3 Wires, 1 Crimp Connector

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
Hi, I’m just wondering what people’s opinions are of crimping three wires into one connector as I’m not sure if this would be a safe/ok way of doing what I want to do.
For context, I’m converting the standard fuse box (4 way, 8 connectors each side, glass fuses) in a classic mini to a 4 way, 4 connectors each side, blade fuse box. Pictures attached show how the original wiring has 2 wires in one crimp and 1 wire in its own connector. TLDR: Sorry for the waffle, basically would it be ok to crimp these three wires (green/orange) into one connector.5DDD69D1-B233-431B-98ED-A7F0897FF33C.jpeg
Converting from this:0F0400C5-0063-42E4-AB10-FB88E51426B2.jpegTo this:
1904FC49-FBAA-4064-B02B-5C1C3667EDA2.jpeg
(EDIT: Sorry just realised I could of posted this in automotive electronics, maybe an admin could move it? Thanks)
 
Last edited:

dl324

Joined Mar 30, 2015
9,332
I've seen people crimp two wires in a connector intended for one, but 3 is probably out of the question for reliability. Crimp on connectors typically have some strain relief for the wire. That won't work for more than one wire.
 

jpanhalt

Joined Jan 18, 2008
8,340
1) Strain relief is important.
2) Is this what you mean by piggy back?
1573642643893.png

If so, I don't see a problem with it.
3) Be sure you don't exceed the wire gage capacitoy of the connector. Some will actually come with that specification, e.g., 2x18 .
 

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
1) Strain relief is important.
2) Is this what you mean by piggy back?
View attachment 191331

If so, I don't see a problem with it.
3) Be sure you don't exceed the wire gage capacitoy of the connector. Some will actually come with that specification, e.g., 2x18 .
Yeah that’s what I meant by piggyback. Thanks for your help. In two minds whether to just stay with the standard glass fuse box. Simple, works and not over complicating things. Plus I need blade fuses half the rating of the original glass fuses. Which means finding a 17.5 amp and 12.5 amp, if they even exist!
Cheers
 
Last edited:

bwilliams60

Joined Nov 18, 2012
1,233
The proper way to do this for automotive would be to splice the three wires together and run a single wire to the terminal. The terminal and the single wire would have to be large enough to carry the amperage of all 3 wires together. The fuse block would also have to be rated for that amperage as well. Splicing is very common in automotive dashes.
 

Freq

Joined Oct 25, 2019
4
bwilliams60 nailed it. splicing would be the most reliable way to terminate all 3 wires into 1 terminal. Personally, I would solder splice the wires together into 1 larger awg wire that is suitable for the current needed, then add some heatshrink over the splice area. You can also find crimp splices or even heatshrink splices that could work but you need to be careful putting 3 wires in either of those to insure a good connection.
 

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
The proper way to do this for automotive would be to splice the three wires together and run a single wire to the terminal. The terminal and the single wire would have to be large enough to carry the amperage of all 3 wires together. The fuse block would also have to be rated for that amperage as well. Splicing is very common in automotive dashes.
Yeah this was the other way that I was planning on doing it. Thanks for that explanation of it aswell. Confirms what I was thinking, thanks aswell to Freq.
Because the original glass tube fuses are 35, 25, 25, 15. My understanding is that is the continuous rating is half the actual rated blow. EG 17.5A continous, 35A blow. Continuous is what a blade fuse is measured in. Therefore needing 17.5 amp blade fuse. Of course I could go down to 15 or up to 20 but trying to get as accurate spec as possible.
 

Tonyr1084

Joined Sep 24, 2015
3,941
Because the original glass tube fuses are 35, 25, 25, 15. My understanding is that is the continuous rating is half the actual rated blow. EG 17.5A continous, 35A blow. Continuous is what a blade fuse is measured in. Therefore needing 17.5 amp blade fuse. Of course I could go down to 15 or up to 20 but trying to get as accurate spec as possible.
Interesting. I never considered that aspect of fuses. Goes to show that old dogs DO learn new tricks.
 

Reloadron

Joined Jan 15, 2015
4,722
Yeah this was the other way that I was planning on doing it. Thanks for that explanation of it aswell. Confirms what I was thinking, thanks aswell to Freq.

Because the original glass tube fuses are 35, 25, 25, 15. My understanding is that is the continuous rating is half the actual rated blow. EG 17.5A continous, 35A blow. Continuous is what a blade fuse is measured in. Therefore needing 17.5 amp blade fuse. Of course I could go down to 15 or up to 20 but trying to get as accurate spec as possible.
I would not count on that. Glass tube fuses like you are replacing come in several flavors but the two popular names are fast-blow and slo-blow. Glass fuses used in automotive applications can be either and if you look at the fuses carefully the end caps will have the current rating and the type. For example these fuses are rated for 32v DC and cover from 4 amps up to 30 and may be labeled SFE and AG* (* could be any of several letter codes like AGC) type fuses are fast-blow fuses, they pop as soon as there is more draw than they are rated for. MDL for example is a slow-blow type fuse and the only difference is a delay on slo-blow fuses. The Littlefuse link I provided earlier shows Time / Current characteristics. Anyway it is the designations on a tubular glass fuse which determine what it should be replaced with. Replace your existing fuses with blade type automotive fuses having the same current ratings. That would be my advice anyway. Using a fuse rated for half the current of the original fuse will result in replacing a lot of fuses.

In automotive older glass tube types about the only application I can think of that used a slow-blow or MDL type fuse was the fuse for the heater A/C blower where on start the blower motor would draw a high start current for a split second.

Ron
 

SteveSh

Joined Nov 5, 2019
104
I was wondering also why Minimayfair wants to reduce the rating of the fuse by half from what is in there originally. Fuses and other circuit protection are usually there to protect the wiring, but have sufficient current carrying capability that there are not nuisance blows. If Minimayfair is going with smaller gauge wire to his loads, then a reduction in fuse size may be warranted.

Minimayfair - is this new fuse block something your adding to provide power to new loads, or is it replacing a existing fuse block?

The 50% derating Minimayfair mentioned - using a 30 amp fuse to protect a 15 amp (max) load for example, is reasonable.
 

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
I was wondering also why Minimayfair wants to reduce the rating of the fuse by half from what is in there originally. Fuses and other circuit protection are usually there to protect the wiring, but have sufficient current carrying capability that there are not nuisance blows. If Minimayfair is going with smaller gauge wire to his loads, then a reduction in fuse size may be warranted.

Minimayfair - is this new fuse block something your adding to provide power to new loads, or is it replacing a existing fuse block?

The 50% derating Minimayfair mentioned - using a 30 amp fuse to protect a 15 amp (max) load for example, is reasonable.
It will be replacing the existing glass tube fuses to convert to blade type fuses. Lucas glass fuses are rated by the current which would blow them very quickly, whereas all other fuses everywhere, as far as I am aware, are rated by their continuous current carrying capability. The wiring will be the same. Most of my information has been taken from theminiforum. The other way I’ve looked into splitting circuits rather than crimping all together is pictured. Effectively using a daisy chain on the input side and individual wires on the output. This makes it so each circuit is fused separately for easy diagnosis I think. 5105146D-1CD8-4D65-80F5-04E9B1440C30.jpeg939E486D-4133-468B-B778-470FE092229F.jpeg
 

jpanhalt

Joined Jan 18, 2008
8,340
It will be replacing the existing glass tube fuses to convert to blade type fuses. Lucas glass fuses are rated by the current which would blow them very quickly, whereas all other fuses everywhere, as far as I am aware, are rated by their continuous current carrying capability. The wiring will be the same. Most of my information has been taken from theminiforum. The other way I’ve looked into splitting circuits rather than crimping all together is pictured. Effectively using a daisy chain on the input side and individual wires on the output. This makes it so each circuit is fused separately for easy diagnosis I think.


That is why I prefer the piggyback connector. Yes, I have put two wires into a single connector. As that number increases, the likelihood you will need to isolate one circuit from the others increases. The piggy back connector does that for as many circuits as you want to use.
 

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
That is why I prefer the piggyback connector. Yes, I have put two wires into a single connector. As that number increases, the likelihood you will need to isolate one circuit from the others increases. The piggy back connector does that for as many circuits as you want to use.
Yeah very good point actually. However in the event I wanted to isolate one of the circuits, for example white wire on the 8 fuse box diagram, I could just unplug the connector from contact 2 on the fuse box which would leave contact 1 circuit connected would it not. Also I would think 3 piggybacks could get quite bulky whereas this keeps it against the bulkhead and more compact and crimping two wires as shown looks pretty good and secure to me. 1B387453-4A81-48FE-8024-33763203085B.jpeg
 

jpanhalt

Joined Jan 18, 2008
8,340
You show two red wires. Are they for the same or different circuits? If same, why two wires instead of a single larger one? That's what I was referring to. One thing that really bugs me to no end are so-called "mechanics" who slice into a wire's insulation to connect to that wire. I have never done that and never will. Thus, piggy backs or other means to isolate a circuit (like knife connects) are what I use.
 

Thread Starter

Minimayfair

Joined Nov 12, 2019
12
You show two red wires. Are they for the same or different circuits? If same, why two wires instead of a single larger one? That's what I was referring to. One thing that really bugs me to no end are so-called "mechanics" who slice into a wire's insulation to connect to that wire. I have never done that and never will. Thus, piggy backs or other means to isolate a circuit (like knife connects) are what I use.
Sorry should of clarified. Them two red wires are nothing to with what we’re on about in terms of the fuse box. Just showing two wires in one crimp which I would have to do to make the daisy chain connection. Why not one wire? Because I’d like to have the fuses separate for each circuit, if I put it into one wire then this wouldn’t be the case. My original question has now changed I suppose to, two wires in one connector which I think is fine and is the 8 fuse fuse box design that I’ve done going to be safe and work correctly. As for knife connectors, hopefully you don’t mean scotch blocks as they are dreadful and should be banned! Nothing wrong with cutting insulation to splice into a wire as long as the splice is strong, soldered and re wrapped properly in my opinion but let’s not open another can of worms!
 

jpanhalt

Joined Jan 18, 2008
8,340
Hey, step back for a second and think about serviceability. Personally, I don't care what you do. Three wires in a suitably rated terminal is fine. But, it may not be the best solution.
 
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