My car won't even turn over, no gauges work, my lights won't turn on. Bought and installed a brand new battery, still nothing changes. Just replaced starting relay, also. Any idea why my car won't start?
Do you have a digital voltmeter and know how to use it? If so, start right on the battery posts and measure the voltage. Move the probes to the battery cable clamps and measure again, then work your way down the cables to the next accessible points. You're looking for the first place you find the voltage missing. The tests will be more accurate if you turn on the head lights even though they don't work. In particular look where the smaller negative battery wire bolts to the body and the smaller positive wire bolts to the under-hood fuse box. Those connections often work loose.