Blowing Fuses Constantly

[Andymoor94]

Hello!

1954 Series 2 four door

So I've had a problem on and off but now it's become much more apparent. In fact, every time I turn the ignition, my "luxuries" fuse blows, leaving me without a heater, trafficators, brake lights, wipers, fuel gauge, interior lighting. The fuse I originally used was 15A, then upped to a 25A and have now read that 35A is the standard, but at the risk of having a fuse that doesn't blow (instead, burning a wire somewhere), I've not put one in yet.

Now I get that this could well be a short happening somewhere, but in order to even have the motivation to start searching through the wiring, has anybody got any useful documentation that can help me? I'm not incredibly electrically inclined, doing only basic wiring for my mopeds, which are simple circuits.

Any further help with this would be super appreciated too!

[les]

If a 35 amp fuse is correct, then it might be reasonable to suspect that a lower value was considered likely to blow too soon by the designers. Perhaps a start would be to make sure all the ‘luxuries’ are not active before you turn the ignition. If by some chance all is ok, then activating each circuit one at a time might pinpoint the area to concentrate on. There are people more experienced in electrical stuff here than me that will be more capable in going further.

[geoberni]

Why was there a 15A in there?
The standard for both the Moggie Fuses is 35A.
Simple as that.

[Andymoor94]

Why was there a 15A in there?
The standard for both the Moggie Fuses is 35A.
Simple as that.

Not sure, it came with 15A when I bought it and ran with only intermittent blowing (likely when I used many electrics at once, thinking back).

[jagnut66]

Hi,
I have fitted inline fuses to anything I have 'added'. As Berni says, the 35 amp fuse was standard fitment throughout the Minors production run, though others have added additional fuse boxes over the years to separate out lights etc.
If that is what you want to do then start a fresh post requesting help to install an updated fusebox, there are others on here that will have the knowledge to help you with this.
Best wishes,
Mike.

[Andymoor94]

Hi,
I have fitted inline fuses to anything I have 'added'. As Berni says, the 35 amp fuse was standard fitment throughout the Minors production run, though others have added additional fuse boxes over the years to separate out lights etc.
If that is what you want to do then start a fresh post requesting help to install an updated fusebox, there are others on here that will have the knowledge to help you with this.
Best wishes,
Mike.

Hi Mike,

That won't be on the cards for a long time - Maybe not until the wiring turns into dust!

But yeah, it definitely seems that my issue could well be just a fuse that's too small. I've got new fuses on their way, so will try that and see how I get on.

[oliver90owner]

All such fuses are there to protect the down-stream wires/leads/connections. A 35A fuse will likely only blow if there is a dead short. Seriously overloading any circuit wiring is likely to lead to a fire.

Think here of your house circuits - the plug fuse only protects the lead from the plug to the appliance, nothing more. If you have ever seen the outcome of wiring an appliance, drawing 13A, with only lighting flex, you would most certainly understand the risk.

It is why modern vehicles have rather more fuses than these vehicles built long ago.

[geoberni]

Why was there a 15A in there?
The standard for both the Moggie Fuses is 35A.
Simple as that.

Not sure, it came with 15A when I bought it and ran with only intermittent blowing (likely when I used many electrics at once, thinking back).

OK, so there are basically 2 reasonable reasons for that, before we go into guessing at any more obscure or off-the-wall fantasies.

Either,
A) the previous owner didn't have a clue about fuse ratings and just put any random fuse in that came to hand
or,
B) they had a wiring problem and rather than sort it out stuck a smaller fuse in.

What's the wiring condition like?
What's slightly worrying me here is that you were running it and a 15 ruptured occasionally, but now a 25 is doing the same continually.....
which would imply the situation has worsened.

To be on the safe side, before putting a 35A in, I'd disconnect all the connections from that fuse and (assuming you haven't got an insulation tester, but hopefully have a multimeter), I'd check each line for it's resistance value*. If one of the lines comes up at less than 0.5 Ohms, you've most likely got a problem on that line.

*That's measuring the resistance from each of the connections, individually, to earth on the bodywork
Just in case you don't know what I'm talking about.

[Andymoor94]

Why was there a 15A in there?
The standard for both the Moggie Fuses is 35A.
Simple as that.

Not sure, it came with 15A when I bought it and ran with only intermittent blowing (likely when I used many electrics at once, thinkia multimeter
OK, so there are basically 2 reasonable reasons for that, before we go into guessing at any more obscure or off-the-wall fantasies.

Either,
A) the previous owner didn't have a clue about fuse ratings and just put any random fuse in that came to hand
or,
B) they had a wiring problem and rather than sort it out stuck a smaller fuse in.

What's the wiring condition like?
What's slightly worrying me here is that you were running it and a 15 ruptured occasionally, but now a 25 is doing the same continually.....
which would imply the situation has worsened.

To be on the safe side, before putting a 35A in, I'd disconnect all the connections from that fuse and (assuming you haven't got an insulation tester, but hopefully have a multimeter), I'd check each line for it's resistance value*. If one of the lines comes up at less than 0.5 Ohms, you've most likely got a problem on that line.

*That's measuring the resistance from each of the connections, individually, to earth on the bodywork
Just in case you don't know what I'm talking about.

I have a multimeter! First time doing this, so how would I got about testing each line?

FYI, I did put a 35A in, before reading your comment. Also burst, so there's a short somewhere.

Condition of wiring is old, of course, but it's not damaged, corroded, etc. The wires are still even flexible!

The only thing I remember from the previous time was my left trafficator being involved in my concerns. Very sensitive switch when activating the left one, but right one was fine, so I may well take that switch off and investigate there. Not sure what I'd be looking for other than corrosion or terminals/wires very close to each other.
I removed the trafficator yesterday and found a thick steel cable had snapped (was coiled round the upper screw). Not I know this is a headliner cable, nothing electrical, but oddly enough, the last time this problem occured, I removed, cleaned and greased both trafficators and the issue disappeared. This has only come about now after the car was sat for 3 weeks, awaiting the wheels to return from coating and new tyres.

[Andymoor94]

Here's an image of my fuse and connections. How would I go about testing?

[geoberni]

Hi
sorry for the delay in coming back to you, it's been a terribly turbulent day for several reasons. So I'm only just catching up on things.
Meanwhile, you've posted a photo, so that's a help actually. Looks very original.

The lower fuse is presumably the one you're having a problem with.
Electricity is funny stuff, it will always find a way to complete the circuit if it possibly can, so when fault finding it's important to eliminate stray return paths.
In this case, we're looking at the lines connected to 2 terminals 'A4', the bottom Right and via the green link the Centre bottom.
The 3 wires on the lower Left are (hopefully) the unfused items and the feed to the fuse.

Start off with removing the fuse, unless it's still ruptured This is to ensure we don't get those pesky return paths we're not expecting.

Other than the green link, those cables are going off to the fused items on the switched live.
Undo those 2 screws and separate out the cables (remembering where you put the green link for later when you want to refit it )
Using the multimeter, set to Ohms, check each of those cables by having the black meter lead to the body metal work (or the earth on the battery) and then touching each of the individual lead ends with the red meter probe.
One of them is hopefully going to be well under 1 ohm. That's the problem one.

I can't be too specific because many Minors have had wiring changes made over the years, but for example it might be the trafficators. So when doing these 'resistance checks, you'll need to operate switches such as the horn, trafficators, interior light heater, blower rheostat, to see if they make a difference.
I suspect it may well turn out to be one of the trafficators, due to their electro-mechanical action.

I hope I've make that an easy enough description for you, any problems please come back and ask for clarification; it's easy for me to miss something that's 'obvious' to me with a lifelong electrical background.

[Andymoor94]

Hi
sorry for the delay in coming back to you, it's been a terribly turbulent day for several reasons. So I'm only just catching up on things.
Meanwhile, you've posted a photo, so that's a help actually. Looks very original.

The lower fuse is presumably the one you're having a problem with.
Electricity is funny stuff, it will always find a way to complete the circuit if it possibly can, so when fault finding it's important to eliminate stray return paths.
In this case, we're looking at the lines connected to 2 terminals 'A4', the bottom Right and via the green link the Centre bottom.
The 3 wires on the lower Left are (hopefully) the unfused items and the feed to the fuse.

Start off with removing the fuse, unless it's still ruptured This is to ensure we don't get those pesky return paths we're not expecting.

Other than the green link, those cables are going off to the fused items on the switched live.
Undo those 2 screws and separate out the cables (remembering where you put the green link for later when you want to refit it )
Using the multimeter, set to Ohms, check each of those cables by having the black meter lead to the body metal work (or the earth on the battery) and then touching each of the individual lead ends with the red meter probe.
One of them is hopefully going to be well under 1 ohm. That's the problem one.

I can't be too specific because many Minors have had wiring changes made over the years, but for example it might be the trafficators. So when doing these 'resistance checks, you'll need to operate switches such as the horn, trafficators, interior light heater, blower rheostat, to see if they make a difference.
I suspect it may well turn out to be one of the trafficators, due to their electro-mechanical action.

I hope I've make that an easy enough description for you, any problems please come back and ask for clarification; it's easy for me to miss something that's 'obvious' to me with a lifelong electrical background.

That's an immense amount of help, thank you very much!

I did a bit more research and found a 1000 wiring diagram which gives me a bit more of an idea of what the bridge and black mess should look like and I've also since discovered my fuse box is missing a connection between the far bottom terminal and the lower right, which I presume is what the green wire is trying to replicate.

What I'll do is remove every wire and then connect an extra length of wire to each one, so we've got modern, clean wire for contacting with the fuses. That way I can also try and colour code somewhat, since all of the wires appear black or discoloured.

From that point, I can test as you've described and when putting the wires back in, the new cable should allow a bit more reach for fitment.

I'll let you know how I get on. But let's say it's the trafficators, how would I go about sorting the wiring on them? I fear it's a headliner removal job because if so, I may just have to bite the bullet and get light indicators to replace them for now, sadly

[jagnut66]

Hi,
If it helps the picture below is of my replacement loom, as it was, freshly installed into my 1954 Minor (Ignore the extra green wire linked in with the purple ones).
Following the wiring diagram in the workshop manual and matching it to my replacement loom, there was no wire going to the bottom connection, there is however a metal link connecting it (blue arrow), so I could have spread the whites wires out over the two.
Is your metal link missing?
I do appreciate that you have the same problem I had, in that all your wires are 'black' and that any colour coding on the outer cloth sheathing has been lost to the ravages of time.
I hope this is of some help and doesn't confuse things more.
Best wishes,
Mike.

New Wiring Loom 1 (2)_LI.jpg (1.32 MiB) Viewed 2206 times

[Andymoor94]

Hi,
If it helps the picture below is of my replacement loom, as it was, freshly installed into my 1954 Minor (Ignore the extra green wire linked in with the purple ones).
Following the wiring diagram in the workshop manual and matching it to my replacement loom, there was no wire going to the bottom connection, there is however a metal link connecting it (blue arrow), so I could have spread the whites wires out over the two.
Is your metal link missing?
I do appreciate that you have the same problem I had, in that all your wires are 'black' and that any colour coding on the outer cloth sheathing has been lost to the ravages of time.
I hope this is of some help and doesn't confuse things more.
Best wishes,
Mike.
New Wiring Loom 1 (2)_LI.jpg

Yes I found this through research. The green wire is replicating a missing brass line. A new loom would be a good idea, but I'm almost certain that getting into a job that big will likely take my daily driver off the road for a LONG time. That's gonna suck

[ManyMinors]

I didn't find replacing the loom to be as bad a job as I was expecting - and it is SO much better to be able to follow the colour coding. Fault finding is almost impossible with wiring that has lost its unique colours and frankly, if you're expecting to use the car reliably everyday, a couple of hundred pounds spent on a new loom will be money well spent

[Andymoor94]

I didn't find replacing the loom to be as bad a job as I was expecting - and it is SO much better to be able to follow the colour coding. Fault finding is almost impossible with wiring that has lost its unique colours and frankly, if you're expecting to use the car reliably everyday, a couple of hundred pounds spent on a new loom will be money well spent

I think given the tools and diagrams, I should come across too many problems. I could maybe do it in a weekend... what do you think?

[ManyMinors]

I think with a bit of planning and the right tools, you could do it over a weekend. Before you order a loom, think about any modifications you have or wish to fit in the future. These can be incorporated in the new loom which will be a much better job than adding wires afterwards

[Andymoor94]

I think with a bit of planning and the right tools, you could do it over a weekend. Before you order a loom, think about any modifications you have or wish to fit in the future. These can be incorporated in the new loom which will be a much better job than adding wires afterwards

Well apart from a clock on the dash, I'm not looking at adding anything, as far as I can think! No need for alternator, no requirement for flashing indicators (People notice my trafficators just well enough)... So I think the original should be fine... I'll have a think anyway!

Thanks for your help. No doubt I'll return shortly after a bit of testing

[myoldjalopy]

"But let's say it's the trafficators, how would I go about sorting the wiring on them? I fear it's a headliner removal job because if so, I may just have to bite the bullet and get light indicators to replace them for now, sadly"
I've never had to do this, so I don't know, but it should be possible to tie the end of a ball of string to the end of the wire at the trafficator end and pull the wire and string through from the other end. Leave the string showing at both ends and then you can pull back the original wire (if its OK) or a new wire, thus undisturbing the headlining. Check the trafficators aren't shorting out where the feed connects to activate them.

[geoberni]

I have no experience of the 4 door, so I can't comment on the trafficator access. My 2 door is easy.
I'd be wary of extending the cables, simply because you're adding yet another possible point of failure into the circuit. The only sure way of getting a good connection would be to solder each joint and sleeve or tape over it. Twisting the connections together is a recipe for disaster IMHO.
I'd find your problem first, and then consider a new loom based on that result.

Basil has a new loom (so looks much like Mike's photo), fitted by a previous owner, although he was also upgraded to separate indicators at the same time, but using a bastardised version of the 1961-63 arrangement.
Took me a while to understand what had occurred. Luckily the trafficators were still fitted but with no wiring to them, so I reinstated them with another bespoke modification. (See here viewtopic.php?f=11&t=72067&p=654490#p654490 )

So afraid I can't help with details of original trafficator circuitry.

I hate trying to decipher which wiring diagram is relevant in the manual, but I suspect your car may be the one on page N27 or N28. Your green wire is as you say, the replacement for the brass link, which is illustrated by the thick black line between the 2 A4 shown on the diagram. The fuses are illustrated by the thin diagonal line between A1-A2 and A3-A4.

Fuse Link.JPG (50.64 KiB) Viewed 2167 times