Electrical - Wire Crimps
I work at a technical institute and popped into the electronics shop to ask a few questions about wire crimping. Instead I received an eye opening lesson on wire crimps, wire crimp tools and crimping. So here's the info passed on to you guys:
There are basically three types of wire crimps used on vehicles: quick disconnect, ring and spade lug.
Quick disconnect connectors: 1/4" female on left and male on right
They are made to be pushed on and pulled off quickly.
Ring connector
The ring connector is made to be mounted on a stud (screw)
Spade connector
The spade connector is made to be slipped onto a terminal block's stud
The crimp connectors shown above are called insulated as the wire crimp part is insulated. You can purchase fully insulated connectors that insulate the connection too.
1/4" quick disconnect fully insulated connectors: female on left, male on right
My preference is for quick disconnect and ring connectors. A good quick disconnect connection will be very difficult to pull apart. I like the ring connectors for use on studs cause they can't fall off if the nut or screw holding them on loosens. If the nut or screw holding a spade connector on loosens, the connector may slip off and you have a live electrical connection sparking under the dash. Also, I have found that many times the spade connectors forks will spread apart while tightening and the spade connector will actually slip out from under the screw or nut supposedly holding it down - very frustrating if you are trying to work under the confined space of the dash.
Wire Gauges
The crimp connectors are color coded to indicate the wire gauge that they are made for:
- Red - 16 to 22 gauge wire
- Blue - 14 to 16 gauge wire
- Yellow - 10 to 12 gauge wire
In a car, stranded wire should be used exclusively. Stranded wire is made of many strands of fine wire that can be repeatedly moved without breaking from the vibration and flexing from driving. Solid core wire will break from vibration and movement. Solid core wire is typically used in your house wiring where the wires are stapled to the beams to prevent movement.
Sizes of connector fittings
In addition to the wire gauge, quick disconnect connectors come in 2 common sizes: 1/4" wide and 3/16" wide. The standard for automotive applications is the 1/4" wide version. Ring and spade lugs are made for a specific size stud and will have a number that corresponds to stud size: 4, 6, 8, 10, 1/4", 5/16", 3/8" or 1/2". The larger the stud size, the more current that the connector can handle.
A yellow ring connector with a stud size of 10 indicates that it can be used for number 10 to 12 gauge wire with a #10 screw stud. By the way, screws get physically larger with an increase in number size, while wires become smaller with an increase in gauge. An 8 gauge wire is a thick wire that would be a battery cable. A 30 gauge wire is as fine as a human hair.
Strain Relief
Best strain relief crimp has metal crimp sleeve right to the edge
The above picture shows the wire side view of two "identical" ring connectors. The difference is that the one highlighted has the metal crimp sleeve going right to the edge of the insulator. This is important as this style crimps the wire for a strong electrical connection and the wire insulation for a strong strain relief.
The non highlighted ring connector has only the crimped wire for strain relief and the wire will break eventually from wire movement and vibration. The highlighted ring connector uses the wire insulation as strain relief and will last a much longer time before failing. The difference in price is about 10% more for the good strain relief version. Unfortunately, not many electrical supply house partsmen know the difference, even those with lots of experience.
I've talked to several individuals that used non insulated crimps and then put heatshrink over the wire and connector for strain relief. It's more work and money and the result is not really worth the effort compared to using the right crimp.
Crimp Tools
Two types of crimpers: Red handle is a ratchet style, yellow handle is cheap pliers style
There are two basic types of crimp tools or crimpers: the ratchet style and the cheap pliers style. The preferred crimper is the ratchet style as it provides the ideal preset tension to the crimp. The pliers style is squeezed by guess and by golly. You hope that you haven't applied too much pressure cause you'll break or weaken the connector. If you don't apply enough pressure, the wire will be loose and not make a good electrical contact and may even slip out.
The cost for a ratchet style crimper starts at around $50 for a low end model and over $200 for a professional model. The professional model has removable dies for specific models of crimps. The dies cost $50 each.
I've purchased a commonly available unit: the Mode Electronics Model HT-301 for just under $50 and it will do red, blue and yellow electrical crimps. Unfortunately, I don't believe that it will crimp the insulation. For the insulation strain relief, I will use the pliers style to crimp that portion. The alternative is to purchase the $200 ratchet and I can't justify it for the number of crimps that I will be doing.