Fixing the Fusers – Xerox WC 4250 & 4260

The WorkCentre 4250 & 4260 are newer models which follow the earlier WC-4150. If you’ve worked on the 4150 fusers, this will look very familiar. The procedure for taking it apart is nearly identical. In this article we’ll compare and contrast this newer fuser with its predecessor, and then get into the procedure for rebuilding one.

The 4250 version of the fuser is sold under the part number which retails for around $310.00. Xerox actually spares many of the parts within this fuser although the prices for the OEM parts are relatively dear. Fortunately some perfectly good aftermarket parts are out there at prices which make rebuilding these fusers a good way to reduce your cost of materials.

This fuser has a lot in common with the 4150 version of the fuser including some of the parts. There are also some substantial differences.

The most refreshing difference is that this fuser returns to a regular Fuser Heat Roll and Fuser Heat Lamp. The 4150 fusers had a heat element built into the heat roll, making it a complicated piece. These newer fusers are far more feasible for rebuilding because generic heat rolls and lamps are available, whereas on the 4150 you were pretty much stuck buying the costly OEM heat roll assemblies. The Fuser Lamp is a double lamp sharing the same ceramic connectors on the ends. Other parts which are different include the Fuser Heat Roll Bearings, Heat Sleeves (bushings), and Fuser Drive Gear. The Pressure Roller is also a bit different. The 4250 introduces a second Thermistor type, a non-contact heat sensor which we’ll refer to as Thermistor 2.

The fuser parts which are the same as the ones in the 4150 include the Picker Fingers, Exit Actuator Assembly, Fuser Idler Gear Assembly, Contact Thermistor Assembly, Thermostat (thermal fuses), and the Pressure Bearings.

Photo #1: Orientation                                  Photo #2: Remove CRUM Board holder

The 4250 version of the fuser has a CRUM Board (Customer Replaceable Unit Monitor) which was not present on the 4150 fusers. The CRUM Board is a little board with 2 Resistor / Fuses soldered onto it. Surprisingly the service manual showed a part number for the CRUM board (140N63354), but when we called it in, we were told that part number is not available to buy. Fortunately an aftermarket one already exists. When the machine sees a new fuser (or a new CRUM Board), it blows the first fuse. Then at the end of the fuser’s life cycle, the machine will blow the second fuse. Installing a fuser with both Resistor Fuses intact should automatically reset the fuser count. It appears that you can still reset the fuser counter from the diagnostics the same way that the 4150 fuser count is reset.

The fuser comes apart rather easily, although there are a few tricks and potential trouble-spots to be aware of, particularly during reassembly. Let’s get right into it, shall we?

Fuser Disassembly Procedure:

First let’s get oriented. The “top” of the unit is the part which has an opening to the Heat Roller where you can see the Picker Fingers. The “outside face” is the ribbed cover which is facing out at you when you open the door on the machine to get to the fuser module (See Photo #1). The inside faces into the machine when the fuser is in place – it has the thermal fuses and thermistors and the fuser connector. Then the “rear end” is the geared end of the fuser on your right in the photo and the “front end” is on your left.

1. Remove the CRUM holder assembly (2 screws) (see Photo #2). Then you can remove one screw which keeps the CRUM board captive. The CRUM Board has two components soldered in place which look like simple resistors but these also serve as fuses which the machine blows during the fuser’s life-cycle (see Photo #3).

2. Check out the Fuser Heat Lamp circuits and the Thermal Fuse to see if they are still good or if they need replacing. Often those components will turn out to be just fine. Disconnect the 3 Fuser Heat Lamp terminals from their spade lugs. Two were hiding behind the CRUM holder assembly which was just removed. The third is connected to the Fuser Thermal Fuse near the rear end (see Photo #4). If the Thermal Fuse (thermostat) is “blown” you’ll want to watch carefully for reasons why the fuser may have overheated. Dirty or damaged Thermistor heads are one possibility. Replace the Fuser Heat Lamp Assembly or Thermal Fuse Assembly only if needed.

Also check the Fuser Drive Double Idler Gear (found on the rear of the fuser, it drives the Fuser Heat Roll Drive Gear). This double gear is known to get “sloppy” over time. It can cause a thumping sound in the fuser area if it gets too wobbly. It should feel snug on its shaft.

Photo #3: CRUM Board Photo #4: Disconnect the 3 Fuser Lamp Terminals
(2 at the front, 1 at the rear)
Photo #5: Front End Screw & Spring

 

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3. Remove the Fuser Heat Lamp Assembly to get it out of harm’s way. If you first remove the front lamp bracket (1 screw), you can then slide the Fuser Heat Lamp Assembly gently out through the front end of the Fuser Heat Roll.

4. Next you’ll be separating the two halves of the Fuser Module. Release pressure by removing the two pressure springs (one front and one rear on the top of the assembly). Then remove two screws from the “inside face,” one near the top on the front end (see Photo #5) and the other is near the top close to the rear, geared end.

5. Gently separate the two halves of the fuser which hinge on each other at the bottom. (See Photo #6)

6. Concentrate next on the Heat Roll half of the fuser. Be very careful with the 4 Picker Fingers as you now remove the Heat Roll Assembly from its cradle (the fingers can potentially get damaged, and they would scratch the Heat Roll’s surface rather easily if you were not paying close attention to them). The Heat Roller Assembly lifts right on out now, along with its Drive Gear, Bearings and Bushings (there is one wire retaining clip which needs to be removed to get the Fuser Heat Roll Drive Gear off). With the Heat Roll out, you can now see the inside faces of the Thermistor Assembly (2 heads), Thermistor 2 (non contact), and the Thermal Fuse Assembly (2 thermostats joined in an assembly) (See Photo #7).

7. You should seriously consider re-taping the Thermistor heads using Kapton tape because if the tape wears through, it can cause fuser failures. Put one piece of tape along the length of the thermistor head, fold it neatly so that it continues along the back of the thermistor to fold over and adhere to itself. Then use a second piece of tape near the base of the thermistor to go all the way around at least one full time in the other direction to secure the first piece of tape. The second piece of tape should not wrap around the sensory bead end of the thermistor’s head (only allow one layer of tape over the sensory bead of the thermistor so that its sensitivity does not change too much).

Photo #6: Separating the two halves. Photo #7: Heat Roll Holder…
(the thermistors and thermostats)
Photo #8: Pressure Roll Removal
(Watch out not to lose the Static Brush which is trapped under the front end of the Entry Guide)

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8. Now you’ll be working on the Pressure Roll half of the fuser. Take off the Fuser Entry Guide (3 screws). Don’t lose the little static elimination brush (it contacts the Pressure Roll). It is trapped under the Fuser Input Guide near the rear end and will fall right off once the guide is removed. Also take off the Front Jam Lever and its spring (1 screw from the front) (See Photo #8).

9. Release the front Press Roll Bracket and slide off the front bearing. Then the Pressure Roller can be lifted out and the rear Bearing will slide right off as well. Under the Pressure Roller is a metal Cleaning Roll which is just sitting in a pair of spring loaded cradle-like line-bearings (remove it because it’s loose and will fall out easily).

10. During reassembly, there are a couple of important things to know. First of all, when you reinstall the Heat Roller, to avoid damaging the roller, you need to pull back all 4 picker fingers at the same time. I found using a pencil worked well. Hold it along the length of the fuser and lift all 4 fingers together. Second, the blue wire on the front end of the Fuser Heat Lamp Assembly goes to the spade lug which has the black wire, and the white goes to the white.

That should do the trick! Now to reset the Counter….

Resetting the Fuser’s HFSI Counter:
Resetting the HFSI Counter (High Frequency Service Item Counter) happens automatically if you install a new CRUM Board (or if you replace the two fuses on the CRUM). Or you can do it from Diagnostic Mode by holding down the ‘#’ key and then press the “Access” key. The Diagnostic Login Window will show up. Enter the password (the default is ‘1934’) and touch ‘enter’ (note that if you put in the wrong password 3 times, the machine will lock up for 3 minutes before you can try again). Now touch the ‘HFSI’ tab to bring up the HFSI Table. To reset the fuser’s count to zero, select the fuser on the list and then touch ‘Reset’ followed by ‘OK’. Now choose ‘Exit’. Touch ‘Call Closeout’. From this screen leave “Reboot Copier” set to “yes” so that your HFSI Fuser counter will be properly reset during the rebooting process.

Good luck fixing the fusers! It’s another good way to “go green” and save some green at the same time.

Britt Horvat
About the Author
Britt works for The Parts Drop, a company whose primary business is providing parts, supplies and information for Xerox brand copiers, printers and fax machines. You can find more information, including many of Britt’s past ENX articles on their website, www.partsdrop.com . If you’d like to read more about Xerox brand office equipment, there’s also a complete listing of past articles under contributing writers on the ENX website (www.ENXMAG.com).