Sun in the 3rd house (Sahaja, the house of courage) brings the significations of Sun, namely soul (atma), father, authority & government, into the area of courage, self-effort, siblings and communication. The 3rd house governs courage & effort, younger siblings, communication & skills, short journeys.
Results of Sun in the 3rd House
Sun is a malefic planet, so here it tends to bring low confidence, ego conflicts, trouble with father or bosses, and weak vitality focused on courage, self-effort, siblings and communication.The exact result depends on which sign Sun occupies here and the aspects it receives.
When It Activates
These results typically surface during the Vimshottari mahadasha or antardasha of Sun, and when transiting planets trigger the 3rd house. A well-placed Sun here supports bravery, initiative, talent and good bonds with siblings; when afflicted it can indicate timidity, lack of drive and strained sibling relationships.