How do I fix the top sliding bar on my Xerox Work Center XD 103f copier machine that gets stuck, after I turn on the copier? When it stops, it starts flashing codes 4 and H, or E and F.

SOURCE: Xerox Copier Machine - Error U4

The fuser is not warming up.
On that machine under the web there is a thermal fuse on a white plastic mount, it has one screw through it.
It is most likely blown. Possibly caused by a jammed paper in the fuser.
That fusable link needs to be replaced.

SOURCE: Reset Xerox Copier Machine model No. 5825

your copier should be displaying a fault code, different codes need different reset codes - be specific

SOURCE: Xerox XC 1020 copier code H4

With "H4" flashing press:
1.Clear button
2.Auto button then again

3.Clear button
4.Auto button

It should be done quickly. If it's done quickly enough all lights on display should go off.

5.Enter number 14 (as if you are making 14 copies).
6. Press START/COPY button.

The machine goes back to normal. If not, thermistor on the fuser (heater) should be replaced.

SOURCE: Xerox 5760 Color Copier has fault 03-302 at start-up

On these codes, on the back of the machine, unplug the harness that goes to all the boards on each one of them. Unplug and replug them all.
Do this one at a time.
Unplug them on the power supplies and the vertical high voltage powersupply.
Be very careful when pulling off the plugs, some are hard to release the snap that holds the plug to the boards.
This harness has about 5 large wires on them, they are the DC Wires.
If this happens again, the vertical power supply may need replacing or and even both Low voltage power supply and High voltage power supply at the same time.
Also, this problem may also be associated to NVM corruption on the main board. The battery on the main board has a life for about 10 years. The NVM may be corrutpted and changed the values, so the machine may not start up correctly.
If replacing the NVM Battery(chip) the large thick one, the date needs to be checked on the battery, and the right NVM( chip) needs to be installed on the Right Main board, along with the Right eproms. They need to be matched before replacing.
Even if the chip is replaced, the NVM values need to be checked and set to the right configuration to the machine model being used. There are many areas to be checked and reset to the right configuration and if it is not done properly the machine will not work, giving constant errors.
This is involved technical service and if the machine is really needed, A Xerox service call is needed to do the repairs on this model.

SOURCE: scanning bar is stuck, won't slide, just clicks

Did you try unlocking the transportation locks? 
There are 2, one on the left side of the scanner and one on the top cover.

Here is a site with some pictures on how to do it.
http://www.photo-i.co.uk/Reviews/interactive/Epson%204990/Page%201.htm

Testimonial: "Thanks, feel like an idiot, definitely an id 10 t error. I never knew about the lock on the top,thanks for saving me time and money. "