Why did obi wan take so long to send Luke to Yoda?

[Darth Yan]

In canon there’s a three year gap between ANH and ESB. Why did obi wan wait all that time to send luke to Yoda? What was he doing?

[Elheru Aran]

Current Disney canon: Luke is keeping busy on various adventures while Vader is chasing him.

Old EU canon: Luke kept busy on various adventures, with the occasional drop-in by Obi-wan.

So, basically, he never really took a moment to sit down and let Kenobi have a chat with him. Reasonably sure that even in the new canon he has the occasional whisper from Obi-wan in his ear, like at the end of ANH.

As to why exactly Obi-wan never says 'hey go to Dagobah' soon as Luke takes off the medal... we never really find out why. Maybe he was catching up with Yoda and Qui-gon. Maybe he thought Luke would be safer not actually becoming a Jedi until the Rebels could defeat the Empire. Maybe he just didn't have enough Force mojo to evoke a decent vision. Who knows.

[Gandalf]

Maybe Obi Wan and Yoda saw the events of ESB taking place and decided that they would be a good way to teach Luke humility?

[Patroklos]

He hasn't had alot of luck with this lineage. He might have wanted to see how Luke reacted to a few years of stress to see if the apple fell far enough from the tree before going all in.

It was also sort of important to make sure Vader didn't find Yoda. Perhaps Obiwan had some presentient knowledge of Vader being distracted during the events of ESB and that would be a good time to have Luke break off without drawing attention.

[Solauren]

I always assumed it was a simple matter of Luke not being in the right state of mind for the knowlege, and command, to be communicated to him.

I mean, for crying out loud, it was almost like a Force Compulsion.

As the grandson of the force, I can imagine Luke was rather resistant to Force compulsion.

[Formless]

It is implicit in the film itself that Luke's encounter with the wampa forced him to open himself to the Force in a way that he previously hadn't, thus finally allowing him to see Obi Wan's ghost for the first time. This was what Obi Wan was waiting for before he sent Luke to train with Yoda.

[MKSheppard]

Maybe he just didn't have enough Force mojo to evoke a decent vision. Who knows.

Most likely this, and a combination of "Luke's powers are not strong enough to receive a full signal".

In ANH, almost immediately after his death, OB1's able to send whispers and such to Luke during stressful moments, like during the DS1 trench run.

OR, perhaps he had to wait until he felt that Luke was strong enough in the force that he needed a teacher to advance further, beyond simple parlor tricks and lightsaber play (without decapitating one's self)

[Patroklos]

The last is probably most likely. Remember Yoda wasn't keen on Luke as it was when he did show up there, straight up saying so.