Your car might be different than most others, but normally you should have a fat negative cable that bolts onto the engine or transmission, not the frame or body. A smaller negative battery wire bolts to the body. That's the return for the lights, fuel pump, and all the other electrical stuff on the body.
Sometimes imports use a single fat negative cable that goes straight to the engine, but along the way they tap in a crimped-on terminal that is bolted to the body.
If the cables are right, use a digital voltmeter to measure the voltage right on the battery posts. You must find 12.6 volts, which indicates the battery is good and fully-charged. If it's around 12.2 volts, charge it at a slow rate for an hour first. Measure the voltage again while a helper tries to crank the engine, (turns the ignition switch to "crank"). The voltage must stay above 9.6 volts. If it does, move the voltmeter's probes from the battery's posts to the cable clamps and repeat the measurement during cranking.
Now move the negative meter probe from the cable clamp to a paint-free point on the engine or transmission. Move the positive probe from the cable clamp to the large terminal on the starter solenoid where that cable is attached to. Do the measurement again.
What you're looking for is the first place where the voltage is considerably lower than in the previous test. That will indicate the point of the bad connection, if there is one.
If you still have more than 9.6 volts at the starter solenoid terminal, move the positive probe to the other large terminal on the solenoid. That one will have 0.0 volts at first, until the solenoid engages. If the solenoid is chattering during the attempted cranking, the voltage reading will not be valid or of any use. If the solenoid stays solidly engaged, THEN this second reading will have value. You should have very close to the same voltage on both large terminals during cranking. If the second one stays at 0.0 volts, or very low, there's worn contacts inside the solenoid. It's easiest to just replace the entire starter for that.
Monday, December 21st, 2015 AT 5:45 PM