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Extruder temp fluctuating, won't go over 130°C

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Horrors!!! Was about to fire up the printer to print some X'mas goodies but found that filament would not load.

Using a temp gun, the extruder does not go over 130°C when trying to load filament or in heating/cleaning mode. Display starts off showing extruder temp at 25°C, then goes all the way up to 230°C on the display although the extruder only gets up to around 130°C (and is unable to melt PLA). The extruder temperature seems to fluctuate going up and down between 80 - 130°C.

I've tried testing the thermistor (values were slightly out according to the temp/resistance table) and replaced it anyway with a new one with no change in results.

If I unplug the thermistor, the display shows 10°C (can anyone try this and confirm this?). When I plug it in, it shows 25°C (room temperature)

At this stage I'm thinking it's the logic board in the extruder module that's fried. I'm thinking that unplugging the thermistor should show an open circuit error or should show "-" as the extruder temperature? Can anyone confirm this?

Specific printer model is a Da Vinci Pro 1.0

I suggest looking very closely at the wiring for the heater connection to the hotend electronics. Inspect the wire going into the connector to make sure the pins are fully seated and/or the wire is not starting to break.

Also trace the wiring from the connector on the hotend electronics back to the controller board; inspect the wiring into the connector for breaking wires and the pins are fully seated. Inspect the insulation on the wires running back to the controller for cuts or breaks in the insulation.

Another problem point is the wires going into the heater tube; look for shorted wires and or a breaking connection.

I've checked the wiring, the connectors and pins for a good fit, tried to wiggle them as the extruder was heating up and it didn't make a difference either. Monitor seems to report 2 times the actual temperature of the extruder.

OK, if the wiring looks good then my next step would be to take a resistance reading of the heat-tube.

1.Remove power from the printer via the power switch or to be sure remove the power cord.

  1. Depress the locking tab on the heater connection and remove from the hotend electronics PCB.

  2. Insert jumper wires; use standard breadboard jumper wires and insert into each terminal of the connector. It will be snug and should not come out of the connector female terminal.

  3. Attach a digital multimeter (DMM) in the resistance or Ohm setting with one test lead on each jumper wire inserted into the heater connector.

  4. Take resistance reading.

Reference attached pictures for measurement setup.

The OEM heater should be approximately 4.4 - 4.6 Ohms. Should it be much higher or lower then consider replacing the heater.

The OEM heater is 35 watts; a safe replacement is the E3D 12V 30 watt heater. Going higher than 35 watts may cause the controller board MOSFET transistor and/or the surface mount fuse to blow. That is not an easy repair to complete without removing the controller board from the printer.

E3D heater sources:

Amazon - http://bit.ly/E3D12V30WAMAZON
E3D - https://bit.ly/3boWxo3

i guess its the controll board. i own a junior 1.0 and a month ago after not using it for 3/4 year (no filament was avaible or overpriced) it showed me error 004 and temp was shown with 384° from start. After changing the Printhead against a new result was same. I then decided to buy a showroom-used junior mini w and a open smart tag at comprise.de (wich also have a repair-center for xyz-printers) cause repair would be likely same price and the old junior 1.0 also had a break in its printbedholder wich resulted in a difference of half a layer.

I'm thinking it might be the logic board too :( which sucks because it doesn't seem that many spares are available for sale nowadays..

How are things going?

Not too good.. Having trouble finding an extruder control board - xyz will only sell a complete extruder assembly for $170+. I have no way of knowing if that would even solve my problem - or whether the problem is with the main board inside the printer?

Did you have any success with the heater resistance reading? It has been my experience either the hotend gets hot or not at all if the controller board has a problem.

The heating tube is much more available third party and less expensive than any XYZ Printing part new or used. If memory serves the hotend heat connection just connects from one connector to the other for power on the Pro hotend board.

Yes! I did test it and got a 4.3 Ohm reading for the heater. While cleaning the extruder nozzle on one or two occasions in the past, I did touch the wire brush to the heater element and cause a small spark.

You mentioned the MOSFET transistor previously, I can only imagine that the additional current and surge in power may have potentially damaged the MOSFET.

Any luck on a resolution to the heating problem?

Hi dweith, thanks for checking in. No I have since de-commissioned the printer and I am keeping an eye out for spare parts. A bit of a shame to throw it out but there are not many spare parts out there.