Bed heat not working after replacing thermister wire

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Vandal968
Posts: 212
Joined: Mon Jul 13, 2015 4:30 am

Bed heat not working after replacing thermister wire

Post by Vandal968 » Mon Aug 27, 2018 8:24 pm

The thermister wire for my bed heat died a while ago (1+ year). Since I was busy, I just slapped some glue stick on the bed and kept printing with heat off, the bed temp readout used to flip between ambient and 0 while printing which helped me confirm that it stayed broken. Two weeks ago, I finally got around to investigating. I found the bad spot in the wire and replaced the entire thermister wire from Rambo to bed. Thermister readings have been nice and stable, but I hadn't tried to use the heat until yesterday. Nothing. I pulled the bed heater and plugged it into a bench supply and it draws power. I started checking the Forum to troubleshoot and came across a message that says:

"If the bed temp drops to zero which should be a bad thermistor or wire, then the firmware will disable bed heating altogether as a safety measure." -sprior

Located in this thread: viewtopic.php?t=169

Is that true? And, if so, now that my thermister is fixed how can it be reset?

thanks,
c

Vandal968
Posts: 212
Joined: Mon Jul 13, 2015 4:30 am

Re: Bed heat not working after replacing thermister wire

Post by Vandal968 » Mon Aug 27, 2018 8:50 pm

Ok, if a thermistor reading of zero disables bed-heat as stated above, then it's only for that session. I just pulled my rambo cover and hooked up a meter, turned on bed-heat, got 24v. jumped between the rambo terminal and the bed connector and the bed heat works. That wire must have failed as-well :(

Good news is that wire is cheap. While I'm at it, has anyone found a good solution for these bed-heat wires like drag-chain, etc? It seems like the one weakness of the MakerGear design.

cheers,
c

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