| 1) The best connection is a properly done solder joint. | | | | headlights, parking lights, horns, etc., with low |
| If you aren't sure how to solder, crimp the | | | | amperage outputs such as those found on keyless |
| connection then solder it. Cold solder joints not only | | | | entry and alarm systems, and other components. In |
| introduce resistance, but they can come apart. | | | | some cases you may need to switch multiple things |
| 2) Keep your grounds as short as possible. It is far | | | | at the same time using one output. A single output |
| better to have a few more connections than a long | | | | connected to multiple relays will allow you to open |
| ground that can build heat and introduce ground | | | | continuity and/or close continuity simultaneously on |
| loops. It is common practice to run a ground wire | | | | multiple wires. |
| from a high demand devise such as a fuel pump back | | | | 7) Most electromechanical devises are rated |
| to the battery. This not only adds additional loads to | | | | according to the MTBF (Mean Time Between |
| the pump or devise but also can lead to device | | | | Failures). You improve your odds of a long MTBF by |
| failure. Have you ever seen a production auto with a | | | | keeping your electrical devices in a low humidity, low |
| ground cable longer than the positive cable? | | | | heat environment. |
| 3) If at all possible, use stainless hardware to fasten | | | | 8) Do not ever use THHN/THWN wire. This wire |
| all primary cables. Some galvanic or plated hardware | | | | (insulation) classification is not rated for automotive |
| can cause dissimilar corrosion and can sometimes | | | | use. Cars move and vibrate which chafes the |
| carry more impedance that its stainless counter parts. | | | | insulating material. |
| On smaller secondary circuits, this is not as important. | | | | 9) A wire that is rated for A/C voltage may have a |
| 4) Battery storage. Keep batteries away from | | | | different rating when used in low voltage D/C |
| humidity. Keeping it charged will prolong its life. If a | | | | applications. Your house uses A/C, your car uses D/C. |
| battery is dead, cool it before you charge it. Put in | | | | 10) The best primary power cable is a type TEW or |
| the refrigerator or outside if its cold. Cool batteries | | | | MTW (Machine Tool Wire) as its rated for continuous |
| charge better. | | | | use with higher amperage loads. |
| 5) Batteries specifications and charge rates are for | | | | 11) OFC (oxygen free copper) is by far the best |
| 77 degrees Fahrenheit. Temperature variations will | | | | cable for automotive use. However, it is expensive |
| change charge rates. | | | | and requires a quality crimper and should be soldered |
| 6) Use relays. Anytime you want to switch a device | | | | for security. The most common application for this |
| that draws more current than is provided by an | | | | wire is high-end car stereo applications. |
| output of a switch or component you'll need to use a | | | | 12) If you are like me, you may choose to skip OFC |
| relay. The coil of an SPDT relay that we most | | | | and go with TXL wire. TXL (thermal cross-linked) |
| commonly use draws very little current (less than | | | | wire is next best. TXL wire has twice the voltage |
| 200 milliamps) and the amount of current that you | | | | rating of standard GPT (general purpose) wire. Most |
| can pass through a relay's common, normally closed, | | | | high-end harnesses are made with this wire. If you |
| and normally open contacts will handle up to 30 or 40 | | | | want to keep your ride for the long haul, you may |
| amps. This allows you to switch devices such as | | | | want to pony up for a harness made with this wire. |