Joh_1:18 No man hath seen God at any time; the only begotten Son, which is in the bosom of the Father, he hath declared him.<quoted text>
Then explain to me who this was please:
When Abram got to be ninety nine years old, then Jehovah appeared to Abram and said to him: "I am God Almighty".
This verse proves that no man has seen God. Even if you assume that Jesus is YHWH, it still creates a contradiction since no man has seen God. So the conclusion then is Abram saw neither the Father or the Son (based upon your own theology) since both are considered to be YHWH in your world view.
The correct interpretation of the verse comes from a Hebrew mind set known as 'Shaliah.' Though it doesn't specifically say that 'the LORD' in the verse is an agent of YHWH, this is the more preferred interpretation due to this law being throughout the Genesis account, and in general the bible. Plus we have a verse that plainly states that no man has seen God at any time.