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Q: The car is not starting after I changed the aux cable in the stereo.

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After changing the stereo aux cable, the car is not starting. When I try to start the car, I hear loud cracking noise. Then, door lock doesn't work, some lights turn on automatically. The door lock works and the light turns off after I remove one of the terminal of the battery. If I just turn the keys on, after some seconds, the hazard light, headlight and dashboard lights starts blinking rapidly. After a while everything turns off. The same thing happens again if I turn of the engine and turn on again. I tried to find the short using multimeter. I disconnected the positive terminal and connected one end of the multimeter to positive terminal and another end to the removed positive wire of the battery. The short test showed 11.4 V. Then I removed fuses one at a time. But, the voltage reading remained same. Then, I removed all fuses and still test showed same voltage. Please provide me some suggestions. I am being totally helpless.
My car has a manual transmission.

To begin with, the lighting and door lock modules are very sensitive to low battery voltage. Once the battery voltage drops, they can start to do crazy things, making the car appear haunted. Door locks and windows may start to operate at random even while the car is parked. So, first you want to be sure the battery is fully charged. Second, you need to re-visit that stereo installation.

Check that all the connections are in accord with the factory system. The factory radio has a CAN (Control Area Network) line going to it. This is the line that all the modules use to communicate with each other. Since it tests at 12 Volts with a meter, many accessory installers mistakenly hook the CAN line up to an accessory radio. When this happens, the car can really exhibit some weird symptoms.

The CAN Line can be distinguished from the rest of the electrical system because it is a twisted pair of wires. It should not be hooked up to an aftermarket radio. Plugging the CAN line in where it should not be can damage one or more of the car’s control modules.

Beyond that, I suggest you get professional help. A certified mechanic, such as one from YourMechanic, can come to your location to inspect for electrical problems and suggest needed repairs.

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