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MG Midget and Sprite Technical - No electrics - Frogeye and early Midget relevance

I'm currently visiting my wife's brother in Aberdeen. He has a fifties Morris Minor, and since he knows nothing about cars he has asked me to try and find out what's wrong. As the electrics are basically the same as a Frogeye, I hope someone can help.

The car has positive earth. The battery is brand new and fully charged. All battery connections are clean and tight. But all electrics are dead. When you open the door the interior light comes on at a slight glow, and as soon as you try to switch on anything else it goes out. No electrical items work at all.

Using a cheap multimeter and the Haynes manual I can trace 12v from the brown wire on the starter solenoid to terminal A on the regulator box and from there to the top fuse and across the fuse to the purple wires on the other side of it. I have removed the fuse and cleaned it and its holder.

Haynes shows that those purple wires go to the interior light and the horns, and nowhere else. I have traced connection to the left horn and to the interior light and both seem ok. The system is so dead that not even the ignition warning light or the fuel gauge come on.

All this is beyond my pay grade som can someone more knowledgeable (and that means almost all of you) give me a clue as to what to do next. Thanks.
Mike Howlett

Could it be something like a really poor earth on the positive battery connection to the body?
Jeremy MkIII

Mike, does this car have the 4 fuses, fuse box?

If so, then you may find it has been fitted the wrong way round and your brown feed cable also has a permanent connection to the adjacent fuse and therefore to whatever that fuse is feeding, which might give a clue where to look.
The connection is hidden on the underside of the fuse box.

If it doesn't have the 4 way fusebox, then just ignore this speculation!
GuyW

I've checked and cleaned the earth connection for the positive battery lead, but thanks for the suggestion.

Guy the car is virtually in original condition having been bought new by my brother-in-law's aunt and passed on to him when she died. It only has two fuses.

I think I must start by disconnecting circuits one by one until the problem clears. Then I might have some idea where the problem lies. There has to be short circuit somewhere I think.
Mike Howlett

Mike,
the wiring on this will be almost the same as an early MGB if you need a diagram to refer to.

Most of the electrics will be live direct from the battery e.g. interior and exterior lights, radio if fitted in the original way. The only things switched by the ignition switch are the fuel pump, ignition (obvs) and things on the green circuit (brake lights, indicators, heater fan, wipers etc)

So, where to start... I would take the brown wires off the regulator box and connect them together. That will eliminate the regulator and the dynamo from the equation. Then you need to check what voltage you are getting at the interior light, both sides of the fuse, back at the brown wires you've disconnected at the regulator and at the solenoid. Do these measurements with a load on e.g. the interior light and keep a close eye out for anything getting hot.

I'm guessing it'll be around 6V at the lamp and will go to 12v at some point closer to the battery. If you have less than 12v at the battery it dead!

What I think you're looking for is a high resistance connection/wire probably the one from the solenoid to the regulator.

Best of...
MGmike

PS. if all else fails I'm only 2hrs away and very reasonable rates ;O)


M McAndrew

Oh, and if everything comes to life when you disconnect the wires from the regulator, you have a problem in that or the dynamo ;O)
M McAndrew

I don't think you have a short anywhere - If the battery is full there would be smoke leaking out somewhere.
More likely to be a bad connection somewhere -- battery terminals, dead battery
Try measuring the voltage at the brown on the solenoid, you mentioned you had 12v there, then try turning the key on or turning the headlights on, it should stay close to 12v -IF the voltage drops right off there is a faulty/loose connection either at the battery ,at the solenoid, or the wire between.
IF the 12v is healthy at that Then put one end of your meter to earth, pull your headlights on and turn the ign. on and follow that brown wire checking for 12v everywhere as you go, there has to be a dodgey connection there that drops power with load.--having the lights/ign on should show that up.
Or just do the wriggle test, pull the lights on and wriggle the wiring one wire at a time near the solenoid /fuse box, battery etc until the lights light up when you find the faulty connection.
willy

William Revit

Thank you guys. Mike, it isn't quite the same as the early MGB - I have both the diagram for the Minor in Haynes, and the MGB one on the Autosparks PDF. The regulator on the Morris is marked A1, A, F, D and E. The MGB is labelled B, F, W, D and E, and the wire colours aren't exactly the same.

On the Minor there is a single brown wire from the solenoid to terminal A. From A a single brown goes to the top fuse and then to the interior light and horns by purple wires.

Next to terminal A is A1. That has two brown/blue wires going to the ignition switch and to the light switch.

The other terminals on the regulator are F with a single yellow/green to the dynamo, D with two yellows to the ignition warning light and the dynamo, and finally E which is earthed.

When you say join the browns together, do you mean join the browns and brown/blues (that is A to A1) together?

My initial thought is to remove the top fuse (the purple circuits) and see if the green circuits then work.The function of the regulator is a mystery to me and this recently occurring problem is taxing my knowledge.

I hope you are free this weekend :))))). By the way the car is actually a 1963 Minor 1000.

Willy, I haven't checked what you mention. I have to go out with Mrs H and her brother today, but I'll give it a go once we are back.

Really appreciate your inputs gents.
Mike Howlett

I don't know if this helps. Poor quality photo taken on laptop camera.


Mike Howlett

Mike

Like the frogeye the side/headlights are not fused so should come on regardless of the ignition is on or off
A dim light interior light suggests a bad connection somewhere.
Most of the ancillaries eg wipers/indicators/brake light are via the green wire to the fuse box. the other fuse controls the horns and interior light.

its worth cleaning the terminals on the regulator, ie slacken and retighten the screws holding the wires to A and A1.
Bob Beaumont

Might the starter solenoid be in the on position, and the starter Jammed. Turning on the ignition would feed power to the jammed starter, taking all the power and dimming the lights etc.
GuyW

I think Guy's thinking is along similar lines to mine.
I think I'd start with disconnecting the starter first, then the solenoid connection from the battery. Dead easy to do and I always advocate eliminating the simple stuff first.
See if either one makes a difference. Both are notorious for subtle leaks.
DISCLAIMER: My arthritis is giving me proper grief so I'm off my face on the painkillers. If I've said something stupid give me a break, eh!
🥴
Greybeard

having the lights on and the key on is a good basic test for current draw---if the lights are bright the battery connections should be good -if they're dull or not working it's probably a dud battery or connections
if the lights are good but no ignition it's going to be something to do with the power supply either to/from the brown wire from the solenoid to the fuse block.
It's weird that you've got 12v at the brown wire at the fuse block but a dull inside light----if it has 12v out the other side of the fuse and through the connector to the purple wire to the inside light then the light should be bright. that area needs to be checked for 12v at the connections-
William Revit

I had a similar problem on the Frogeye. It took me two whole days to fix it. The control box (a relatively new one) has the connections riveted on the underside. One of them had corroded, and could only pass very low current. Hence I could not diagnose it with a test meter. I replaced the rivet with a screw and all was well.
Les Rose

Mike,
principle of operation is the same. You'll probably find the A & A1 terminals are connected together on the bottom of the regulator. Disconnect and join those cables on A & A1 to isolate the regulator and Dynamo from the issue at hand.

I'll PM you my number if you want to call me tomorrow.

Best of...
MGmike

M McAndrew

Mike, tried to send you a message but (failed miserably) you've blocked incoming messages. Can you message me or add me as a friend and I'll respond with a number.

Best of...
MGmike
M McAndrew

Mike McA, I think I have sent you a message telling you my mobile number for sms or whatsapp, and my email. One of those should work.

I got an hour or so later this afternoon and had another look at the Minor. The trouble is everything under the bonnet is old and corroded and just plain grotty. I have had the fuses out and cleaned them and their holders as best I can. I tried disconnecting the browns from terminal A and the brown/blues from A1 connected them together with some short lengths of copper wire. It didn't make any difference. With everything off, the battery shows 11.8v and I trace that right through to the output side of the top fuse. As soon as you open the door it drops to around 7v.

I removed the top fuse thus disconnecting all the purple circuits (interior light and horns) Reconnected the battery and tried switching on the ignition. The red warning lamp glowed very dimly and we were back to 7v again. Tried the same experiment and this time switched on the side lights. They glowed very dimly and back to 7v we were.

Tomorrow I will try remaking the earth connection from the battery. It has been off recently and looks clean and the bolt is tight, but I'm all out of ideas so I'll try anything.

I have to go back home on Monday and would love to be able to sort this out for Geoff before I go, but I really don't have any idea how to achieve that. The car hadn't been started for several weeks prior to this, but the battery has been on a smart charger the whole time.
Mike Howlett

Had a similar problem with a Ford Sierra many years back where the cause was found to be the main +ve power lead connection to the battery with significant 'white' growths between the copper cable and lead terminal.
Dis-assembly of the connection with thorough cleaning and soldering the original crimped connection resolved the problem.
S G KEIL

Where are you attaching the meter leads when you’re getting 7v?
Dave O'Neill 2

Dave, I am putting the pos lead on the battery earth connection and the neg lead on whatever I'm checking, solenoid, fuse, control box terminal, etc.
Mike Howlett

Yep there's your answer. Supply current is limited by resistance caused by corrosion. Either at one or both battery post connections, or at the main earth to chassis, or at the first live distribution/junction point(s), or since you've now said under bonnet has a lot of corrosion, then likely every electrical connection is suspect, and needs cleaning.

Start at the battery posts, and work out from there.

Tedious and time consuming though it is, consider it a labour of love rather than a chore. 😉

Just double checking. Are you certain you have full battery voltage at the battery posts and clamps?

anamnesis

I agree with Anam and others. Remove, check and clean (brighten up the metal) of connections between battery -ve and A/ A1 on reg. and battery +ve to body. Then try it. If it starts, also worth cleaning up other reg connections and at fuse terminals. Also if you can poke a test lead into the metal part of the cable adjacent to battery -ve (and battery +ve) this would test SG Keil's suggestion (maybe do this first).
Bill Bretherton

Mike
it really sounds like a dead battery
to test--
Connect your meter to the actual battery posts themselves-not the cables then pull the lights on, if the voltage drops to the 7v that you've been getting then the battery is either flat or dead.
If the battery voltage stays up (app.12v) then you have a connection problem----in this case, with the lights on,if you leave the meter connected to the neg terminal of the battery then the pos.lead to body earth you should get the same battery power reading (app.12v)- If it's the 7v then you have a bad earth connection from the battery to earth.
Then round the other way ,meter on the battery pos terminal and the other lead to the neg post connector, cable to the solenoid,brown wire to fuse block, both ends of the fuses and out to the other side of the fuse block should all be battery voltage--If there's a drop down to that 7v as you work your way outwards from the battery then that is where the resistance is.
BUT check that battery first - it does have the symptoms of a dead battery
willy
William Revit

Willy, this morning's efforts have proved you right. Despite being reasonably new, and on a smart charger all the time, the battery is absolutely knackered. After being on charge all night I disconnected it from the car by removing both leads. The voltage read 12.4v which seems OK. But then I put a light load on the battery by connecting to it my tyre inflator, much less than a 5 amp load. The inflator didn't even try to operate and when I checked across the battery terminals it was down to 0.6v.

I pulled my trusty VW across to it and connected up the jump leads and it started immediately. It runs fine while the fast idle is on, but as soon as you push the choke right in so the dynamo isn't producing much juice, the engine stalls. Doh, I've been messing with cars for over 50 years and yet I seem never to look for the most obvious solution first.

A huge thanks to everyone who contributed. This forum is a treasure. I feel I know some of you even though we have never met. Good on ya guys!
Mike Howlett

Mike
Glad you've found the problem. Because you'd originally said the battery was "brand new and fully charged" I guess most of us here assumed the battery was good. Never assume....
Bill Bretherton

Yes Bill, I was told it was "nearly new" and as it came off the charger with 12.4v I took that statement at face value - and wasted 2 days of my time. Start checking from first principles !!! Bought a new battery this afternoon and it starts like a champion.

Mike Howlett

Good job Mike- Problem is you've fixed it too early, now you've got time for some other jobs before you head home lol.
Just a point on batteries that you probably already know. They hate sitting on concrete floors, If the battery had been out sitting on a concrete floor for ages on a trickle charger the concrete floor would have killed it for sure--I don't know why but it does.
Years back we used to buy about 50 batteries at a time and stack them up against the wall in the w/shop, and by the time the bottom row got used they would be dead, Thought it was just dud batteries for a while (they were cheapies afterall) but it happened a few times before the battery supplier mentioned the concrete thing--Used some timber planks under them and fixed the issue. How a battery knows what it's sitting on is beyond me but as we know if it's to do with a car, it's trouble.
Cheers
willy
William Revit

And keep in mind that, you can't tell the *condition* of a battery using a digital volt meter alone. They draw almost no current. It can be fully charged, but still be knackered; fully charged to its remaining capacity that is. So misleading.

Terminal voltage using your MM, 12.4 Volts. But as soon as you draw current, that voltage drops significantly due to resistance. Not external corrosion resistance. But internal resistance. Sulphated plates.

I keep my batt' off cold floors too Willy. Always have. A low/part charged battery is damaged by the cold, whereas, a fully charged battery can stand freezing conditions/temperatures. Something to do with chemistry I think. And I'm no chemist.

anamnesis

Thanks Anam, I knew the MM wasn't any measure of condition, which is why I put a light load in the shape of my tyre inflator on the battery. As I mentioned that killed it stone dead.

Willy, the concrete thing is interesting. As soon as I get home I'm moving my spare battery off the floor onto some wood! However the duff battery was in the Morris all the time so we can't blame that.
Mike Howlett

This thread was discussed between 03/10/2024 and 06/10/2024

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