Put the negative lead of your Digital Volt-Ohmeter on the battery ground post (with meter set on DC Volts), then put the positive post anywhere you've a questionable ground. Power up and see how much voltage you read....should be very very small (less than .1). It may look good on a resistance check, be be no good under actual load. (NOTE: During starter cranking you could see .5 volt but not really have a big problem....depends on wire size and length)
To check a circuit under load, for example the wire to the coil + terminal, use this test.
1. Disconnect terminal wire and connect it to the probe end of your 12V test light.
2. Connect the clip of your test light to good ground or battery negative post.
3. With voltmeter on DC volts, put the negative DVOM probe on the battery positive post, and the positive DVOM probe at the test light probe (BEFORE the bulb).
4. Read the "voltage drop" on the voltmeter. Again, this should be very small. If it's reading more than a .1-.2, you have resistance in the circuit UNDER LOAD, even if your ohmeter says NO resistance. The ohmeter doesn't push enough amps through the circuit to identify corroded copper or broken strands.
Hope this helps....the salt sure tears up our wiring!
Regards, JimL