extruder not zeroing Z in middle of bed at beginning of print

Get us a screenshot of your start code.

IMHO, you have two problems.

1. Either your bed is not leveled to the hot end or your z endstop screw is too long and needs to be moved out. If your bed is not level, this would leave too much space when your bed hits the z-stop. If the z-endstop screw got pushed down too far, you are hitting the endstop before it comes up to the level of the extruder (this can also happen if your cables get caught between your bed and the endstop triggering it prematurely).

2. Not connecting is a different, and separate, problem. This has been covered on the forums. I have found that usually happens when there is an unexpected disconnection. Something like shutting your printer off when Repetier Host is connected to it. I find I have to turn my computer on, run Repetier, and then turn my printer on and it will connect. If I do not get the connection, then I would turn my printer off, restart my computer, and then turn the printer back. Generally, you want to the hear the New Device Detected ping when you turn the printer on or you might have a problem.

Just my two cents. Hope it helps.

I am not an expert coder, but this what I am seeing.

Wardjr.'s code homes to X193 and Y187. This is to the top right corner, and probably where you have your home set to. This is where my printer homes to as well. Then the code waits for the extruder to temp up, and sets z to your first layer height. All the while with the X/Y in the same home position.  The F3000 that has "center z head" commented is the same line commented as "set feed rate (speed) for first move" in the screenshot g-code. As I read it, there is nothing in the first G-code to center your X/Y on the plate. This should not be a problem if the bed is leveled and your first layer is set to the right height. The extruder will be off to the side, but the z will align to where it is supposed to be. This is what my printer does, and is normal.

Your set of g-code does show a line of code that looks like it is centering the extruder in the X/Y at 100, which would be the middle of your plate. However, the z has no feedback connection to the position of the extruder. The z should move as programmed, up the end stop, then down the amount of your first layer before printing. Where you position the extruder shouldn't really matter, as long as your bed is leveled within a paper sheet's distance when the z is homed, and your first layer height is not too big. I would check what your first layer height is set to.

thanks wardjr. I will copy your codes exactly. sometimes that is a problem for me since I am not sure if a space exists before or after a letter or punctuation. thanks for being so exact and brief in your instructions though for me it took me a little time to understand that your meant repetier host when you typed RH. (at least that is what I hoped you meant!). thanks again.

Short version is if your bed is leveled properly and your first layer height is set correctly, it should not matter if your extruder starts off the plate or in the center. When the print starts the extruder will go to the right place and at the right height.

As Wardjr said, you need to make sure your printer shape settings match your actual printer shape.

thanks Morganism. I will check all you said and do appreciate and understand your shorter version. will try it next week when I return to school. thanks again and I hope, really hope, to let you know that it is working. it used to be a real work horse, dependable. not for now!