1941 cadillac wont start batter is new . there is no lights. horn works.turn key push button nothing works

You need to do alot more checking before you post. Is there voltage present at the starter solenoid? is there voltage at the headlights, when switched on? Do you know how to use a test light to verify voltage? Is the battery a 6 or 8 volt one? Do you have the battery connected backwards,i.e. positive cable connected to negetive terminal?

The battery is 6v new. I just rebuilt the motor. The car is + ground. Starter just rebult.every thing is back the way it was.made sure all wire is ok.could it be amp gage?[

No, not the amp gauge. Do you have voltage at the starter? did you verify with a test light? If the positive ground is attached to a freshly painted area, clean that to bare metal. An open or disconnected amp gauge would not prevent it from cranking over, just affect the charging system.

Up date. It was the amp gage. Jumped it out now car starts. Thank's mike