6B IGNITION WARNING LIGHT

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franky
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6B IGNITION WARNING LIGHT

Post by franky » Mon Nov 12, 2018 12:16 pm

Hi guys
I’m having an issue with the ignition warning light on 1980 GTE 6b. It remains on even when charging. The ammeter shows good charge and is working correctly.
I have looked on the existing forums but can’t find anything.
I removed the block from the alternator and cleaned the terminals and found that now the light does dim slightly when engine is running at above tickover but still remains on.
One point of interest was I tried connecting the terminals to the alternator without the block and found the light came on without the ignition being switched on, then it went out when I started the engine. Weird maybe it’s a ghost!!!!
All the gauges are working but I’m not sure about the brake fail and brake pads warning lights which seem to be on the same circuit as the ignition warning light.
May I express my appreciation to Peter Freeman and his wonderful colour wiring diagrams which are so much easier to read than that in the workshop manual, as I am a complete novice when it comes to auto electrics.
Any guidance would be appreciated.



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philhoward
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6B IGNITION WARNING LIGHT

Post by philhoward » Mon Nov 12, 2018 12:22 pm

franky wrote:
Mon Nov 12, 2018 12:16 pm
ONE POINT OF INTEREST WAS I TRIED CONNECTING THE TERMINALS TO THE ALTERNATOR WITHOUT THE BLOCK AND FOUND THE LIGHT CAME ON WITHOUT THE IGNITION BEING SWITCHED ON, THEN IT WENT OUT WHEN I STARTED THE ENGINE.
That suggests the block is worn and not allowing correct connection of the terminals into the back of the alternator. I'm guessing (as I've never had a 6b) that it uses the "standard" Lucas-type alternator plug? If so, new ones (with new terminals) are available for a few quid. First one I found on ebay, for example: https://www.ebay.co.uk/itm/A127-ACR-ALT ... :rk:2:pf:0


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Roger Pennington
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6B IGNITION WARNING LIGHT

Post by Roger Pennington » Mon Nov 12, 2018 1:06 pm

Is it also possible that it might point to a fault in the ignition switch? (if the light is on without the ignition on?)


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6B IGNITION WARNING LIGHT

Post by demonbluedays » Mon Nov 12, 2018 1:19 pm

Or....as my se6 was similar...is the alternator starting to go maybe? It did it on the new one until Terry swapped from the smaller top terminals to the chunkier lower ones...But that's an upgrades 75a one


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6B IGNITION WARNING LIGHT

Post by Dennis Nicholas » Thu Nov 15, 2018 10:15 pm

The warning light wiring is as follows:-
Battery positive thick wire to starter solenoid terminal; that same terminal to ignition switch; ign switch to warning light; warning light to "ind' terminal on alternator; "ind" terminal inside to common of three diodes joined together also to field coil through which the circuit is completed to earth; the other side of each diode goes individually to one of the 3 coil windings all inside the alternator.
When engine not running and ign switch off there is no 12V on the light. Switch ign on and the 12V from the battery - via solenoid terminal appears on the warning lamp and then the "ind" terminal and via the internals of the alternator to earth so that the lamp is on. With the engine running and the 3 coils producing 12V out, that 12V appears at the "ind" terminal via the 3 diodes so 12V out cancels 12V in and no voltage across the lamp so lamp goes out.
To check:- 1. engine not running - disconnect Ind lamp at "ind" terminal of alternator (either on the plug or its own separate terminal depending on alternator fitted) connect + of meter to that terminal on the wire and negative to earth to measure Voltage; switch on ignition and meter should indicate 12V.....touch the terminal to earth and lamp should light. If it lights reliably with turning ign on and off several times then all is ok up to the alternator "ind" wire terminal and the problem is in the alternator or the wire connector plug/socket on the alternator. If not then the problem is in the wiring from the ign switch to the warning lamp or the connection inside the ign switch ........it is well worth opening the ign switch and cleaning its terminals anyway.....this is covered with photos elsewhere in the forum.
You say the indicator lamp comes on ok but does not go off when engine running but a good charge is showing on the car ammeter.......the 12V generated by the alternator for battery charging goes out of the alternator via a separate circuit and terminal to the 12V for the ign light. Thus your fault indication as described points to a poor terminal on the warning lamp "ign" wire or the internal wiring from ind terminal to diodes or diodes to the 3 coils. (could easily be a "dry" solder joint). (a dry joint is where the wire looks as if it is connected to whatever but the solder has not actually melted properly onto either side of the connection so the two bits are sometimes just touching and sometimes not)
2. With engine running and "ind" wire terminal disconnected you should put + of meter on alternator "ind" terminal and negative to earth and you should get 12V if internals of alternator are ok... if not then it is most likely the problem is with the diodes or the connections to them or the field coil.

To summarise it is necessary to realise that after the 3 coils that produce the 12V there are 2 paths in the alternator; one is via 6 diodes to the battery charging terminal and the other is via the 3 diodes to the "ind" terminal.

Dennis


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1980 GTC Trafalgar Blue, 2010 basic Skoda Yeti (petrol), Austin 7s, Rileys.

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