Turn signal relay, a burned out bulb, bad wiring/connection, or a bad mulitfunction switch. Check the relay and/or try replacing bulbs and use a liberal amount of dielectric grease to seat them.
If you had a bulb burned out front OR back then the outher bulb would flash real fast,, I would check the flasher unit itself it is usely found under the dash on the drivers side..I must admit, I'm from the OLD school good luck..
Looking for a Used Astro in your area?
CarGurus has 10 nationwide Astro listings starting at $4,500.
Search Chevrolet Astro Questions
Chevrolet Astro Experts
Related Models For Sale