Extruder Won't Heat--Upgraded to E3D (Page 3 of 4)

Meters don't read low resistances well. What resistance do you get when you touch the probes together?

Ok, so your bed is actually 1.7 ohms or so.

12/1.7 = 7 amps -> 84 watts.

This should be fine. I'd imagine there might be some issues with the connector not being tight/clean/making good contact.

Try mouser or digikey. I don't have a part # on either site but I know you'll find them there. Make sure it is rated for 7 amps or more or it'll just melt again.

How long should I soak the nozzle and heat break in acetone to clear up the clog?

Yeah, that didn't seem to want to work. No amount of heat and force would clear it. I actually had to use a small drill bit on my drill press to drill out the piece of ABS that wouldn't come out of the heat break. All good now though. Hopefully I can avoid any more issues, because it's been one after another!

Always had a fan on. I made sure the bit I used was significantly smaller than the ID of the heat break.

The nozzle itself was clogged, and there was a piece of filament stuck in the heat break

I am really very sorry you are having a hard time with the upgrade.  3d printing takes a lot of patients and has a very steep learning curve.  I can assure you that if the E3d is that frustrating a stock hot end would be 10 times worse.  Take your time and follow the assembly instructions to the letter and there is no reason it won't work perfectly.
Give me or any other happy E3d customer 20 minutes with your printer and I guarantee it would be running beautifully.  I am seriously wondering how you clogged an E3d especially so early on.
I just removed the first e3d I bought close to 2 years ago.  It must have well over a thousand print hours on it.  It never once clogged to the point where I couldn't just run up the temp to clear it out.  Even then that only happened a couple times well into the 500 hour range.
I only replaced it to install the Cyclops it still works just fine.
We all want to help you figure this out but I can't  help but feel like some of the problems you're having aren't self induced.
So fix your thermistor and make sure it is properly strain relieved.  Then let's get you up and printing

How did you break the thermistor? Is it properly strain relieved? I have around a thousand prints on a single thermistor.

Got the thermistor wired back, and everything worked as it should. Then midway through the print it stopped extruding, and I'm jammed again. What would be causing the filament to jam in the heat break like that? And is there a good way to remove the jam without having to completely disassemble again?

I had a very similar issue to you.  My E3D just kept clogging and under extruding.  It turned out, that even though I was able to use it for about 2 months with no issues at all, the fan shroud on the heat sync was put in upside down, which made it so the plastic was melting prematurely.  That might be something you could check as well.

Well that's very interesting to hear, because I kept the fan orientation the same, and just flipped the shroud (unscrewed and rescrewed), and since I haven't had any clogs...