Ignition light comes on when there is no key in the switch

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Charles Farran
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Re: Ignition light comes on when there is no key in the switch

Post by Charles Farran »

Hi Vic,
Further to my last post i have checked the number stamped on the end of the coil & it is 16C6 which is the ballasted coil.
This was on the car which i have owned from new. It confirms the error in the BL ROM !
Cheers,
Charles
1980 Roadster
Ian Fozzard
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Re: Ignition light comes on when there is no key in the switch

Post by Ian Fozzard »

I've been following this debate with interest and some bewilderment🤔🤔!!
I 'm just pleased I have one of the simpler Bs (1972), I find the electrics on that challenging enough!!!

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Charles Farran
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Re: Ignition light comes on when there is no key in the switch

Post by Charles Farran »

Partial Extract from Late UK MGB Wring Diagram.jpg
I thought it might be useful to post up an extract from the diagrams freely available from auto wire on the internet so credit to them for this. (The attached is their copy of the Haynes version which is in colour that assists identification. (The relays here are shown as square , whereas the original last versions used on the RB cars were round)! If you click on the diagram it will increase in size)).
This set of wiring is how the cars with ballasted coils were set up.
I have included the fuse box plus the additional 3 in line fuses that were referred to in an earlier post.
The diagrams produced as a set by auto wire are much easier to read than the ones contained in the workshop / ROMs !
Cheers,
Charles
1980 Roadster
Vic Butler
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Re: Ignition light comes on when there is no key in the switch

Post by Vic Butler »

Charles Farran wrote: Wed Jul 07, 2021 9:40 am Hi Vic,
Further to my last post i have checked the number stamped on the end of the coil & it is 16C6 which is the ballasted coil.
This was on the car which i have owned from new. It confirms the error in the BL ROM !
Cheers,
Charles
Thanks Charles.. I have a Repair Operations Manual for 1978 B 's and a workshop manual for all B versions and both state the HA12 coil is fitted to all UK spec rubber bumper B's. I suspect my Lumenition coil has the same resistance as yours.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Vic Butler
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Re: Ignition light comes on when there is no key in the switch

Post by Vic Butler »

Ian Fozzard wrote: Wed Jul 07, 2021 10:03 am I've been following this debate with interest and some bewilderment🤔🤔!!
I 'm just pleased I have one of the simpler Bs (1972), I find the electrics on that challenging enough!!!

Ian F
I' m bewildered too Ian. Poring over wiring diagrams with a magnifying glass tracing wires requires a lot of concentration especially where the wire in question goes into a junction box and several wires of the same colour emerge and go to different items.
I don't like giving up so I'll keep on plugging at it. I think we're getting somewhere.
I'm self taught with vehicle electrics. Nobody bothered to teach.me (they probably didn't know) so each vehicle I've owned I've made a point of familiarising myself with the electrics.. It's not as difficult as most people think.
My first time with vehicle electrics was converting my 1952 BSA Bantam from direct to battery lighting by fitting a rectifier and battery with associated wiring. It wasn't difficult and was a vast improvement.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Ian Fozzard
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Re: Ignition light comes on when there is no key in the switch

Post by Ian Fozzard »

Well Vic, the confusion starts at a very fundamental level- those electrons are supposedly negatively charged I think? And yet they seem to emerge from the positive terminals of wherever they are found🤔! Never quite sure which way round the circuits they are going, let alone all of the other things to get your head around😁😁.

Ian F
1972 BGT, Blaze, Navy trim, recessed grill
1961 Midget, 948cc, Clipper Blue, Blue trim and weather gear
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Michael Barclay
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Re: Ignition light comes on when there is no key in the switch

Post by Michael Barclay »

There is also a link on the MGB REGISTER web page to electical diagrams.
Tech tips - Electrical tips then scroll down to the bottom of the page and click on electrical diagrams. The diagrams are in colour so do help tracing where the wires go.
i think if i owned a RB car , given all the postings on ignition and relay related problems i would do away with ballast resistor and fit a 12 coil. i have a chrome bumper car and have never had any issues with starting so not sure if this extra complcation is really required. Just my my opinion. :D
Mike Barclay
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Charles Farran
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Re: Ignition light comes on when there is no key in the switch

Post by Charles Farran »

Hi Mike,

I've never had a problem with my ballasted system! The problem seems to arise when cars have changed hands (inevitable given their age & a PO has hacked around the wiring/loom or it has been partially burnt out - see also last sentence).
My post of 9.43 am of the 7 July , which some may have missed, clearly shows the wiring for the ballasted system. (I copied a portion of the full diagram freely available form auto wire to really focus on the area relating to the ballasted system area). A relatively simple check of the various wire leads in connected or disconnected states with either a test bulb or Voltmeter / continuity tester with the ignition switch on or off etc. etc. should identify where there is a problem. Indeed , if the ballast resister wire/ resister is broken somewhere, it would be relatively easy just to insulate off each end and fit a replacement one. (Saves having to buy a new 12v coil that would be necessary if it was intended to run the car all the time with an non ballasted system)! More than once the problem has been caused by the incorrect starter motor with integral solenoid (i.e. without the additional IGN tag that sends full voltage under cranking) being fitted as a replacement for a RB car.

Cheers,
Charles
1980 Roadster
Not_Anumber
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Re: Ignition light comes on when there is no key in the switch

Post by Not_Anumber »

If Beech has difficulty starting the car as removing the wire from the starter will have lost the ability to bypass the ballast resistor could he work around this by installing a wire from the C2 terminal of the Starter relay (it will have one large White/ Red wire) to the + side of the coil ?
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Charles Farran
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Re: Ignition light comes on when there is no key in the switch

Post by Charles Farran »

Hi Chris,
I think this approach was considered a little while ago & the problem is that once the engine was running you would have a current flowing back from the coil + side which would be fed by the ballasted wire which then would be "live" as the ignition would be in the "on" position rather than crank position.Therefore a current , albeit at a lower voltage would be sent to the starter motor/solenoid which is not required when the engine is running !
(This might damage the solenoid never mind cause problems elsewhere).
I think it was Mike who came up with the solution of a different relay to replace the starter relay, which had an additional terminal that would effectively replace the function supplied by the last type of starter motor with the solenoid that had the additional IGN tag.
Cheers,
Charles
1980 Roadster
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