I am working on my engine harness replacing some wires that are brittle and losing some insulation. While I am working on it, I found 3 to 4 crimp joints (from the factory) so I am wondering whether I should pull them apart and replace them with solder connections? How reliable are those old crimps (92 camaro) from the factory?

 

Generally speaking properly crimped wires hold well. As long as they are not strained or visibly corroded.

soldering is good, however the wire at the solder connection tends to get e little brittle. I would not recommend soldering factory crimped connections. On new work, I sometimes allow the copper to go into the crimp terminal and extend on to the terminal just a bit. Then carefully solder the protruding wire to the metal terminal.

I don’t do that very often

 

The complicating factor is that there are multiple wires crimped in a butt connection fashion.

 

Solder and or crimp with good heat-shrink tubing, and you should be good. Better off than a forest of butt connectors, I would think. You can also stagger the joints to help prevent the unavoidable harness bulge from splicing.

 

FWIW, I have always repaired / lengthened wiring by soldering and then heat-shrinking the connections since forever (60+ years) and have never had a come-back or repeat problem with any such repair. I have to add thought that such repairs require good soldering practice; sloppy work / cold solder joints are to be avoided.

 

If you're talking about the ones such as, for example, where the pink/blk from the fuse block gets split out to all the different devices that are hooked to that circuit, then the factory's splices are generally fairly reliable. Butt if you're worried about them for some reason, you can just leave them alone and solder them as they already are, using plenty of heat and LOTS of rosin flux such as https://www.microcenter.com/product/...soldering-flux or https://www.digikey.com/en/products/...RA891/12352196 followed by electrical tape. If you're having to replace any of those particular wires, you can cut the originals out, use an uninsulated butt splice of whatever size is big enough to accommodate all of them, and solder after crimping.

 

I think you're describing a splice for power distribution or grounds? I would leave it alone unless something is damaged or corroded. Those factory multi-wire splices are better than what you can do at home.

 

When you have had to salvage or repair enough OEM Harnesses...

You quickly learn that while adequate when new; the OEM Power Distribution Splices are unsealed and the mating Conductors are often horribly corroded.

 

For Power Distribution Circuits, an unsealed Parallel Splice would be ideal over a Butt Splice.

The Parallel Splice allows all Conductor Strands to make contact with one another directly.
The Butt Splice, however does not allow for Conductor to Conductor contact and the Splice itself is responsible for the contact between Wire Segments.

Anytime the demand for Current is a factor, Butt Splicing should be avoided as there will be unnecessary heat, resistance, and Voltage drop.

Unsealed Splices should ideally be sealed off via Epoxy Lined Heat Shrink Tubing or other similar appropriate sealing methods per application demands.

 

I defer to vorteciroc's recommendation.

 

You can take a butt splice and jam all the wires into one side of it and make it the same as a "parallel" splice. (which the factory never did; their spliced wires usually go both ways from the splice) You can even cut off the unused end if you do that. There's no rule that says you can't. For that matter, you can even cut it in half FIRST, and jam wires into it from both directions, if need be.

IOW, just use the butt splice as a "raw material", not a "part".

 

In regard to Parallel vs. Butt Splicing techniques...

The orientation/ direction of the Wires inserted into the Splice is not really of any concern...

A Parallel Splice can have all the Wire Segments placed in the same direction or opposing directions...

What is truly important is that all the Wire Conductors are on top of one another in the Splice, and not Butted together.