My car won't start. We've changed the starter and tried many batteries. When we turn the key the volts on the battery drop from 12 to 7 or 8.
My car has an automatic transmission.
If the battery starts out at 12 volts and is dropping to 7 or 8 volts, then you have a bad battery. When cranking, it shouldn't fall below 9.6 volts. There may be other issues at hand, but the numbers you listed are that of a battery that needs to be replaced. Without knowing what signs are associated with the vehicle not starting, it's hard to say if there is a starter problem, a fuel pump that isn't supplying enough fuel, or an ignition problem. If the car cranks normally and just doesn't start, then I would look at the fuel supply, or check to see if the engine is getting spark. If you turn the key and just get a clicking sound, then I would suspect the battery (though until you have a battery that doesn't fall below 9.6 volts when the engine is cranked, the other tests will need to be questioned), a wiring problem, a faulty relay, or any number of other possible problems. It would be a good idea to have a certified technician, such as one from YourMechanic, diagnose your starting problem for you.
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