Left side of fuser
Teflon roller grey
Pressure roller
orange
HP use a consistent set of error numbers across their laser printer range. The full list is here.
This page is concerned with the fuser, the part of a laser printer that adheres toner to the page. Fusers give these errors:
In a perfect world the precise meaning and tests to prove what has gone wrong would be given in the service manual for the specific printer. The service manuals vary in quality and some are quite vague. There may also be inconsistencies and overlaps in meaning. However the manufacturers service manual has to be the primary reference - if they don't know we are all in doubt.
Printers with an LCD display will display the error there.
Printers without a display may use a light pattern or sequence but interpreting it will mean looking at the user manual. With a full install of the manufacturers software the error may also be shown by the Windows printer driver. (Yes, a full install of printer manufacturer software can waste disk space, but sometimes there are utilities which give detailed error messages)
Another source of information is the embedded web server on network models. Type the printers IP address (discoverable from the config page) into a browser to look at the status.
Printers also have a status log which can be printed. It is usually in the test menu. If the fuser has gone you can't print it but there is usually an option to display the last few items.
There is more on how to identify and fix fuser problems here.
Two main things go wrong with fusers:
Some of the more complicated errors need information about how fusers work.
A laser printer fuser makes toner powder adhere to a print medium such as paper using a combination of heat and pressure. Heat softens the toner and pressure forces it to adhere to the surface. On older printers there is usually an upper heated metal roller to provide the heat and a lower rubber roller on springs providing the pressure.
Most recent HP and Canon printers have replaced the top metal roller with a film of non-stick material like teflon. The main advantage is a significant cut in power consumption"
The fuser needs a fairly powerful heater. A 60 ppm printer is raising 300 grams of paper to 150 centigrade in one minute. Power for the fuser heater usually comes directly from mains (line) voltage. Power to the fuser is controlled via a triac or some other semiconductor relay device which turns it on and off to reach the correct temperature.
The power needed by the fuser can mean the support circuitry is a bit complicated. Power comes into the printer on a board called the low voltage power supply (LVPS) so the fuser power is usually switched from there.
A processor called the DC controller (or engine controller) provides motor and power control for things like the fuser. The actual fuser control relay may be on the LVPS but its signal comes from the DC Controller. (On some recent printers the DC controller might be integrated with another board so puzzling out the interconnections takes time).
The DC controller also reads sensors - the thermistor on the fuser and the various paper movement opto-sensors.
The DC controller acts as a feedback loop to control fuser temperature, turning the triac on to make it hotter then sensing the temperature rise via the thermistor and turning the power back off when the required temperature is reached. The temperature may be varied - hotter for heavy media, cooler but slower for media like transparencies.
Just in case the DC controller, triac or some other component goes wrong the fuser also has a thermal switch or fuse and this will pop if the fuser gets too hot. Some will reset when they cool down.
When the printer reports a fuser error this is genuinely most likely to be the fuser itself. However the fault could lie in the sensors, connectors, DC controller or the low voltage power supply board. Actual fuser faults can often be spotted by visually examining the object and perhaps measuring its resistance with a multimeter.
HP generally recommend a really simple fix; turn the printer off, wait 30 seconds (or perhaps 20 minutes) then turn it back on. That might sometimes work and since it is simple it is worth trying.
The printer electronics tries to spot problems with the fuser. It has a small collection of tools to do this. The thermistor will report temperature errors - sometimes there are two of them. There are one or two paper sensors so the electronics can check the timing of page edges. Printers can also measure the fuser power consumption - and most will at least report when it has gone open-circuit. The printer also stores its page-count and some idea of page cover - which also has an impact on fuser life. The electronics can't see the print quality but the user can.
Some of the most common faults may not be spotted by the printer electronics at all because the fault is a mechanical failure of the printer roller or its equivalent film sleeve. The user spots the problem on the printout. The initial problem is often grey marks down the side of the page that gradually worsen.
Marks down the side of a page are called "edge wear". The cause is the difference in pressure between the point on the roller where there is no paper and where the paper makes a gap 0.1mm thick. This distortion gradually breaks up the teflon on the roller or the film and it begins to de-laminate from the underlying metal. At some point the edge of the material will fail altogether and the marks will become continual and obtrusive. The printer usually has no way to know this is happening because the film next to the thermistor is intact. However it will be keeping a count of the number of pages printed and making an estimate of when the problem is likely to set in. Mono printers prompt the user for a "maintenance kit", colour printers prompt for a fuser.
More erratically marks can appear in the middle of the page perhaps because an object like a label has stuck - it might dislodge but the adhesive might stick to the fuser roller. Sometimes this kind of problem can be solved with a cotton bud and alcohol. Never attempt to remove a label from a fuser roller with a sharp object; it will scratch the roller and the mark will be incurable.
Marks at intervals down the page usually happen at a regular interval which corresponds with the circumference of one of the rollers in the printer. The service manual often gives a list, often under a title such as Defects Ruler
.
Another way to discover if the problem is the fuser is to perform a stop test. Set a test page away and wait until it is just entering the fuser and then open the lid. Is the defect visible on the loser toner that hasn't yet been fused. More details here.
Printer electronics don't incorporate a camera looking at the output (although they might in future). The printer has no way to know these marks are occurring. Some recent fusers do carry a charge on the fuser roller or sleeve and the printer electronics might sense a change in that.
More on how to identify and fix fuser problems below.
In most cases the "50 errors" indicate that printer firmware has found a temperature problem with the fuser. A board called the DC Controller tells the power supply to turn the fuser heater on and off. The fuser has one or two thermistors to measure the heat on the rollers (and in some cases the exit temperature of the media). The printer firmware gives an error if the temperature is wrong given what the DC controller told the LV-PSU triac to do and what is being returned by the thermistor.
This is often straight evidence that the fuser heater has failed. Some HP material says "a low fuser temperature error has occurred in the main thermistor" meaning the thermistor shows no temperature change. Experience suggest that it is unlikely that the thermistor itself will have failed, it is more likely to be a heater failure.
All fuser heater elements are brittle and may break.
Many fusers including older HP and Canon devices use a halogen lamp in an aluminium roller coated in teflon. A common fault at shipment is that the lamp falls out of it's holder. It's usually perfectly good and can be replaced quite easily but of course it would be better if this never happened. Manufacturers and refurbishers spend a lot of time and effort designing foam end-pieces to try to prevent a jolt dislodging the lamp.
HP and Canon now use instant on fusers. The heater is a ceramic strip with a teflon sleeve moving freely around it. The heater is less vulnerable to being damaged by a jolt but can be cracked if the fuser is dropped.
If the heater is broken it will show as open circuit with a multimeter. Heater circuits typically have a resistance of the order 100 Ohms (it could be as low as 20 or as high as 200 depending on model).
This is also called "Slow Fuser", "timed out" and "a fuser warm-up service error has occurred". The temperature of the fuser did rise but not sufficiently in the time allowed by the printer firmware. The fault might occur within a few seconds of power on, or after a page has printed.
This error is less certain to be cleared by a new fuser so other issues might be worth examining. First plug the printer directly into a wall socket. Extension cables and surge protectors can create a voltage drop that allows the printer electronics to work but causes problems when the powerful fuser heater cuts in. Don't plug printers into a UPS or inverter - most of them can't drive the heater and the voltage and frequency will fall so that the fuser can't reach temperature.
50.2 errors are essentially a judgement made by the printer firmware. The fault is apparently common on the CP3505 when printing envelopes and can be cleared by updating the firmware.
A fault in the low voltage power supply (LV-PSU) could also cause this - the triac might partly fail allowing the fuser temperature to rise a bit but not adequately.
Really weird faults like an envelope getting wrapped around the fuser roller can also cause this sort of fault. The fuser roller does reach temperature but the thermistor fails to do so in the time allowed.
HP say "A high fuser temperature error has occurred in the main thermistor". The implication might be that the DC controller failed to shut down the fuser heater as the temperature rose. One possibility is fan failure or simply a lot of hard use might potentially cause the fuser to overheat. The most likely cause is the low voltage power supply which usually contains the control triac. If the fault goes to 50.6 then most likely either the DC controller or the triac on the low voltage power supply have failed.
Changing the fuser is unlikely to fix this fault. If possible swap the fuser into another machine and if that works swap the low voltage power supply to confirm the fault before buying a new LV-PSU.
Experience suggests high temperature is not a common fault. If there is no other printer available use a multimeter to check that the fuser heater has a "reasonable" resistance. If you can find the triac on the LV-PSU it will probably have failed close-circuit and can be replaced if you have soldering skills. If the triac has failed components adjacent to it are suspect as well.
Fuser drive or power unit error. Check that the fuser is for the right voltage (110V in the US 220V in Europe Ireland and the UK). This error tends to suggest that the line voltage is wrong.
In the US where the supply line is at 110 volts long extension cables or thin IEC cables could cause this fault. That problem is less likely in the UK or EU where 220 Volt mains is used and currents are halved - but its still a possibility.
A possible cause is that the equipment is being driven by a generator with voltage or frequency out of tolerance. The fuser's triac control circuit will not operate correctly if the power supply frequency is outside the range 40 to 70 Hz.
Attempting to plug a laser printer into a UPS will not normally work. The fuser will draw a very high current intermittently and this is likely to drag the UPS voltage and frequency out of spec.
This message is particularly common with the LaserJet 4200 / 4300 series where six printer models can take 3 or 4 fusers that are physically very similar. HP designed the fuser so that a jumper on the connector distinguished between fusers for the 4200 and 4300. HP didn't make the scheme extendable however so the 4200 printer can't directly detect the RM1-1082 intended for the 4240/4250/4350. Liberty Parts have an interesting article on this.
Printers also measure the thermistor(s) presence and resistance and most printers also have an exit sensor so the printers can see wiring differences between these.
Some printers say "Fuser voltage mismatch. Verify voltage model." for this message. The printer thinks a 110 volt fuser has been installed in a 220 volt model or vice versa. It may be measuring the temperature rise or in recent printers it may be measuring the current.
A 50.5 message is pretty conclusive. Either its the wrong fuser or the connectors aren't mating correctly.
Heater error. The fuser heater cutoff has operated (typically at over 240 Centigrade). The heater cutoff is intended to prevent overheating so this is likely to be the low voltage power supply or whichever board has the control triac on it.
Open fuser almost immediately at power up would suggest the LVPSU monitors power consumption and has seen the fault. Check fuser continuity with a multimeter.
This fault will usually appear about 5 to 15 minutes after the printer starts up - the fuser takes some time to go over temperature. Changing the fuser will not actually clear the fault because the problem is that the heater control is not turning off. The fault is most likely to be seating of a connector, the low voltage power supply or possibly the DC controller.
In some models "Fuser motor malfunction". On many recent fusers the pressure roller can be adjusted to suit thick media and material like envelopes. When the user selects these media in the printer driver the printer adjusts this setting using a motor - it is usually built into the fuser base. The printer will know that the mechanism is malfunctioning if it cannot adjust the fuser and see the home flag change. There is no very specific reason why the motor and sensor should fail other than that they work in a hot environment. Attempt to rotate the components by hand. Service technicians will know ways to observe the fuser in situ, the mechanism should operate and go to it's home position when the printer starts up.
The same 50.7 message is apparently used on some printers where the fuser has it's own drive motor. Printers like the P4510 should probably give a "59" Motor Error for the fuser motor
The 50.8 and 50.9 errors are generated by fusers that have a secondary thermistor. In the case of the HP LJ 4250 and 4350 its in the exit flag and monitors the pages exit temperature.
Break in the sub thermistor. Turn the printer off and remove the fuser. Measure the resistance between the relevant fuser connectors (see the service manual). If it reads 600 ohms or below (at ambient temperature), replace the fuser
Several of the messages give little doubt that the fuser has failed. If the printer has done in excess of 100,000 pages of print and has a broken heater circuit, or if toner is not adhering to parts of the page there is little room for doubt that the failure is the fuser.
Some codes like 50.2 and 50.4 might be the fuser but just might be something else - old firmware or a bad power circuit. In this case a bit of technical work is needed to find out what is wrong.
On older printer designs it is often possible to observe the fuser working, a warm glow can be seen through air ducts in the rear every minute or so. On recent printers this indication of life often isn't visible. However a fuser will generally retain some heat for a few minutes. If you take a fuser out of the machine when it should have tied to print and its stone cold that suggests either the heater is broken (check continuity) or the circuit that drives it has failed.
Diagnosing a fuser fault generally means getting the suspect item out of the printer.
Difficulty in changing a fuser varies greatly by printer model. Printers like the HP 4200N just require the rear door to be removed and two blue knobs release the fuser. The CLJ 2600N is rather more difficult, covers have to be removed and wires handled. More expensive printers tend to have nice modular fusers that are easy to replace. Less expensive models have fusers that aren't easy to change. If we wanted to be rude about the manufacturer we might say their budget doesn't run to a couple of self-aligning connectors.
Users need to make up their own mind whether they are competent to change a fuser. The fuser does involve mains voltage but so does changing a light-bulb. Always turn the printer off and unplug it before working on the fuser. Fusers might have exposed metal parts that carry high voltages with the power on. Be wary about touching any of a fusers inner parts immediately after it should have worked. Inside a fuser gets scalding hot in operation.
Taking the fuser out of the machine is also a way to judge how easy it will be to fit a new one. If the fuser isn't examined the printer is going for recycling anyway, it may as well be in bits!
However don't demolish your printer and then decide to call a service technician - they may be amused but uncooperative.
As a first step check the seating of any wires and connectors. If a connector is not mating properly the printer electronics will report spurious errors. Look for damaged or bent pins on connectors.
Next look at the fuser mechanism itself. The actual roller or foil is visible through the paper entry and exit slits - exactly how much can be seen varies by model. Turning the drive gear in the normal direction of paper travel it should be possible to see the pressure roller which will normally be reddish brown and the roller or foil sleeve which will be grey. They should be fairly clean over most of their width. On a film based fuser the sleeve will have a dark band at one end mating with a little carbon fiber brush - that is an electrical path not wear.
Sleeves and rollers often degenerate completely at the end of their life. It is possible to replace them and there is more on that below however the normal course is to replace the whole fuser.
If the fuser looks OK is it still warm? If the printer has been in use the printer will have some warmth in it twenty minutes after use. If the fuser is stone cold when the printer has been on then that implies heater failure.
Some fuser models are known for making groaning and clicking noises. A pair of rollers might not seem naturally noisy but the fuser rollers operate under pressure so it does take some energy to turn. The most common source of trouble is on low and mid range printers where opening the lid releases the fuser pressure and removes one of the drive gears in the chain. This makes it easier to remove paper jams. However it is sometimes possible to close the lid sufficiently to make its safety switch but not quite enough to fully engage the gears which then ride unevenly on their counterparts. This gives a noisy whining or clicking gear chain. A diagnostic here is that gentle pressure on the lid will usually change the tone of the noise. There may be visible steppings on one of the cogs. There is no permanent cure except to replace the offending cogs.
For instance the LaserJet 4200 and 4300 series have a known issue. The fuser was made easy to remove - its little worse than changing a cartridge. The problem is that the fuser doesn't always mate quite properly with the gear chain, and the drive cog wears out
.
Another problem occurs if the fuser has been idle for a long time. The pressure roller is constantly loaded against the heated roller by the springs and it gradually loses it's circular form. This results in a whump-whump noise as the roller turns. If you turn the fuser by hand the change in resistance with each revolution is noticeable.
Note that fusers should be stored with the roller pressure released but this is easily forgotten. Over a couple of days with pressure released the roller should return to its proper shape.
Audible problems are notoriously difficult to trace because it take very little energy to make an audible noise. There are more hints on tracing them here --
To test the heater circuit look for the power connector. There will normally be two or three heavy duty terminals two of which carry the power for the heater. Others will be the fuser ground wire and possibly a sense connector to the thermal cutout. Use a multimeter to measure the resistance through the heater. Depending on the size of the printer it is likely to be in the range 20 to 200 ohms. Open circuit or a very high resistance implies a broken heater. A short circuit or something under 5 ohms rather implies your measuring the wrong thing.
The actual resistance of fuser heaters might be expected to be characteristic of the design but apparently that isn't always so. For instance the CLJ 2700 service manual says:
If the resistance is not 5 ohms to 1 kohms (100 to 127 V) or 20 ohms to 1 kohm (220 to 240 V ) replace the fuser.
That is a wide tolerance! If in doubt consult the service manual for your printer. They don't always give figures and if not make an educated guess.
A fuser resistance of 150 Ohms on 220 Volt Mains will draw about 1.5 Amps so the heater is about 330 watts. That seems about right for a fairly slow printer.
A fuser resistance of 20 Ohms across European mains at 220 Volts is going to draw 11 Amps - 2420 Watts. That's the kind of power we might expect to raise the fuser to full temperature in a few seconds, which is what fast modern printers aim to do. A much lower resistance would raise questions - there would be a current limiter to prevent the printer blowing fuses. (US models have half the resistance and twice the current)
The thermistor(s) may need checking. The connectors for these are usually smaller and there may be half a dozen pins - some for the paper exit sensor and suchlike. Thermistors will typically have a negative thermal coefficient - they have a high resistance when cold. Actual resistances vary but a cold resistance of about 3 mega-ohms and a hot resistance of 50 kilo-ohms might be typical. There is a lot of room for variation on thermistor design. At a workshop bench it is possible to warm the thermistor momentarily with a coolish soldering iron but that might be in the "do not attempt this at home" class of comments.
Historically it was often possible to repair a fuser with a new heater and hot roller. Doing this as a local workshop or DIY job has been less common in recent years, perhaps because a one-off job can take some time and the result doesn't always last a long time in the printer.
Lack of interest in repair has created a chicken & egg problem; parts aren't as readily available as they might be because no-one buys the parts.
Manufacturer attitudes on making fuser spares available vary. HP and Canon parts for fusers don't seem to be readily available. Brother do make the parts available - which is a point in their favour.
Refurbished fusers are units repaired to a professional standard.
We sell refurbished fusers because they are significantly cheaper than manufacturers originals. We find they are somewhat less reliable, so our general advice is that if you rely on a single printer and cannot tolerate it being down for any time buy a manufacturers original fuser.
Incidentally DON'T rely on one printer - they do fail and you won't always be able to get spares the next day. If you want someone to argue with put the thing on a maintenance contract. Reasonably capable mono printers cost less than £200 (and cheap to buy, expensive to run ones that will get you round a problem sell for £70.)
At one time refurbishing fusers was something workshop engineers would do on slack Fridays (Friday afternoon jobs). We think most refurbished fusers are being imported from China (or other BRICs) these days.
The idea that refurbishing can be done professionally deserves a bit of expansion. Refurbishing one fuser is a difficult job; it requires the ability to remember the jigsaw of fuser parts and a certain amount of physical dexterity with small parts. A significant problem is to get a film-sleeve, lubricant and (possibly) heater to the right specification. Manufacturers prefer to sell new fusers so they either do not supply parts, or don't do so economically. Parts used are ‘ compatibles ’. Refurbishing is one of those jobs that might be done in small numbers locally but tends to migrate to big facilities. The result is that refurbishing is done formulaically rather than professionally.
We used to sell a few fuser films but found it troublesome and stopped. But it is mainly the film that fails and not selling them is an annoyance - this is something that ought to be possible. So we are reintroducing them.
Repairing a fuser by replacing the film requires some knowledge of how fusers work and for the first few devices it needs patience. It won't invariably be successful both because it's difficult to be sure about the quality of the film, the lubricant and your own work.