Replacing Broken Thermistor (E3D Molex Micro Connector)
I unfortunately trashed my hotend while attempting to tighten what looked like a loose nozzle. I now need to replace the heat break, heat block, nozzle, and thermistor. I've been doing some research, and the consensus from these forums is to purchase the E3D cartridge style thermistor:
https://e3d-online.com/thermistor-cartridge
The leads for this thermistor end in a Molex Micro Connector, which is not on the Prusa. Is it ok to splice the original Prusa wires to the new thermistor, or do I need to do something different?
Thanks,
Chris
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
Hi Chris,
Great question. It's one I wish I had asked before I attempted to replace my thermistor with the E3D replacement because yes, it's going to cause you grief. So, I hope this explanation will save you the time and grief. The blue wires aren't long enough to allow you to put the connector in a position that won't interfere with your print. If you place the connector on the left side of the hotend (looking from the front of the printer), it's going to interfere with hitting the endstop. If you place it below the cable bundle, it's going to hit your print. And the wires aren't long enough to allow you to put it on the right side of the extruder. So, where does that leave us? You can either cut the connector off and solder the blue wires directly to the red and black wires or you can do what I did and twist the heater block/heatsink enough to allow you to thread the thermistor behind the extruder and mount the connector on the right side of the cable bundle where it won't interfere with your print. It's easier to thread the thermistor end than the connector end, but be very careful with the wires where they come out of the thermistor cartridge--they seem kinda fragile. I threaded the connector end because I had already mounted the cartridge in the heater block by the time I realized it was necessary to do this, and it was a bear to get it through. After I finished, I made sure to put a wire tie around the connector and wire bundle so that it doesn't slip out of place. Also note that the heater block must remain slightly twisted because the blue wires are so short, but this does not affect printing at all.
If you want to see photos, I can take some when I get home from work today. I hope this helps.
I'm curious if anyone else who installed an E3D replacement came up with a different solution.
Good luck,
Phil
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
As far as whether it is safe to cut and solder, I can't give you a definitive answer, but looking at the original thermistor cartridge assembly from PRUSA, the blue wires appear to be soldered to the extension cable. So, I would think that yes, it is safe to do.
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
Yes, you can safely cut and solder the wires. I've done it twice without any problems.
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
Here are the photos of how I placed the connector. Note the angle of the heater block--it's about 45 degrees, but it still prints perfectly.
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
So I finished the install. I purchased a new V6 kit from E3D, and made sure to grab a 40 watt heater. The heater cartridge was easy because they already installed the ferrules at the end of the wire to install into the molex connector prusa uses. I was able to install the thermistor with the connector without having to rotate the print head. Maybe they increased the length of the wires?
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
Very cool! Glad you got your printer back up and running and that you didn't have to twist the print head. My suspicion is that they didn't intentionally increase the length of the wires, but rather the length just varies from one thermistor assembly to the next. I likely just by chance got one with wires too short for the dimensions of the PRUSA extruder.
I don't know about E3D, but MatterHackers seems like they'd be willing to check the length of the wires prior to shipping and send one with longer wires if you asked. Just a thought to help others out.
Re: Replacing Broken Thermistor (E3D Molex Micro Connector)
I purchased two spare thermistors and both have wiring slightly longer than 1.75" between the connector and the potting compound on the thermistor. I have to say that E3D had amazing and fast service. With Fedex shipping and the black friday code it was cheaper for me to buy directly from E3D than any of the US distributors. What really amazed me was I ordered the parts on Sunday, and they were delivered on Tuesday. Crazy fast shipping from the UK.