Re-Taping Fuser Thermistors: Step-by-step instructions for the Xerox C35/WC232/WC5632/WC5735 family thermistors Most old-school technicians remember a day when re-taping thermistors was a regular part of maintaining copiers. Modern techs are trained to simply replace the entire fuser modules. Since financial times are tough, more companies are looking to reduce their cost of parts by repairing or rebuilding their fusers. Few fuser parts are spared these days by the copier manufacturers, and while you can usually find good generic heat and pressure rollers, often the thermistors are simply not available. So that means it's high time we revisit the lost art of re-taping these little temperature monitors. Give them a new lease on life to help assure that your rebuilding efforts pay off. We'll talk generally about thermistor repairs, including what kind of tape to use, and then we'll go through a step-by-step thermistor re-taping instructional using the C35 style fuser thermistors as our model. Photo 1 In many cases, good aftermarket heat and press rollers (and maybe picker fingers), are all that are available. The trouble is that you can replace the heat roller, but if the thermistor head's yellow tape is nearly worn through, it may fail sometime during the fuser's recycled life. Then the bead of the thermistor ends up riding directly on the heat roll's surface; ruining both the thermistor and the fuser roller. To make sure this doesn't happen, you'll want to first remove the existing tape from the "contact face" of the old thermistor (the "face" being the part which makes contact with the heat roller's surface). Add only one layer of tape over the face and put one wrap of thermistor tape over the contact point of the thermistor's head. The reason it's important to remove the old tape and to only add one layer of new tape is that adding too heavy a layer of tape is not a good idea. You would run the risk of over insulating the thermistor, causing it to be less sensitive to temperature changes. Photo 2 Photo 3 Photo 4 Photo 2-4: Carefully remove the old tape, only from Contact Face of the themistor. Which type of Tape to use? You'll want to use an appropriate width of either "Kapton Tape" or "KT250" tape. These are available commercially in rolls of varying widths. Now for a good example of how you might put this marvelous heat resistant tape to work for you. The instructions and photos which follow are specifically for the Xerox C35 style fusers although the basic idea remains the same for just about any thermistor which has Kapton Tape around its head. INSTRUCTIONS: 1. Remove two screws and disconnect the two front Fuser Heat Lamp terminals to release the Thermistor / Thermostat Assembly (see photo #1). 2. Release the two thermistor heads from the assembly (1 screw each). 3. Carefully use a utility knife to slice the tape on either side of the thermistor's contact face (see photo #2 and 3). Do not try to remove the tape from the rest of the thermistor… only the part on the face which contacts the Heat Roll's surface. Peel off any residual tape on the thermistor's contact face (photo #3). You may want to use a magnifying glass to check your work. Be very gentle… you do not want to damage the orange spongy pad nor the thermistor's wires. Photo 5 Photo 6 Photo 7 Photo 5-7: Apply new Tape to Thermistor 4. Apply new tape to the thermistor's head lengthwise (see photos 5-7). Start it near the base on the side which has the contact face (see photo 5)… put it on nice and evenly, gently pressing it into the corner of the thermistor head (see photo 6) and then wrapping it around the thermistor's face, ending at the opposite side of the base (see photo 7). Use your thumbnail to press the tape to all surfaces thoroughly especially on the contact face. 5. Next you will apply a layer of tape in the perpendicular direction (around the base) to keep the first piece of tape better secured. (See photos 8-9. Do not cover the thermistor's contact face with a second layer of tape. Photo 8 Photo 9 Photo 10 Photo 8-9: Apply securing tape around the base.   That's it! You have given new life to your thermistors so they will last another full fuser life without a problem. Thanks for tuning in everybody. See you next month! u 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 ).