50.1 Fuser Error Low Temp – HP Laserjet 4000, 4050, 4100 Printer
The 50.1 fuser error is a low temperature error on the HP laserjet  4000, 4050, and 4100. Is the second most common fuser error found on this model. Why?  More things can cause low fuser temperature than overheat errors.  Below I will discuss a few things you can try to get your HP laserjet 4000, 4050, and 4100 out of its 50.1 fuser error and  working again.  For those of you that may need it, I will also  provide you with instructions on how to replace the  fusing  assembly  and a link where you can purchase a new fuser if needed.
HP 4000/4050 Fuser Assembly RG5-2661-000
HP Fuser for LaserJet 4100
Troubleshooting The HP Laserjet 4000, 4050, and 4100 50.1 Fuser Error
First thing to try in troubleshooting the HP Laserjet 4000, 4050, and 4100 50.1 fuser error  message is just turning off and on the machine. Once in a while these machine will get a sudden drop in power through a sudden power outage and the machine immediately goes back and checks the temperature inside the fuser  when it’s not properly warmed up resulting in a temperature low state with a 50.1 fuser error. Other time having too many electrical devices plugged into the same outlet or having these printers plugged into a surge protector or battery back up can have the same effect. Too many devices on the same outlet can cause  a sag in the voltage to all the devices. Whenever troubleshooting 50.1 fuser error in your HP laserjet 4000, 4050, and 4100 printer, HP and other technical resources will always want to make sure the machine is plugged directly into the wall and no other devices that draw a lot of power are on the same circuit as these machines.
Advanced Troubleshooting for the HP Laserjet 50.1 Fuser Error in a 4000, 4050, and 4100
1. If the message persists, reseat  the Fuser. If that does not work, replace the Fuser.
2. To check the Fuser, turn the printer off and remove the Fuser. Measure the resistance between the Fuser  connectors J132-1  and J132-2. If it is not within the range of 200k Ω  to 500kΩ, replace the Fuser.
3. If there is no continuity between the Fuser  connectors J143F  (neutral) and J142F  (hot) with the Fuser  removed, replace the Fuser.
4. If the problem is not related to the Fuser, replace the Engine Controller Board
Conclusion About the HP Laserjet 4000, 4050, and 4100 50.1 Fuser Error Message
Yeah, there are ways to check the OHM readings on the fuser  thermistors  but replacing the heating element will only save you a few bucks than replacing the whole fuser  so I’m not going to go into detail other than what’s above. Also, the Engine Controller is another option but after working on several hundred of these machines and only replacing one on a 4100 I’ll say that very rarely happens. Best thing to do is just replace the fuser. Under the instructions to replace the fuser  is a link to purchase a fuser. The fuser  is very easy to replace and no tools are necessary on the HP 4100 and only a phillips screw driver on the 4000 and 4050.
HP Laserjet  4000, 4050, and 4100 Fuser Removal
Note: Unplug power and communication cables and allow at least 10 minutes for cool down before fuser removal.
1a. 4100 – Facing the rear of the printer, press the left side (formatter side) of the rear output bin and release the hinge from the slot.
1b. 4000 – Facing the rear of the printer, pinch the right side of the Rear Output Bin and release the hinge from the slot.
1c. 4000 – remove the Left and Right Duplex Access Covers from the rear of the printer by pulling each from the bottom.
2. Rotate the output bin away from the printer until the right hinge pin is released, and then remove the output bin.
3a. 4000 and 4050 remove the two screws
3b. 4100 Rotate the two blue levers on the fuser assembly up to the unlocked position.
4. Pull the fuser straight back and out of the printer.
Hopefully, this article has helped you troubleshoot the 50.1 fuser error in your HP laserjet 4000, 4050, and 4100.
HP 4000/4050 Fuser Assembly RG5-2661-000
HP Fuser for LaserJet 4100
For More information involving Printer Repair take a look at this site: http://www.fixyourownprinter.com/
