Blown Fuse?

[SV_Minor]

I'm up in Scotland on a touring holiday and earlier today my indicators and horn stopped working. I know everyone has likely wired indicators in to their own car in their own way, but I'd imagine the Minor horn is wired the same in all Minors. Can anyone give me a pointer where/what to look for? Thanks in advance.

[Ian Grace]

Hi Jonathan,

Here's the '33 Minor wiring diagram showing the wiring of the horn. Basically, the horn takes 6V from the + terminal on the cut-out and the switch connects the other pole of the horn to earth. Hope this helps, and good luck with the rest of the trip. Any chance of a bit of a report here, or for the Magazine?

[SV_Minor]

Thanks Ian. Looks like I've discovered the real issue. The dynamo appears to not be charging the battery. I've managed to travel 160 miles today, now in the Lake District to the west of Penrith. So far the issue hasn't impacted on the 'engine management system' so I haven't come to a stop on the side of the road with a dead car yet... thankfully. I've had a look under the bonnet but nothing is looking obviously out of place. That's as far as my knowledge stretches.

[SV_Minor]

I should have mentioned that I did a voltage check on the battery, with engine running, just south of Glasgow earlier. The reading was 6.02v. I've since done another reading, this time without the engine running, after I arrived at the B&B. The battery was sitting at 6.29v, though the engine had only been shut down for an hour or two. It'll likely show a drop overnight. I'll attempt to swing the engine into life on the starting handle in the morning. Give the battery the best chance of getting me home.

[SV_Minor]

Well, it all went t*ts up yesterday. Broke down just east of j36 M6 with a flat battery. RAC came out and spent two hours on the car and declared it good to go. I managed another 103 miles, with just 68 miles remaining, when I threw in the towel and called the RAC for a tow home. The LED headlamps won't function below 6v, battery was hovering around 5v. I had to wait over 8hrs in not pleasant conditions. Finally arrived home at 4am this morning. The car is now in the dog house.. um, garage, until I have time to take a look at it. 954 miles done under its own steam. Would have been about 1,020 miles if I'd managed to complete the journey.

[Ian Grace]

That's a great shame, Jonathan, but well done for getting so far and under much less than ideal conditions.

Hopefully it won't take much to sort the charging issue.

[SV_Minor]

Thanks Ian. I've noticed the ignition light isn't functioning, so is that a pointer to the problem? I'm wondering if the bulb is in series so if it has blown it breaks the circuit.

[SV_Minor]

I've just been looking at your image above for the 1933MY. I'm guessing it's pretty much the same on my 1932MY car, so it looks like one wire to the ignition lamp comes in from the D-post on the back of the PLC. Tracing other wires that share that connection brings me to the D+ on the dynamo. Following the other wire from the lamp takes me to the IG-post on the back of the PLC, which shares it with the ignition coil. So it can't been in series then, surely?

[Ian Grace]

Yes, I'm pretty sure the 1932 and 1933 MY wiring diagrams are the same. This diagram is the original from Morris, so is accurate.

So IG has 6V on it when the ignition is on and the +D is the voltage coming from the dynamo. When the dynamo is putting out 6V (on +D), the ignition lamp will have no voltage across it so will be out. If the output from the dynamo drops, then the light comes on.

(That is actually +D on the PLC, not D.)

Not sure if any of this helps!

[SV_Minor]

Definitely helpful, thanks. A few things; I have a battery isolator fitted, and when I reconnect the battery I usually hear a click from somewhere (cut-out?). I haven't been getting that click over the past few days I've been getting the problems with. Secondly; the ignition lamp is dead with the ignition switched on, with and without the engine running. I'm hoping the cut-out hasn't jammed shut and turned the dynamo from a generator into a motor, hence the flat battery. Would such a thing blow the ignition warning bulb? I'm hoping it isn't that, that is the issue My knowledge doesn't run deep enough to figure out what is going on.

[SV_Minor]

I'll just add I've recharged the battery and it's now showing Fully Charged on the smart-charger screen. Hopefully find it hasn't been ruined by running at 4v.

[Ian Grace]

I doubt if anything would blow the warning light bulb, as that would imply 12 volts got across it somehow. I don't think that is possible.

Can you under the bezel on the lamp, pull the bulb out and eyeball the filament?

[Ian Grace]

Unless it is a really old battery, running it down won't damage it at all.

[SV_Minor]

I doubt if anything would blow the warning light bulb, as that would imply 12 volts got across it somehow. I don't think that is possible.

Can you under the bezel on the lamp, pull the bulb out and eyeball the filament?

That's good to know. I'll have a look at pulling the bulb out later. Is there anything else I can look at?

[SV_Minor]

Unless it is a really old battery, running it down won't damage it at all.

I'd say it's around 5-6 years old and has powered the car for the past 14k miles.