Morris Minor Owners Club

Posted: **Sat Feb 14, 2026 1:53 pm**

Hello,

I took my Morris for a little run out today and as I got home I flicked the headlights on and the entire car just died.

My interior light turns on, but weirdly goes off when I try and switch the lights, turn the ignition or try to sound the horn…

Does this sound like anything you’ve come across before?

Thanks,
James

Posted: **Sat Feb 14, 2026 2:50 pm**

Clean the battery terminal posts and terminal clamps. Replace, tighten, try again.

Stephen

Posted: **Sat Feb 14, 2026 3:43 pm**

svenedin wrote: ↑Sat Feb 14, 2026 2:50 pm Clean the battery terminal posts and terminal clamps. Replace, tighten, try again.

Stephen

I did wonder about this, but I have other lights that work (the interior light). I also have a new circuit that runs from my solenoid which powers my hazards, and they’re working fine so I’m assuming I have decent battery/connections.

Posted: **Sat Feb 14, 2026 3:54 pm**

radioactiveman wrote: ↑Sat Feb 14, 2026 3:43 pm
svenedin wrote: ↑Sat Feb 14, 2026 2:50 pm Clean the battery terminal posts and terminal clamps. Replace, tighten, try again.

Stephen
I did wonder about this, but I have other lights that work (the interior light). I also have a new circuit that runs from my solenoid which powers my hazards, and they’re working fine so I’m assuming I have decent battery/connections.

The interior light is a tiny little bulb that draw a small current. The headlights draw much more current and the starter a lot more still. With a poor battery connection, often there is enough power to light a small bulb but not enough for any significant current draw. As you have seen, your interior light goes out as soon as you try to add more load. You could already have cleaned up the battery connections in hardly more time than it took to think about it. Another possibility is your battery is nearly but not completely flat +/- a bad connection as well.

Stephen

Posted: **Sat Feb 14, 2026 4:06 pm**

svenedin wrote: ↑Sat Feb 14, 2026 3:54 pm
radioactiveman wrote: ↑Sat Feb 14, 2026 3:43 pm
svenedin wrote: ↑Sat Feb 14, 2026 2:50 pm Clean the battery terminal posts and terminal clamps. Replace, tighten, try again.

Stephen
I did wonder about this, but I have other lights that work (the interior light). I also have a new circuit that runs from my solenoid which powers my hazards, and they’re working fine so I’m assuming I have decent battery/connections.
The interior light is a tiny little bulb that draw a small current. The headlights draw much more current and the starter a lot more still. With a poor battery connection, often there is enough power to light a small bulb but not enough for any significant current draw. As you have seen, your interior light goes out as soon as you try to add more load. You could already have cleaned up the battery connections in hardly more time than it took to think about it. Another possibility is your battery is nearly but not completely flat +/- a bad connection as well.

Stephen

Yes, you make a good point! I will check that out.

Posted: **Sat Feb 14, 2026 4:10 pm**

Just had a think about this especially as you mentioned a new circuit from the solenoid.

All of the car's electrics are powered by one wire that comes off from the solenoid. It's the big brown wire in the photo. Check that!

Stephen

: IMG_2653.jpeg (1.57 MiB) Viewed 267100 times

Posted: **Sat Feb 14, 2026 6:00 pm**

To add some more information, if I push the solenoid button the engine turns over so there’s plenty of juice in the battery.

Posted: **Sat Feb 14, 2026 6:08 pm**

Is there power upto the fuses, it uses the connection as a junction for non fused circuits.

Posted: **Sat Feb 14, 2026 6:20 pm**

radioactiveman wrote: ↑Sat Feb 14, 2026 6:00 pm To add some more information, if I push the solenoid button the engine turns over so there’s plenty of juice in the battery.

Ok good. Is the contact clean and secure from the solenoid to the brown wire? The brown wire goes from the solenoid to terminal A of the RB106 control box so check there as well. Then a brown and blue wire goes from terminal A1 to the lighting switch. The power to the headlights is permanently live and not fused.

In the diagram Solenoid=21 RB106=11 N=brown wire NU=brown/blue wire 20=battery 22=starter motor

Stephen

: Screenshot 2026-02-14 at 18.16.57.png (36.38 KiB) Viewed 267016 times

Posted: **Sat Feb 14, 2026 7:27 pm**

svenedin wrote: ↑Sat Feb 14, 2026 6:20 pm
radioactiveman wrote: ↑Sat Feb 14, 2026 6:00 pm To add some more information, if I push the solenoid button the engine turns over so there’s plenty of juice in the battery.
Ok good. Is the contact clean and secure from the solenoid to the brown wire? The brown wire goes from the solenoid to terminal A of the RB106 control box so check there as well. Then a brown and blue wire goes from terminal A1 to the lighting switch. The power to the headlights is permanently live and not fused.

In the diagram Solenoid=21 RB106=11 N=brown wire NU=brown/blue wire 20=battery 22=starter motor

Stephen

Screenshot 2026-02-14 at 18.16.57.png

I went out, removed the brown wire and reinstalled it. Suddenly there was life… How embarrassingly simple. Thank you!

I’m a little confused as to what happened. I wonder if the connection was good enough to start the car but at some point on my drive the connection was lost… Which was fine until I asked for dipped beams at idle and then it just didn’t have enough juice to continue.

Posted: **Sat Feb 14, 2026 8:59 pm**

radioactiveman wrote: ↑Sat Feb 14, 2026 7:27 pm
svenedin wrote: ↑Sat Feb 14, 2026 6:20 pm
radioactiveman wrote: ↑Sat Feb 14, 2026 6:00 pm To add some more information, if I push the solenoid button the engine turns over so there’s plenty of juice in the battery.
Ok good. Is the contact clean and secure from the solenoid to the brown wire? The brown wire goes from the solenoid to terminal A of the RB106 control box so check there as well. Then a brown and blue wire goes from terminal A1 to the lighting switch. The power to the headlights is permanently live and not fused.

In the diagram Solenoid=21 RB106=11 N=brown wire NU=brown/blue wire 20=battery 22=starter motor

Stephen

Screenshot 2026-02-14 at 18.16.57.png
I went out, removed the brown wire and reinstalled it. Suddenly there was life… How embarrassingly simple. Thank you!

I’m a little confused as to what happened. I wonder if the connection was good enough to start the car but at some point on my drive the connection was lost… Which was fine until I asked for dipped beams at idle and then it just didn’t have enough juice to continue.

Simple solutions are good solutions!

Yes just a bad connection. Loose, bit of corrosion, who knows. Maybe the vibrations of the car in motion made the connection worse.

Glad it's fixed. Happy motoring!

Stephen

Posted: **Sun Feb 15, 2026 12:00 pm**

Without getting all technical and going into Ohms Law, what happens if there is a 'high resistance' in a circuit which shouldn't be there? The effect it has is dependant on how much current (amps) is going through it.
When that high resistance is at a point that is common to several circuits, in this case the supply to everything, the more you turn on the greater the problem.

radioactiveman wrote: ↑Sat Feb 14, 2026 1:53 pm I took my Morris for a little run out today and as I got home I flicked the headlights on and the entire car just died.
My interior light turns on, but weirdly goes off when I try and switch the lights, turn the ignition or try to sound the horn…

So using made entirely up numbers just to illustrate the principle, let's say while you were driving around, the only thing that was drawing power was the Coil to run the engine, and the voltage drop at the poor connection was 2v; the Coil will still be happy with the 10 volts that it's getting.

You turn on the headlamps and the extra current through that high resistance now causes a voltage drop of 4v so the Coil is now only getting 8v and it dies.

You turn the interior light on and a similar thing, as Stephen says, only a tiny current required so the voltage drop is small.
You try the Horn, the current draw is high, therefore the voltage drop at the poor connection is high and the horn doesn't get enough.

Posted: **Sun Feb 15, 2026 3:12 pm**

Confucius the famous Chinese electrician says:
"The less you have, the smaller the portion gets, the more it's shared amongt"

Posted: **Mon Feb 16, 2026 10:13 am**

geoberni wrote: ↑Sun Feb 15, 2026 12:00 pm Without getting all technical and going into Ohms Law, what happens if there is a 'high resistance' in a circuit which shouldn't be there? The effect it has is dependant on how much current (amps) is going through it.
When that high resistance is at a point that is common to several circuits, in this case the supply to everything, the more you turn on the greater the problem.

radioactiveman wrote: ↑Sat Feb 14, 2026 1:53 pm I took my Morris for a little run out today and as I got home I flicked the headlights on and the entire car just died.
My interior light turns on, but weirdly goes off when I try and switch the lights, turn the ignition or try to sound the horn…
So using made entirely up numbers just to illustrate the principle, let's say while you were driving around, the only thing that was drawing power was the Coil to run the engine, and the voltage drop at the poor connection was 2v; the Coil will still be happy with the 10 volts that it's getting.

You turn on the headlamps and the extra current through that high resistance now causes a voltage drop of 4v so the Coil is now only getting 8v and it dies.

You turn the interior light on and a similar thing, as Stephen says, only a tiny current required so the voltage drop is small.
You try the Horn, the current draw is high, therefore the voltage drop at the poor connection is high and the horn doesn't get enough.

This is very interesting, thank you. I've asked the internet to explain it to me and my head is now full of analogies to do with hosepipes.

Posted: **Mon Feb 16, 2026 7:52 pm**

radioactiveman wrote: ↑Mon Feb 16, 2026 10:13 am
This is very interesting, thank you. I've asked the internet to explain it to me and my head is now full of analogies to do with hosepipes.

Yes, a lot of similarities when trying to explain things, the electricity being like pressure in a hose, the difference is it doesn't come out if you cut through it...

It's all down to Ohms law and resistors, whether in Series or Parallel.

Posted: **Tue Feb 17, 2026 9:07 pm**

geoberni wrote: ↑Mon Feb 16, 2026 7:52 pm
radioactiveman wrote: ↑Mon Feb 16, 2026 10:13 am
This is very interesting, thank you. I've asked the internet to explain it to me and my head is now full of analogies to do with hosepipes.
Yes, a lot of similarities when trying to explain things, the electricity being like pressure in a hose, the difference is it doesn't come out if you cut through it...

It's all down to Ohms law and resistors, whether in Series or Parallel.

Cutting a hose is exposing the flow to an easy route to a low pressure environment. So the electrical analogy is shorting a conductor to chassis.
Sometimes the high resistance faults as experienced by the OP can be bit more complicated than just V=IR. A single - perhaps corroded - strand may heat up when asked to carry a larger current. And hot wires (as in bulb filaments) have higher resistance than when cold. In other words, Mr Ohm is still right, but in flakey Minor connections R can vary with I.
Bottom line: keep a multimeter in your tool kit.

Posted: **Tue Feb 17, 2026 10:16 pm**

mike1864 wrote: ↑Tue Feb 17, 2026 9:07 pm
And hot wires (as in bulb filaments) have higher resistance than when cold. In other words, Mr Ohm is still right, but in flakey Minor connections R can vary with I.
Bottom line: keep a multimeter in your tool kit.

Ohm’s Law is often simply stated in letters, like V=IR. In words, it does state ‘at constant temperature’.

The full voltage (EMF) will be shared between the resistances, in series, in a direct relationship. The largest resistance will simply drop the largest share of the voltage across itself. Yes, easily checked with a multimeter. In electronics it is often termed/used as a potential divider.

Posted: **Wed Feb 18, 2026 12:19 pm**

mike1864 wrote: ↑Tue Feb 17, 2026 9:07 pm
Cutting a hose is exposing the flow to an easy route to a low pressure environment. So the electrical analogy is shorting a conductor to chassis.

That's really stretching the analogy concept.

Water will just P*ss out all over the floor, the electrical cable won't leak electricity.....

Posted: **Wed Feb 18, 2026 12:33 pm**

geoberni wrote: ↑Wed Feb 18, 2026 12:19 pm
mike1864 wrote: ↑Tue Feb 17, 2026 9:07 pm
Cutting a hose is exposing the flow to an easy route to a low pressure environment. So the electrical analogy is shorting a conductor to chassis.

That's really stretching the analogy concept.
Water will just P*ss out all over the floor, the electrical cable won't leak electricity.....

Its usually smoke leaking out

Posted: **Wed Feb 18, 2026 12:55 pm**

Bill_qaz wrote: ↑Wed Feb 18, 2026 12:33 pm
geoberni wrote: ↑Wed Feb 18, 2026 12:19 pm
mike1864 wrote: ↑Tue Feb 17, 2026 9:07 pm
Cutting a hose is exposing the flow to an easy route to a low pressure environment. So the electrical analogy is shorting a conductor to chassis.

That's really stretching the analogy concept.
Water will just P*ss out all over the floor, the electrical cable won't leak electricity.....
Its usually smoke leaking out

And we all know that when the special Lucas smoke leaks out nothing works again!

Stephen

Morris Minor Owners Club

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