What solder to use on basic automotive wiring?

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dibbons said:
I would like to do some wire repairs using soldered connections instead of the crimp connections that (for me) often fall out no matter how hard I crimp. What is the best type/mix/ratio solder? My past experience soldering wires were not much better than the failed crimps.
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Lets break this up. Crimping requires the correct size connector for the wire. The connectors are usually stamped with the wire size. A magnifying lens may needed. Some with insulators are also color coded. Decent crimper helps too and has already been discussed.

A potential disadvantage of soldering is overheating or oversoldering. For this reason a lower melting point solder is generally advantage for electrical and electronic work. Advantage of soldering is a strong joint that moisture can't attack. Bill Grissom's description is good. I'll add a few things FWIW.
I personally like a 25 or 40 watt pencil size soldering iron when working on the car. The radio shack ones are decent for how cheap they are.
The wire must be clean! The metal from both wires or wire and connector must be in good contact with each other. Use a bit of non-corrosive rosin flux. If you're using a flux core solder wire, the flux will melt out first. I think its harder to control but most people seem to prefer flux core.

Alloys: 63/37 or 60/40 are both good for electrical work. Lower flow temperatures mean the least heat transferred to insulation etc.

63/37 is the lowest melting point AND it goes from solid to liquid with no transition. People doing circuit boards and wiring to or near electric motors often will choose this.
All other solder alloys have a temperature range where it is semi-liquid. They needs to get to the full liquid state to flow properly into the wire joint.

60/40 is also used for electric work but it becomes fully liquid at a higher temperature than 63/37.

Wire is spec'd by alloy, wire diameter, how much flux in the wire, and type of flux. Don't let this get you flumexed. For automotive electrical I find a smaller wire diameter is easier to use. Fluxes have a couple different standardized designation systems plus manufacturers description. Just ask the seller if you're not sure.
Approximate melting points from
McMaster-Carr
Sn/Pb Melting Temp (F)
63/37 360
60/40 375
50/50 420
40/60 460

A bunch of information on Kester's website including the http://www.kester.com/knowledge-base/
 
KitCarlson said:
Because they know what they are talking about.
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if every wire wasn't solderd in a fishing boat with in one year it would not be safe to go to sea in . so please tell my why non solderd wire connections are a better way to go .
 
Agree its interesting point of view, but as the anonymous poster states in the begining, its his opinon and the rest was his reasoning for his preference. One point of contradiction is about the connection - a crimp first will not prevent solder from flowing up the strands unless the copper strands have been completely deformed.

The extra stiffness is a legit concern. So if/when a soldered connection is made, its important not to overheat because the solder will flow to the heat (unless its too hot). Regadless of soldered or crimped, with any electric or plumbing connection, its always good practice to make sure there is both strain relief and support. Many many electrical connections are soldered: The diodes in our older alternators are soldered. When they fail its not the connection, its the diode :lol: The connections inmy family's 1930's Singer sewing machine are soldered - the wire insulation is shot (and that's why I know this, since its on my fix list for next week) but the connections are just fine. Did you know the proper way to add on to knob and tube wiring requires soldering? Of course there's only limited situations where anyone needs or wants to do that these days, but its still allowable in the code (NEC). Thats good for 110 to 115 V and 15 amps in most cases.
 
I read the marine articles and have read other info in the past. Soldering after crimping has 2 advantages - backup in case your crimp wasn't tight and corrosion protection. Circuit board copper traces are usually "tinned" w/ solder to prevent corrosion, as is some stranded copper wire during manufacture. If a crimp is very tight and perfect, it can be "oxygen free", thus the interface between the copper won't corrode (turn green, copper oxide). I know the "fused" (welded?) ALT wire junction under my dash wasn't tight enough because mine was green in both A's, and many have found those melted from corrosion. The main downside of solder is it stiffens the wire so it may not flex enough and break, if in a place were it gets tugged.
 
Let's keep in mind at the modern solution to keeping the crimped connections from corroding: sealing the crimps reasonably well from moisture. This is done nowadays in cars by good seals around connectors that are exposed to moisture, both for the contact and the crimp. You can do this in car wiring by using some 'flooded' heat shrink tubing over the crimps, and avoid the problems of work hardened, solder-wicked wires breaking off.

If you do solder, then just be sure to support the wires a few inches away from the solder joint. A boat would be included; the pounding and shaking in rough waters is pretty major. Like I said, I stopped soldering in my race cars: those are rally cars that take constant pounding and shaking and vibration. You learn pretty quickly what does not work in that environment!
 
I usually crimp and solder if I have to use a connector. Otherwise I solder wires directly together and use shrink wrap.
 
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