electrical problems in 1969-70 Technical Forum Posted 18 hours ago · Report reply Yes 257 should have power. Yes connect to 257 and the other end to chassis- should be around 12vdc. Edit: with the key in Accy or ON As previously stated, fuse 3 will be 30A with AC or 14A if heater only. If you don't have power on 257 (with key on), check both sides of fuse 3 (key on). If the inboard side of fuse 3 doesn't have power, check both sides of fuse 1 (key on). The object here is to ascertain if there is a loose wire on the back side of the fuse block. There is a remote possibility that ignition switch B to A is defective, but that runs lots of things and should be noticeable, especially on a Tach car. FYI, fuse 2 is normally only used by Cougars, as they have more "stuff" that needs power than a Mustang.