Electrical basics
Do's/Don'ts:
Do's:
1. Insure all grounds are GOOD. Check that good metal-to-metal contact is made. Scrape/sand paint/corrosion (rust) from chassis under the ground connection. "Star" washers also work OK, they tend to cut through the paint/corrsion, but only when the washer is new (don't reuse).
2. Use good quality crimp connections with good quality crimp tools.
3. Test all crimp connections by attempting to pull apart...if you can move the wire within the crimp, the connection is not good, crimp it again. If you pull the wire out, use a fresh connector and crimp it properly.
4. Solder all splices if possible. If it can't be soldered, use a good quality "butt splice" with a good crimp tool.
5. Seal all connections. I prefer a good electrical grade of RTV (I use GE RTV163) to seal crimp connectors. The best seal is heat-shrink with interior glue. Second is plain heat-shrink with RTV, last is electrical tape. Problem with electrical tape is that the adhesive "lets go" at temps normally under the hood.
6. Use a trouble light/METER for finding "hot" wires and diagnosing problems.
Don'ts:
1. Use the "twist and tape" method of splice. Exception here is of course the "get home" fix. But don't forget to fix it RIGHT at the earliest opportunity.
2. Use the "does it spark" method for finding "hot" wires. This will pop a fuse (wasted money) and possibly damage components.
3. DON'T EVER cut away insulation to test a wire, use a sharp probe, or find a "sewing pin" to clip onto and poke into the insulation.
General information:
1. Best tool for troubleshooting electrical problems is a multimeter. These vary in capability and price. My suggestion is to buy the best you can afford-but more expensive is not always better. For basic automotive use, you will mostly use the DC and continuity (ohms) settings. Look for sturdy SHARP probes (for poking through wire insulation, or one with good "alligator clips" and keep several of the wife's sewing pins handy.
2. Another good tool is a simple trouble-light. Looks like a clear-handled screwdriver, but has a sharp point at the business end and a wire coming from the handle that has a clip on the end. A light in the handle glows when the clip is attached to a ground and the sharp tip is on 12 volts. It's good for finding "hot" wires. Also good for finding "dead" cylinders on an engine that is missing. Just connect the clip to ground, and poke the sharp end through the spark plug boot to a spark plug tip. If you poke a spark plug, and it starts missing worse, that plug was hitting. If you poke one and no change, that plug was missing.
Added as suggested by fletch (Thanks

):
"another tip that could be added - i've solder pins to my multimeter leads. gets through the wiring insulation easily - good big thick sharp pins. "