Well wouldnt think adding the heal ability to a sensor tower was so hard according to this, except my sensor tower just sits there and diddo
added the button as well, wont heal marines or anything.
Under the Hood, the unit has the ability, energy, effect, all the actors, no behaviors [medivac has non either], and everything seems right in data editor.
Tried to create another unit from scratch with medic -heal and that was a no-go as well. What am i missing?

Moved to the correct section.

Those instructions work for other buildings, such as a Barracks. I'm not sure what specifically about the Sensor Tower is causing it to not cast the ability properly. Look around at some of its properties, or try removing things like the radar until it works.

Well i also found something interesting that the Sensor tower does actually heal marines but only when the marines are below a cliff level and diagonal left as seen in the picture.
The marines can do circles around the towers but nothing will happen until they are below and diagonal left...?

As for the direction limitation: Is that the direction of the tower?
Transports and Medics need to be facing a unit to heal it, the sensor tower is a building and only faces one direction...

Not sure about the height level.

Dabbu is correct in this, most abilities used by units in-game have an arc of 0, which means they must face the unit they heal, since buildings cannot face the unit they heal (Unless they have a turret of some sort) they will only heal units directly in front of them.

So to fix the heal problem, go into the ability and change the arc of the ability to 360. It should be at the top of scroll area. Also, if it doesn't work and you can't set it to 360 (I couldn't I think the 1.5 update causes it to set itself back to 0 if the number can round itself to 360 =( ), then set the number to like 359.3, and the building should then be able to heal the units.