The Triumph Dolomite Club - Discussion Forum

Hi All,
Ever since I restored my 1300 fwd, the ignition light stays on when the car is started - a quick blip on the accelerator puts it out, car runs normally and charges.
The other day when I turned off the ignition after a run, the ignition light stayed on. If I turned 'on' the ignition the ignition light went out and the oil and handbrake light came on as normal. Thought no more about it until next day when the light was out, but battery totally flat! After charging, the car ran well and I assume charging as ignition light was off, lights were bright at night and all seemed ok until parking and switching ignition key off - then the ignition comes on.

I have checked on the web and some say that a newly fitted accessory could cause it, but I have not done any wiring for a long time. Some say its the ignition switch, some say its the alternator and some say a fault in the wiring or earth.

Has anyone had a similar problem as I do not think this is only related to fwd's, appreciate your thoughts?
Pete

Alternator diode pack is the first thought that comes to mind, assuming you have an alternator fitted

Sorry, should have mentioned this - it has an alternator.

Pete, I have a spare alternator here in Stourbridge if you want to swap them over to eliminate or prove it...

xvivalve wrote: Pete, I have a spare alternator here in Stourbridge if you want to swap them over to eliminate or prove it...

Pull the plug out of the alternator and when the light goes out it is the alternator.

Jeroen

I had this a while ago on a Dolly, it was the lead in the back of the alternator, i took it off cleaned it up and it never happened again.

Pull the plug out of the alternator and when the light goes out it is the alternator.

Well, yes, that as well.

I believe 1300 FWDs were originally fitted with a dynamo and a variant of the Lucas RB340 control box.
Now if the alternator conversion involved " looking like the original " the wiring would have been done by modifying the wiring to the control box ( Thick brown to "B" and brown / yellow to D / WL ).
This has the problem that if the voltage control contacts stick, then battery current is fed back in reverse through the Ignition warning light and through any leakage path back to earth as the bulb is a low current one.( The heater motor being on for instance).
Go for the simple test first as has been suggested of pulling the alternator plug.

If the light is still on then come back to us and we can suggests suitable wiring mods.
( But disconnect the battery when not in use as it will be discharging .)

Of course, if the car was never equipped with a dynamo .... please delete this.
HTH,
Tony.

Thank you all for your comments and also to xvivalve for offer of try-out alternator.
I pinched the alternator off my MGB and light went out straight away, so all is well.................
We went out for a ride today and noticed that the ignition light was very faintly coming on and off. Nice day today so in the bright daylight, you cannot see it, but when in shade you can just about see the light coming on and off.
So either this alternator is also on its way out (it has not been used for about a year) or wiring problems.
The car wiring with alternator is as I bought the car, with no control box.
The wiring has a large connector block with thick brown wire from battery on one end connecting to thick brown and yellow.
Another connector has thick brown wire from battery on one end connecting to thick brown and white, also thinner brown and white wire.
There are two other thinner wires connected together - brown to brown and yellow.
Any thoughts please?
Many Thanks
Pete

Something doesn't sound quite right there, but I can't put my finger on what.
The 2 linked thin wire are for the warning light.
When I've converted in the past, I have then linked the 3 thick brown wires together, that's 2 going into the car, and one coming from the dynamo, now the alternator.

If those 2 are going to the battery, unless I've misread,where's the alternator feed gone?

epcot_pete wrote: ↑Tue Sep 26, 2017 5:27 pm
The car wiring with alternator is as I bought the car, with no control box.
The wiring has a large connector block with thick brown wire from battery on one end connecting to thick brown and yellow.
Another connector has thick brown wire from battery on one end connecting to thick brown and white, also thinner brown and white wire.
There are two other thinner wires connected together - brown to brown and yellow.
Any thoughts please?
Many Thanks
Pete

Hi Pete,
Good choice the MGB alternator assuming it is the 3-terminal one like mine.
Couple of questions first just so we know where we are.

* Has the original problem of the IGN light being on with the Ignition key OFF now gone away ?
* Do you have an Ammeter on the dashboard and is it still doing anything ?

As to the wiring, yes we are looking at a car converted from dynamo to alternator.

epcot_pete wrote: ↑Tue Sep 26, 2017 5:27 pm
The wiring has a large connector block with thick brown wire from battery on one end connecting to thick brown and yellow.

This looks O.K. ...

epcot_pete wrote: ↑Tue Sep 26, 2017 5:27 pm
There are two other thinner wires connected together - brown to brown and yellow.

Now provided the brown /yellow wire goes to the bottom terminal on the alternator ( and nowhere else ) as Bruce also notes this is also O.K.

epcot_pete wrote: ↑Tue Sep 26, 2017 5:27 pm
Another connector has thick brown wire from battery on one end connecting to thick brown and white, also thinner brown and white wire.

Now this is where I reckon it is falling over.

* What colour wire(s) go to the top large terminal on the alternator please ?

* What colour wires go to the middle alternator terminal please ?

The brown / white wires typically go to an ammeter.
These unfortunatly drop volts depending where they are wired so the regulated output voltage from the alternator is not the same as the battery charging voltage. ( So the IGN light lights dimly )

Hence the question of whether the ammeter is still installed and still works.
I think we would need to know exactly how this is wired to check.
And this is one reason the manufacturers changed to battery condition meters ( voltmeters when alternators replaced alternators.
HTH,
Tony.

Hi Pete,

I converted my 1300fwd from Dynamo to Alternator way way back. I removed the ammeter during the conversion, but the wiring should be as below.

You should have a thin brown and yellow wire from the alternator connected to a thin brown and green wire this is the charge light circuit.

You should then have a thick brown and yellow wire from the alternator to the starter solenoid - and from there to the battery through the positive lead.

There should then be the two thick brown wires originally from the voltage regulator connected together.

If it was all working well until recently then it probably is just the alternator diode - rule that out fully before going any further. Remember that the MG one could also be on it's way out - I had a 1500 Midget with a similar faintly glowing light that only went out at high revs I swapped the alternator for one of the "spares" I'd kept that had the same fault - a new one solved the problem.

Good luck Graham

Sorry for delayed reply and thanks to all that responded.
I have done what I should have done in the first place and looked at the wiring in more detail and done some tracing of where they come from and go to. I have used Haynes manual wiring diagram for help.
I have attached a picture of the connector to help with my explanation and what I have is:

Thick brown from battery (I suppose it could be from starter solenoid?) to one side of the connector and has a black loop wire to the other side of the connector, effectively making both sides 'live'.
Connected to this connector are:
Thick brown/white (think it is master light switch and went to 'B' on control box)
Thick brown/yellow (definitely goes to alternator and fitted to 'D' on control box)
Thin brown/white (think it goes to ammeter and fitted to 'B' on control box)
There are two other wires joined together with blue connector - Thin brown/yellow from ignition light and thin brown/green from alternator.

The ammeter is still connected and slightly flicks to negative side when ignition is switched on, otherwise does not move. Should I disconnect this?
There are two wires to the back of the alternator which has three male spade connectors. Thick brown/yellow to outer male connector. Thin brown/green to other smaller outer male connector. There is no wire to middle male connector.

I hope this is clearer for you to advise me on what to do.
Looking at it now, the wiring looks awful so I need to tidy it up anyway!
Appreciate your time
Pete

Hi Pete, Thanks for the update.

Can you do an extra test please.
* With the engine running and warmed up you mentioned you can see the IGN light glowing occassionally.
If you give the engine about 2,000 rpm, them turn on headlights + heater blower + heated rear window + wipers does the IGN light glow much brighter ? ) Just to give an idea of the problem.

* Do you have a voltmeter ? If so can you check the voltage across the battery in this state and also the voltage on the thick brown yellow wire at the alternator please ?

From your description the thin brown yellow and brown green being linked and going to the small connector on the alternator is O.K. This is the IGN light connection, provided it goes nowhere else.

I'd try and leave the ammeter in for now just for originality.

The thick brown/yellow wire going to the top large terminal on the alternator is also O.K. , but as you say a tidy-up of the wiring may help , perhaps using the large style 8mm? yellow spade crimp connectors. These have a much higher current rating.

* One thing that you may need is an additional thick brown wire from that middle connector on the alternator to also connect to your thick brown wire at the starter solenoid.

The reason is that on some alternators that is used as a remote sense wire that controls the output voltage.

The next bit is a technical explanation which you can skip if needed.

Start of speech !
There are at least 3 different variants of MGB alternator. But all do the same basic function.
Since you have an MGB you are bound to have the Haynes manual.
Pages 190 to 201 show the evolution of the charging system.
Fig 10.26 shows the positive earth dynamo with the IGN light fed from the control box.
Fig 10.27 shows the early alternator (15ACR) with the separate electronic control box.( not your one).
Fig 10.28 shows the later version with no external control box but with the electronics now inside the alternator casing.
The IGN light wire also feeds a 2nd terminal to provide alternator field excitation, but the function is the same.
There are 2 brown wires. One thick on that carries the main current and a thin one that is the sense wire . This looks at the voltage on the end of the brown wire and feeds the voltage back to the alternator and adjusts the output voltage to be within range. Note that on this model if this brown sense wire is disconnected the alternator voltage will go very high. Again with only 3 terminals this is not yours.
10.29 shows the 71/72 model with no sense wire. This is known as a Local Sensed model, but is not as good as a remote sensed unit.
10.30 shows the 73/74 model and the sense wire is back in.
This is probably the one you have fitted. If that middle large terminal is not connected there is a built in safety resister in the electronics to stop the output voltage going too high. Much better to have it properly connected to the starter solenoid brown wire in your case.
10.33 shows the next major change where the output current capability is going up and up ... and here, instead of a remote voltage sense, the 2nd large terminal is used in parallel with the 1st terminal to supply the high current, so there are 2 thick wires up to the battery. Voltage sensing is then local as per early models.
So Lucas have tried to maintain an element of backwards compatibility.
Which is good.

End of speech.

So all you have to do to ensure compatibility is have 2 thick brown wires each going separately to the battery connection at the starter solenoid and the IGN warning light going to the small spade connector.

Let us know how you get on.
I'm sure we can fix this.
Tony.

Thank you Tony, that must have taken some time to type, it is very much appreciated.
Will do all those things and report back.
Take care
Pete