Need Help....No Power

So I go over to the in laws house, put the key in and power is restored.
Turned the key and it fires right up with no problems?!
There was definitely something going on because there was a lot of fluctuation in the ammeter and the dome light would pulse
Since I had it started, we jumped in and drove it home.
Made it home with no issues and shut it off.
Checked the power and everything is working as normal: Headlights, dome light and open door buzzer
Turned the ley and it fired right up again....???
Can anyone give insight on the amp meter jumping around? I have all brand new wire harnesses under the hood. Ever since we got the car running the volt meter jumps around and dash lights pulse with it. Been trying to figure that out. Now today went to start, no dice. Nothing at the key, will turn over jumping relay but with key on won't start. Noticed the fusible link if cooked. I'm assuming it probably has something to do with the jumping volts . Please help.