You need more accuracy in those measurements. 12.2 volts indicates a battery is okay but discharged. A fully-charged battery will measure 12.6 volts. First find where the smaller positive battery wire bolts to the under-hood fuse box. Be sure that connection is clean and tight.
Next, measure the battery voltage again while a helper tries to crank the engine. Put the meter probes right on the posts of the battery, not the cable clamps. If the voltage drops a lot, suspect a bad battery. If the voltage stays up near 12.6 volts, move the meter probes to the cable clamps and measure again. If the voltage is lower there, one of those connections still has a problem.
You can do the same test at the fuse box connection. For this one, leave the meter's negative probe on the battery's negative post, but move the positive probe to the stud at the fuse box, not on the terminal that is bolted to it.
An alternate way of doing this test is to put one meter probe on that stud, and the other probe on the terminal. Logic says those two places are the same point, so they should have the same voltage and the meter will read 0 volts, the difference in the two places, but if you DO read a voltage there, that is proof there is not a good physical connection. This test is most accurate when current is trying to flow through the circuit. Turning on the head lights or heater fan will insure that happens, and it will make a bad connection easier to spot.
Thursday, January 22nd, 2015 AT 6:54 PM