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Q: Sometimes will not start.

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Sometimes will not start. You turn the key and nothing. I changed the starter and the ignition switch and still sometimes will not turn over.

My car has 40000 miles.
My car has an automatic transmission.

A: With intermittent no crank conditions, you ...

With intermittent no crank conditions, you most likely have a bad connection in the primary starting circuit. This is the battery, the positive and negative battery cables and the starter. Even though you have replaced the starter, new or remanufactured starters can be bad. In this case, I would suspect a bad connection in the positive or negative cables. Keep in mind, just because a wire is touching, it does not mean it is a good connection to electricity. The connection must be tight and clean. If there is corrosion, both surface and other, it will make it difficult for electrical current to flow. The most accurate way to test for bad connections in an electrical circuit is to do a voltage drop test. A voltage drop test is not something I can explain here. It needs to be demonstrated to be understood. The next method is to disable the ignition system and crank the motor for about thirty seconds then feel the positive and negative cable connection for heat. A high resistance connection will get hot to the touch. If this works, disassemble the connection and clean it with sand paper.

High resistance can occur in any part of the primary and secondary starting system. If you car so inclined, you can use a test light to find where the power stops when the car won’t crank. This requires a wiring diagram, careful study of the diagram and a test light. Testing in this way will need to be done when the failure is occurring.

If you need help, I recommend getting your car looked at by a qualified technician who can diagnose your starting issue. Keep in mind, the only way to diagnose this is if the failure is consistent. If a technician shows up but the car is starting normally, there is no way of being sure what is wrong. Our mechanic maybe able to make some recommendations based on what he sees, but that is up to the mechanics discretion.

Good luck!

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