When i turn on my directional blinkers on my mitsubishi 3000gt SL my battery gauge jumps. Why is this?

When i turn on the blinkers the battery gauge jumps up, and down. Sometimes the car shuts off during shifting to reverse. I bought a new battery already. I replaced the engine. I changed the transmission (automatic). Is this a serious problem, or is it just a bad wiring problem? Please help me. this is very... show more When i turn on the blinkers the battery gauge jumps up, and down. Sometimes the car shuts off during shifting to reverse. I bought a new battery already. I replaced the engine. I changed the transmission (automatic). Is this a serious problem, or is it just a bad wiring problem? Please help me. this is very important to me.
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