My Am Reception Is Lousy .sometimes Just Static You Can Hear The Turn Signals In The Radio Fm Is Perfect

 

AM radio is tough to cure. The antenna pulls the signal in and needs to be in good shape AND have a very good ground. I would try one of a couple of things. First make sure you have a good ground to your radio chassis, this is important for any radio. Make it at least 10 gauge wire. The antenna can become 'worn' out due to oxidation. Remove the antenna and clean the mounting area as this is were older antennas grounded, often the ground area is on the innerside of the fender. A better fix is to replace the antenna with one that allows you to attach a ground wire to the threaded mount. Using a round wire end that fits, you can mount the antenna and connect the ground wire to a chassis point. Also make sure your battery ground connects to the motor, rad support(for the headlights) and to the firewall. Use at least 10 guage or heavier wire. This will help with grounding issues.
Aftermarket radios usually have whimpy ground wires which are marginal at best. It is a good idea to add a heavy ground wire to the chassis and on your amp(s). One reason radios of any type pick up stray electrical signals is because of poor grounds.