Have you checked yours lately? These seem to be becoming more of a problem. When I redid mine, I found the wires to have multiple broken strands at the solder to wire connection. As more strands are broken, the current carrying capacity of the wire is degraded. Below is something I copied from a forum on solder/crimp connections.
Almost any soldered joint will last forever if there's no vibration - that's the key. The solder itself isn't what fails, it's the interface point between the copper wire and solder, that's where the wires - not the solder - fail.
How true and this is just what I found on mine. If yours are OK, a way to help prevent the breakage of the strands is to immobilize the 4 wire harness with a sticky pad and a nylon tie as close to the connection as possible. Two, one above the other would be even better. This would keep vibration and movement to a minimum. I think most of our cars used to have a small piece of thin sheet metal welded to the left rear side of the battery tray just for this purpose, however, most are long gone. From the pics of engine bays I have looked at, almost none were being used and the harness was hanging loose, allowing vibration and movement that stresses the soldered connection.
If your 4 wire harness is long enough, you could do what I did in the pic attached. If you decide to do this, check how much movement you get by shaking the harness below the tie point and see how much less movement you get at the soldered connection.
Tom

Along those lines; years ago when I built my plane I was lucky enough to be around a couple of EE's that pointed out to me the importance of crimping the plastic sheathing around the crimp connectors. Look on your crimping tool and you will notice that one is marked "ins". This is the one to use on the plastic. It gives additional support to the wire/crimp/solder junction.

Yep. The non insulated crimp spot on the tool will cut thru the insulated crimp connectors. I crimp the connector just enough to hold it in place, then solder.

The type of crimpers that 76-914 is talking about make a VERY good crimp, however, I doubt any of us would pay the price. We used them in the shipyard and if you lost yours, it was over $250.00
Crimped connectors are better if the proper crimpers are used by someone who has learned how to do them. Most of us can do a solder and get just as good of results and they will last if you isolate the vibration.
This thread is not about crimp versus solder. It is about why our aging electrical systems can give us problems. Everything in the dash area and the engine bay, except the starter motor, gets it's power from these 4 wires. If you are having any wierd electrical issues, it would be a good idea to check the condition of these at the connector that bolts to the battery + terminal.
Tom

Over the last month, I have read several threads where folks were having electrical issues and traced them back to these 4 wires at the battery positive. Just thought I would bring this thread back up as a reminder for you guys to check yours out.
Tom

A crimp terminal gets two crimps. The first is for the connection and the second the insulation only which is a strain relief. If the terminal has been crimped properly, you should be able to pull on it and the failure will be in the wire and not the connection. That is why mechanics like to use the uber expensive ratchet tools and not the 2 dollar crimpers.

All terminal crimps do not get two crimps. A lot of the non insulated terminals get only one. This thread is not about crimping versus solder, however, It is about the 4 red wires, or three on early cars, and how they degrate over time due to vibration.
I did an autopsy on my wires there at the battery some time back when I replaced my connectors and added the fuse block.
On one of the 4.0mm wires, I had about 19 of the 55 strands broken at the solder connection. So I was in effect losing 1/3 or more of the current carrying capability on that wire. Factory connectors are soldered there. On one of the 2.5mm wires I thing half were broken. Seeing as how the youngest of our cars is 36+ years old, it would be a good idea for those wires to be closely checked, especially if you are having wierd electrical issues.
Tom