Replacing welded splices on dash harness

If one did need to be fixed, what's the best method?

Pretty sure the splice on my harness where the blue ignition wire splits and goes up to the gauges or out to the ballast resistor is bad. I can't get power to the oil pressure idiot light and at one point the car wouldn't start and had no power under the hood. Going to dig into it when I pull the dash for my Rallye gauge swap.