Xerox Phaser 8400 Front Cover Open

You can download the service manual free at ww.eserviceinfo.com

I posted a problem with the phaser 860 paper jam. I found 2 broken sensor flags and am ordering the parts.

sounds to me like one of two things has happened.
More than likely the actuator tab on the cover snapped off,
Look for an opening around the edge of the cover , there is a cover interlock switch in there. Note its position and look at the cover to verify there is a tab on the cover to actuate the switch, Or you may have a loose connector on the interlock switch, or a bad switch, although I have never seen one of those switches go bad.

Here is the Xerox support page for your printer. It even has a movie on removing paper jams.
http://www.office.xerox.com/perl-bin/product.pl?page=sprt&product=8400&country=United%20States&language=en#_manuals_and_documentation_

What has most likely happened it the tab that actuates the cover switch has broken off. What you want to do it open that cover and look around the edge where it meets up with the other cover. There will be a hole, I would say about a half inch long and about a quarter inch wide where there will be a switch. Look at the exit cover in that area and you will probably see where a tab was, and is not broken off. You normally can fix it by making a couple of small holes in the cover and epoxying a paper clip in that area as a new switch actuator. You have to break or cut the paper clip to the proper length and so you have 2 ends to pop through the cover and epoxy it to.

8650 or 8560?
If its the 8560 you just take the screw out of the back and lift uprards about the middle of the cover. The front cover holds the front together and will pop off.
If you have the MFP version. you will have to take the scanner DADF section off before removing the covers

1. The top cover hinges are not connected to the ink slider bar properly. - Open the top cover and snap the hinge arms back into place and close the top cover. Check for proper operation. 2. Customer has not loaded the ink sticks properly and the top cover will not close properly. - Verify the ink sticks are loaded properly and that the customer is using proper Phaser 860 ink sticks. Close the top cover and check for proper operation. PARTS:Parts are listed in the order of highest probability for repair. NUMBER QTY DESCRIPTION PROBABILITY% MODEL S/N FROM S/N TO S/N 200469000 1 COVER; TOP COVER

What has most likely happened is the tab that actuates the front cover has broken off.
When you open the cover, you will see a bar code with some numbers under it. Look toward the top of that cover above that strip. There should be a piece of plastic about an inch long and thinner than a popsicle stick.
They have a tendency to break off.

Well here is what I can tell you.
Open the front cover. Staring you right in the face should be a bar code/number sticker. Look forward from that and there shoule be a small plastic tab, about a half inch long and less then the thickness of a popsicle stick. It is the front cover interlock switch actuator. It may be broken off.
Or look for the opening where that tab should slide into the machine the switch may be dislogded or broken.
Probably that tab has broken off not actuating the switch on that cover.

There is a flag sensor on the registration assembly that is possibly broken.