Yes, they're rebuildable. Sometimes they need so much that it makes more sense to just buy a new one. I took mine in to a shop at the end of last season and they tested everything. The starter was fine, but the solenoid was intermittent. I think the total cost was about $30. It certainly was worth it to have my starter tested and a new solenoid installed. I think they had ballparked a quote of $100 if the starter had needed a basic rebuild.