Don't be soldering your automotive electrical connections

I've been meaning to write this article for years now and my recent VBOX install finally gave me the opportunity to do some crimping.

[Possible spam links removed by moderator]

I see, hear, and read about folks soldering their in-car electrical connections all the time and it's generally a bad idea. Crimping it the proper way. Solder just turns your ductile stranded core wire into what is effectively solid core wire (for the affected region), which is fine for homes but has no place in an automobile.

If done right, crimp connections can be very reliable, but the premise that the rigidity presented by soldering a connection versus crimping is flawed. A crimp connection is also rigid for the length of the crimp. And the fact is, very few folks want to buy the high end crimp tools to make reliable, production-style crimps. I would venture to bet that crimp style connections are common place in OEM automotive connectors more due to the speed at which crimps can be performed (reducing costs significantly) rather than due to the reliability. Similarly, the OEMs are using weather-tight connector housings for connections outside the cabin of the vehicle, but few folks would use such a connector when making a splice. I've seen the standard splices and tees used too frequently by "professional" trailer hitch installers to wire up trailer wiring. And very often these will lead to brake light failure of the tow vehicle and trailer due to permeation of salt water in to the splices. Had a solder splice been used and properly protected with adhesive-lined shrink sleeving, these joints would not have failed to provide protection from the elements.

A solder splice can be shorter than a crimp splice, and when properly insulated with adhesive-lined shrink sleeving, will also provide strain relief from vibration as well as protection from the elements. This type of splice can be made much more successfully by a less experienced individual, and with easier to acquire materials, than a proper environmental crimp splice.

-Rod

Unfortunately, moderator thinks my link to crimp DIY is spam so there's a lot of context lost. I'm not going to repeat full DIY and explanation here as it's far too long for a BB post and something I want to share within the forums I frequent so write / edit once, then link. Logical and reasonable.

My title "Don't be soldering your automotive electrical connections" is definitely a bold and general statement. Soldering can definitely be OK if done right, just as crimping can be worse if done incorrectly. Most people I've seen (and read about on forums, etc.) get it wrong just as I have in the past. Goal of the article is to get people thinking.

If interested in reading, go to digitalmee.net and seek out the "Making reliable electrical connections for your car" article.

Auto manufactures have a vested interest in ensuring reliable electrical connections. Crimping is both cheaper from manufacturing standpoint (as you point out) and more reliable which is to the benefit of their financial bottom line too. (Reputation for quality, cost to recall defect, etc.) Military and professional race teams (incl. F1) crimp and not solder as well. There are a variety of connector types available ranging in cost. A person can go with a connector (and associated tooling) that fits their budget. I use MilSpec stuff which is $$ but there are less expensive options that are still much better than soldering connections IMO.

You are correct that a connection pin is rigid too, but the pin part is contained within the housing so it is physically prevented from flexing and therefore ductility is not a significant factor. However, if the solder wicks past the connector pin and into part of the wire that would otherwise flex, you've now introduced rigidity where you don't want it and effectively turned your stranded core wire into solid core wire which has no place in a car. Sure, solid core wire bends but it has far less fatigue life than stranded core wire. Solid core wire is cheaper to manufacture too (which is why used in homes) but auto manufacturers don't use that to save cost because vibration and flex will eventually take their toll and cost then billions in recall costs down the road.

You are also correct that solder splices are OK (I've used them too). But they are designed to be foolproof. Just crimp and apply heat. I prefer barrel connectors and heat shrink. Much cheaper (for the cost conscious) and less bulky than solder splices.


-Roland.

The only wires I solder are the ones related to the computer and its sensors. These I then insert into GM Weatherpack fittings with a bit of dielectric grease on the pins.
Other wires, I just crimp and cover with heat shrink if possible.
You also have to route and support your wires in such a way that they don't flop around.
That's common sense.

Unfortunately, moderator thinks my link to crimp DIY is spam so there's a lot of context lost. I'm not going to repeat full DIY and explanation here as it's far too long for a BB post and something I want to share within the forums I frequent so write / edit once, then link. Logical and reasonable.

The links were removed because you had no post history and the post had links to an external site. Due to these concerns, the post was sent to the moderation queue (automated process). Not knowing if you would be an active member (or if you were just stopping by to generate traffic to an external site) and considering article had links to purchase the products discussed, the possible spam links were removed.

You are correct that a connection pin is rigid too, but the pin part is contained within the housing so it is physically prevented from flexing and therefore ductility is not a significant factor. However, if the solder wicks past the connector pin and into part of the wire that would otherwise flex, you've now introduced rigidity where you don't want it and effectively turned your stranded core wire into solid core wire which has no place in a car.

From the perspective of connector terminals and cable terminations (ring terminals for grounding, etc), I agree that a crimp connection, when done right, provides a great mechanical and electrical connection when inside the cabin of a vehicle. For general wire splices though or new connections underhood/under body , I'll stick with solder and adhesive-lined connections. Environmentally sealed connectors are just too expensive, rare (not readily available at the local parts store), and bulky for most jobs. And as mentioned above, when properly strain relieved and supported, I've never had issues with soldered connections failing, wires breaking, or corrosion setting in.

For a kit car, race car, or other application where several wires need to be connectorized, using a sealed connector with properly crimped terminals is the way to go in my book. But, either way, the connection needs to be performed correctly in order to be reliable. We use the Mil-spec circular, micro-D, and nano-D connectors regularly at work for high-dynamic applications and solder cup is an accepted approach, but for ease of assembly, crimp style is what's preferred by the technicians.

-Rod

I used to repair electrical systems on Apache helicopters in the Army. Every wiring repair was soldered. If a soldered connection will withstand the vibrations of a helicopter I am pretty sure they will survive in an automobile. The superior electrical connection of a soldered joint outweighs any alleged strength benefits of a crimped joint.

A customer of mine dragged around an auxillary backup light for miles by my soldered joint, I doubt many butt connections would have held as well.

I for one one will certainly continue to solder, even if it does take longer.

Here in the rust belt soldered connections are the norm for external wiring, due to the fact that salt eats the aluminum crimps in about 2 seasons. heat shrink will not seal out salt.