Thevenin total resistence question

[sevenStarCola]

In left circuit, I try use thevenin to change circuit for 6 ome.

At first try I think total resistence is 3ome.
But after try that I notice that's total ome is zero..!

I guess because current soure is cutted(when get total resister), but not think clearly
can you help me..?

 

[wwfeldman]

not quite sure what you are asking.
nor do i follow what you wrote.

6 ohm in parallel with 3 ohm yields 2 ohm

2 ohms in parallel with a 2A source is 4 V

Thevenin form is a 4V source with a 2 ohm series resistor
shorted yields the 2A from Norton version