earthed) 

(If that is the case, it is odd that mine are OK!)

 

[Roger]

Thanks Clive and Colin, then I will try using the original warning light!

[PeteH]

I`ve swapped a couple over the years, a Vitesse for one. Always used the existing light the bulb does not differentiate between live and earth so long as it has a circuit?. Might only be an issue if you had LED`s in the lamp holder?

Pete

[Roger]

15 minutes ago, PeteH said:

Might only be an issue if you had LED`s in the lamp holder?

Thanks Pete, no LED in there.

[NonMember]

2 hours ago, clive said:

And that means the sideways post may well make sense, as that bulb will be insulated from the speed (and therfore not earthed) 

I don't think the sideways instruction makes sense for that alternator - it seems to want the warning light wired exactly as Triumph did. It's not earthed even on dynamo cars.

[Clive]

8 minutes ago, NonMember said:

I don't think the sideways instruction makes sense for that alternator - it seems to want the warning light wired exactly as Triumph did. It's not earthed even on dynamo cars.

Hang on, is the alternator WL not earthed via the speedo?? Actually, makes sense, but all the other lamps are earthed.

So I got it wrong in my post, but right when I converted mine? 

I am now questioning my sanity. Seems to be happening more often these days.

 

[68vitesse]

Always thought warning lamp was earthed through the alternator or dynamo, live frome an ignition switched circuit. When the alternator or dynamo starts charging the warning light has two lives and therefore goes out.

Could be wrong, often am and not an auto electrician.

Regards

Paul.

 

 

 

[Clive]

9 hours ago, 68vitesse said:

Always thought warning lamp was earthed through the alternator or dynamo, live frome an ignition switched circuit. When the alternator or dynamo starts charging the warning light has two lives and therefore goes out.

Could be wrong, often am and not an auto electrician.

Regards

Paul.

 

 

 

You are absolutely correct. One sde of the warning light is connected to a white (ignition circuit) wire, the other off to the alternator.

So the sideways post is a complete red herring. And my alternators are wired correctly.

 

[Roger]

Thanks for all your help! There is indeed a tremendous amount of information about this on the internet, but also a tremendous amount of wiring solutions depending on the type of alternator connection (2,3 or 4 connections) car model etc. The post on Sideways does not seem to be 100% correct.

Still confused, but now on a higher level!

[Pete Lewis]

going back a good few years with intro of alternators on some fairly slow perkins we uprated the warning bulb to a good few watts to bring the cut in voltage down to match the low idle and not so high max revs of around 2200 dont remember if it was 5 /10/21 watts but back then it worked 

Pete

 

[PeteH]

Had to really think about that. Its a LOT of years since I did DC theory. So one assumes the circuit is fed (initially) from the Ignition switch live?. To have a complete circuit it must return via the Alternator live? to show as a light on the Speedo?. However when the alternator output rises the lamp is then only in the Live wire and the light extinguishes, no return circuit?.

Pete

[Roger]

On 04/02/2022 at 19:25, clive said:

I left the S connection unattached

As I mentioned above, I'm completely ignorant regarding all things electricity. But I found this (Toyota) wiring diagram that looked almost identical with the diagram that came with my alternator. It seems like the S connection has some magical function depending on where you attach it. My thinking was to attach it as close as possible to the battery +.   Never trust anything I write about wiring and electrical stuff, I have no idea what I'm talking about.

[NonMember]

14 hours ago, Roger said:

It seems like the S connection has some magical function depending on where you attach it.

Not really magic. It's a "sense" wire, intended for "battery sensed" configuration rather than the more common (simpler!) "machine sensed". It allows the alternator's regulator to compensate for the resistance (and hence voltage drop) of the wire between alternator and battery.

[Pete Lewis]

many used a sensing wire  was common on vauxhall vivas of the day  with a delco alternator had a lucar blade halfway down the case  

never seen on a Lucas unit 

thought that idea  had al but disappeared with more modern control systems ..........  obviously not 

Pete

[Roger]

3 hours ago, NonMember said:

It allows the alternator's regulator to compensate for the resistance (and hence voltage drop) of the wire between alternator and battery.

Thanks for explaining NM, that makes sense.

[Roger]

Update: The alternator does not work when in the car, following advice above. The strange thing is that the alternator DID work when I had it in a vise, connected to a battery on my bench (made it rotate with my drilling machine and an old fan belt). Connections as per the diagram attached in the box and using an old light bulb I found. The lamp I used was originally from breaks or maybe flasher lights. I don’t know how many watts (behind tape now) but probably a lot more watts in that bulb compared to the lamp on my dashboard. Which makes me think about what Dave wrote on Sideways that the type of light bulb might have an impact on the system after all (certain amount of resistance needed???). OR something else is wrong in my wiring. The usual disclaimer: Consider everything I write in the “Electrical section” of this forum to be complete bollocks. Will try to connect everything again this evening

[Peter Truman]

I seem to remember the bulb wattage affects the alternator cut in revs ie recharge rate hence LED’s we’re no good as alt wouldn’t cut in till say 4000 revs.

maybe suffering from old age here!

[Pete Lewis]

no ive said before on some slow perky units we added a big bulb to bring the cut in revs down cant remember if we used 10w or 21w

as you could never get the light out 

all down to old diesels maxing at  2200  and 400 idles with small crank pulley  this was back in the 60s  early alternators etc.

so youre not dreaming Pete

 

Pete

[Iain T]

Roger, after two new lucas type alternators failed I fitted a Brise. Fit and forget! Like you I'm not electric savvy, what I did on my Vitesse was tuck away the Brown/Green cable (not necessary on the Brise) and connected the Brown/Yellow to I believe the L terminal (someone please say if its the S!) I then ran a new cable (that's the green on the photo) from the alternator IGN to a switched ignition white on my fuse box. Connect the large charge cable alternator to battery and hey ho it works! The ignition light functions and it charges! 

I'm not sure if the green cable is the correct size and my terminals are not insulated, apart from some tape, but it's been fine for the last two years and 1000 miles. 

I hope this helps one electrical novice to another. 

Iain 

 

[Roger]

20 minutes ago, Iain T said:

I hope this helps one electrical novice to another

Thanks Ian, I certainly need all the help I can get! Pictures are always appreciated. I assume you have left the control box for the dynamo "as is" without any modifications? In the future I would like to eliminate that thing completely and replace it with a fuse box. But at the moment I just need a working alternator so that I can start the engine and tune the carbs weather permitting. Any bodge that makes the alternator work will do for now. I live close to the harbour here and I have been tempted to go down there are just throw the alternator in the Baltic sea. I always find some very important mechanical problem that needs my immediate attention as soon as I have failed to solve an electrical problem.

[Clive]

2 minutes ago, Roger said:

 I assume you have left the control box for the dynamo "as is" without any modifications? In the future I would like to eliminate that thing completely and replace it with a fuse box.

There is a guide to converting somewhere.

From memory, 

(1) you no longer need teh black earth wire

(2) the F and WL wires need joing (Field, Warning Light)

(3) all the browns (I think they are all just plain brown) get joined together. This is where you can use fuses at a later date if you wish. 

On one car, I used copper pipe, slit and made into a flat sheet. Then cut it to accept all the spades. Sid the same for the F and WL. Wrapped in tape and put in a small plastic electronics box.  Nest car I took teh insides out of a control box (I had a few) and soldered heavy copper wire to join the various connectors. Looked nice and standard, until you saw the alternator.

[NonMember]

5 hours ago, Roger said:

The strange thing is that the alternator DID work when I had it in a vise

Well, if it worked like that but doesn't now then there's something different. So what is it?

The bulb rating shouldn't be the problem. It used to make a difference on old alternators with their very crude control system, but it shouldn't matter on a new / smart alternator. Usually a dumb one doesn't need the separate ignition connection so yours is probably not bulb sensitive. However, it's an easy test (no need to wire it in neatly, just connect up the one you used on the bench) so worth doing.

So that leaves the rest of the wiring. As Clive says, if you are converting from a dynamo you need to isolate the control box. Double check all your wires. With the ignition off, check for 12V at the big lug and the S terminal. Turn ignition on and check you also get 12V at the IG terminal. Use the alternator casing as your earth point - you need to be sure that's properly earthed to the engine and thence to battery -ve.

[Iain T]

8 minutes ago, Roger said:

. I assume you have left the control box for the dynamo "as is"

The PO converted to an alternator so I only have a (actually two) fuse boxes no control box. It made my life easier! 

As I said beware of Lucas alternators. The WOSP alternator fitted by the PO failed. My first Lucas type again just stopped charging, the the second had such a vibration it shook the engine, exhaust, chassis and me! All in the bin but the Brise has been faultless. I just know I shouldn't have said that! 

Others, I notice Clive has posted, can advise on dumping the control box. 

Good luck, it must be a bit nippy in Aland? 

Iain