New hothead, now thermistor not working. Any ideas?

Bambu Lab P1 Series Troubleshooting
1

New P1S, 5 weeks old, so our experience is limited.

So my 15yo was printing & 3 small prints went well. On the fourth, he had a birds nest & shut it down. The next day, I tried to print & kept getting strings & non adhesion to the bed. Found it clogged & removed the head & cleared the clog.
Tried again and same problem. It would drag the purge strip into the printing area & birds nest again.

He was printing in BB Handy & the print called for PLA but he likes PETG better & was printing with PETG. We have done this several times with no issues.

Anyway, I decided to install the spare hothead (.04). After watching a couple of YT videos, I changed it out & tried again (PLA this time). Same issue.

I have tried everything the Wiki said to try (plugging in in several times, (like 6 times, trying it each time) removing & reinserting the thermistor wires (4 times) & it still will not read or control the temperature of the printhead. Now I’m out of thermal paste & it doesn’t seem to be listed in the BBL us store.
(If I order some from Amazon, any recommendations?)

I have a multimeter but the leads are too big to contact the tiny pins to check resistance. The thermistor wires look good, but cannot tell if the solder joints are good or not under the heat shrink. I gently tugged on them & it seems connected, but IDK if it’s just the heat shrink holding it.

I have ordered a complete hotend replacement but it takes about a week to get to our rural area, which is why I tried to replace just the hot end.

Any ideas would be appreciated.

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You could try to plug in the (un-)clogged hotend to check if the problem is with the thermistor of the replacement hotend or the pins on the board. I have also found it helpful to have a few spare thermistors on hand.

As for the original issue, PLA and PETG really don not like to adhere with each other. So when alternatingly printing PLA and PETG on a (textured?) plate, you’ll benefit from more frequent plate cleaning. In particular the textured plate will work well for a while when alternating first layer materials,… until it very suddenly doesn’t due to built up residue’s in its valleys. Cleaning needs to be particularly thorough in this case.

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Thank you so much for that advice! As a newbie, I really appreciate it.
Yes, we are using the textured plate.
Who knows what the 15yo did? :grimacing:
I found a complete hot end assy on Amazon, so we should be back in business sooner than expected. Providing the circuit boards are ok.
I think the thermistor is the problem as the error (I should have mentioned that) said open circuit, so hopefully it is an easy fix.
I was really worried yesterday, but feeling better about it now!

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