Checking the Fuser Assembly in your HP LaserJet Printer  Always shut off printer and let the fuser rollers cool down before you do anything! By removing the fuser from the LaserJet Printer you can check the fuser rollers for burns and tears in the teflon, check lamp/thermoswitch for an open , check bearings and gears and determine whether the fuser assembly should be replaced.

HP LaserJet II, III, IID, IIID	Remove fuser from printer	Remove Cover	Check bulb & thermoswitch
	Open top cover, use long magnetic phillips screwdriver to remove four screws. Pull fuser assembly straight up and out.
SX	Remove left cover to access heater lamp connector, lay fuser on back, using an ohm meter with one lead on the lamp you should read 2 ohms on one side and continuity on the other. If not either your lamp or thermoswitch is open, causing 50 service Error. Inspect gears and roller.
RG1-0939

HP LaserJet IIISi, 4Si	Check paper out sensor
NX-RG5-0046		This wears a flat spot and will not make it much past 200k maint. Part shown here is gray, original color was black. It is recommended to replace the fuser at the 200k maintenance. Inspect roller, gears and pawls. Testing the thermistor, lamp and sensor.
To remove from printer: Open top cover, remove the four brass 4" phillips screws at the corners slide the fuser to the left and pull straight up and out. To reinstall angle right side in first slide into connector at right.
The fuser should always be rebuilt if it is squeaking, has tears or burns in roller or is grinding.

HP LaserJet 4,4M,4+,4M+,5	Remove fuser from printer		Test Thermistor and Lamp
	Open back cover remove the two screws that hold fuser in place lift slightly and pull straight back, Use a long magnetic phillips screwdriver between roller shaft or at stubby screwdriver.
EX/EX+ RG5-0454/RG5-0879	Check thermistor across top left pins you should read about 220k at room temp.		Using ohmmeter across large pins check lamp should read 2 ohms.
Note: Part number may or may not be stamped on metal plate (4,4M use 0454), (4+,4M+, 5 use 0879)

HP LaserJet 4V, 4MV	Remove Transfer roller first	Remove fuser from printer
RG5-1557 BX	Spongy black roller located directly in front of fuser, do not get oil from your fingers on these, note the position of the sensor just off center. The transfer roller just snaps into clips at both ends. Do Not put this back in and close cover after you have removed fuser.	Remove the five brass screws only, Look at the ends of the metal shaft by the tan plastic levers where the flat spots are. You will need to push to cover outward to clear the tabs then pull straight up. Do one side at a time. Uses floating connectors don't force in place!
Caution: This one runs very hot, always use power save feature on this printer

HP LaserJet 4L, 4P, 5P & 6P	Removing the Fuser	Testing it while it's out
	Coming Soon! 4L 4P 5P 6P	Looking at the fuser with the connectors in front, measure the resistance between the pins on the left connector it should read around 440k ohms. The right connector should read 25 to 30 ohms. Use a small resistor lead to make contact with the pins, be careful not to damage the contacts when testing. Do not use a paper clip! If either reading is not good the heating element will need to be replaced.
Check the roller sleeve over the heater for tears and the lower red pressure roller for excessive toner build up.

LJ LaserJet 4000/4050	Removing the Fuser	Testing and Inspecting
	Go here.	Locate the black connector at the bottom of the fuser. Looking at the fuser with the gears on your right side, measure resistance across to two larger pins it should read between 13 to 15 ohms at room temperature. On the set of five smaller contacts measure the resistance on the two right most pins it should read between 220k to 500k at room temp. If either reading is bad the heating element will need to be replaced.
Check the gears, roller sleeve over the heater for tears and the lower red pressure roller for excessive toner build up