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 Beech,

One more thing to check.
I'm not sure that when you had the various issues arising whether the separate in line fuses just outside the fuse box were disconnected & put back together in the same arrangement. On my 1980 car (& it should be the same for your 1978 model) there are 3.
One connects N to N (Brown to Brown) which is the permanent feed for the Hazard Warning Flasher which needs power when a car breaks down.
One connects WN to G (White/Brown to Green) which protects the electric fan circuit & is therefore only live when the ignition is switched on.
One connects WN to G ( shown as white in the Haynes diag i have previously referred to ) which is dog tied from the white wire that goes to the ignition relay. (This has an identification band) - this fuse is for the HRW of an MGBGT - they used the same loom for the roadster as well as the GT so is not utilised in a roadster.
If the first one was incorrectly connected to the second one above that might also create a similar issue to what you have with things still being live, without the ignition being on until you "broke the link" by disconnecting one of the wires that goes to the + side of the coil.

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 »

The fuse holder where the green wire is at the front connects the radiator fan supply via the Otter switch to the fusebox. Green to the switch and fan, white/brown to the fuse holder.
The other one the white/brown wire comes in at the front. This wire goes to the ignition coil via the resistive wire. The green wire goes into the loom and is joined at a block where it splits and goes to the heated rear window and its switch.
My October 1977 built car has a 3rd in line fuse with a brown wire in and out which is for the hazard warning lights.
As Charles says, make sure that the fuse holder where the white/brown wire goes in the front has a green wire at the other end and vice versa for the other one.
This seems a very odd set up and the temptation to change the holders so the same colour wires go in both ends can be difficult not to resist.
The later rubber bumper cars have a wiring set up that defies logic.
The holders are numbers 44 & 44A in the BL wiring diagram.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Not_Anumber
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Re: Ignition light comes on when there is no key in the switch

Post by Not_Anumber »

Is Beech likely to suffer any starting difficulties now having removed the wire from the starter to the + side of the coil ? It wont now be getting the full voltage boost intended when starting, just the same reduced voltage via the ballast resistor it would get during normal running.
Vic Butler
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Re: Ignition light comes on when there is no key in the switch

Post by Vic Butler »

I suppose time will tell, assuming the coil is still 6v. It's an unusual problem to which I don't have a logical answer. In theory with the direct feed from the starter motor disconnected at the coil it shouldn't start at all. Mind you, we are assuming that's the wire that's disconnected as there's no way of telling. I reckon the wiring has been messed around with. Perhaps another starter motor without the direct feed terminal has been fitted at some time and the wiring altered.
The only way would be to check the starter motor solenoid connections but getting the rubber cover off is a pig of a job.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
Not_Anumber
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Re: Ignition light comes on when there is no key in the switch

Post by Not_Anumber »

As this is a fault which has just occurred out of the blue I wonder if something thrown up from the surface of the road could have knocked the wires at the back of the starter motor and forced the wires/ terminals together thus making the wire to the coil permanently live. It would then probably be held in (the wrong) place by the tension of the rubber boot until someone reached down and moved it if or the car went over a large bump.
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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 »

A picture under the bonnet of the wiriing to the fuse box might help as well to make sure the wires each side of the bottom two are attached to the correct terminals. The bottom should have the Browns on the supply side with the pinks on the outside. The next one up should have the whites on the supply side with all the greens on the outside.
Clearly the wiring and/or the starter motor has possibly been modified from original spec.If the original ballasted coil has not been changed to an unbalasted coil & full voltage is supplied when the engine is running rather than just being cranked then the coil will in due course be burned out.
The two WG leads need testing to see which are live with the ignition off, ignition on & also when cranking & what the voltage is.This would help establish what is not operating as it was originally intended to do.
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 »

Not Anumber, are you able to remove the cover from the starter motor to see what wires go where on the solenoid? I know it's an awkward job but it could possibly throw a light on this intriguing mystery you've presented to us.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
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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 »

Vic,
The issue has been raised by Beech, not "Noa anumber".
That said it would help to resolve thd issue.
The easiest way to remove the cover, assuming it is still in place covering the starter , is to jack the car up, put safely on axle stands & pull the cover towards the front of the car & pull it down.(Assuming a garage lift is not availabke). It may help to warm it up with something like a wall paper stripper or a hair dryer to soften up the plastic / rubber as it becomes very stiff. (It will be filthy)!
Cheers,
Chrarles
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 »

Sorry Beech, my brain is becoming addled with poring over wiring diagrams with a magnifying glass tracing wires. Thanks for the correction Charles.
Charles, as far as you know does your MG still have the original coil? I was wondering if there is anything written on it to identify the type. Mine doesn't as it now has a Lumenition ballast resistor coil.
The workshop manual shows the coil.as a Lucas HA 12 with a resistance of between 3.1 & 3.5 ohms. This to me appears to be a 12v coil.
In the US/ Canadian spec cars the coil is a Lucas 16C6 with a resistance of 1.43 to 1.58 ohms with a ballast resistor resistance of 1.3 to 1.4 ohms. No mention of a ballast resistor is mentioned in the engine tuning data for UK cars.
Beech, have you a multimeter to measure the resistance of the coil on your car? Charles, could you measure the resistance of your coil too if it's still the standard one? Because of my recent hip replacement I can't bend or twist so working on my vehicles is not allowed so I can't measure the resistance of the Lumenition coil at present.
1977 Stage 2 MGB GT
1975 SWB Series 3 Land Rover with a later 2.5 petrol engine
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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,
I still have the original ballasted coil in my car with the original wiring & relay set up & starter motor with attached solenoid that has the additional terminal marked IGN that cuts in and supplies full voltage to the coil when cranking.
Without removing it i can't read what is stamped on the end as it is angled in towards the inner wing. (I did make a note of it somewhere when i last removed it , but don't recall where i filed the note). However I'm sure it is a Lucas / 16C6 that has a primary resistance of 1.43 to 1.58 ohms & a secondary of 1.3 to 1.4 ohms that you also refer to , notwithstanding my MGB repair manual for UK Spec shows the HA12. (Sometime ago out of interest i did check the resistance & it tallied with the 16C6). There are many known errors in the various official publications which were obviously subject to periodic updates from time to time - the wiring diagrams being a case in point. (I also suspect the usual running range Voltage of the coil is possibly identifiable by the ref HA "12" for 12 Volts & 16 C"6" for 6 Volts ! (The ballasted system was i believe introduced when the RBs came in).
I do wander if Beech's set up had been modified to use the starter relay in some way to replace the action of the IGN terminal on the back of the starter motor if the motor had been changed at some time with an earlier pre - RB type that didn't have the additional IGN terminal or one of a more modern efficient types that also does not have the additional IGN terminal . ( I believe the later versions are hard to come by).
The mystery continues!
Cheers,
Charles
1980 Roadster
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