Can't get hotend (E3D) to stay at 245°

So I decided to finally try my hand at printing the Taulmann 645 I've had sitting around for awhile. I cut one of the Garolite sheets I had to fit my print bed perfectly and clamped it down. I sliced up a beautiful Python-created vase and was ready to go. I set the hotend temp to 245°C to feed the 645 in and purge the hotend of the PLA that was previously in there.

My hotend turns up to the desired temp then immediately drops down to zero (I think, I never let actually run down to 0°). What the hell? 245° is well below my modified high-temp setting (300), I don't understand what could possibly be happening here. Anyone have this happen to them? Thermistor is secured properly as well, I checked.

 

I have a fan blowing on the Arduino/RAMPS board down below but that is it besides hotend/print fans. And I haven't added my LED setup yet so I don't have any aftermarket parts that require power except for the E3D heatsink fan.

EDIT - I just noticed a worrying symptom as well. Even though MC says the printer is connected and is reading the temps from the thermistors, the printer is not reacting to any commands: extrude, Z axis up, etc. Now I am starting to trip a bit, what is going on here?

 

Where are the polyfuses located? See my edit above, does that clear things up?

 

-_- I don't know why I asked that, they seem fine by feel. I haven't lifted the case up yet to perform a visual yet though. So I am still able to print with PLA, I have a print running right now. But it seems that if I tell the hotend to heat up to ~230° or higher it starts glitching. Could I have blown one of the fuses? I wouldn't assume that if I did it would still let the hotend heat up at all, at least that's how I would have designed it.

I don't like tilting the machine too often, so I'll get my wiring ready for my LED mod and install it this afternoon while doing a visual inspection of the fuses and report back. This is such an odd problem.

 

I blew my fuse and it was acting super weird. It mostly worked but would trip out.

You'll be able to tell pretty clearly by looking at the fuse. Mine was split open on the top.

 

Mike where did you find a replacement? Most of my go-to suppliers don't have them, and I can't stand ordering from Digi-Key or Mouser.

 

That's a bit of a story. I bought the 14A polyfuse to replace the one for the heatbed so I removed the 11A one that was in there. When the 5A one fried I threw the 11A one into it.

this is the replacement for the 5a: http://www.mouser.com/ProductDetail...GAEpiMZZMsxR%2bBXi4wRUNn/Ah8aJZRgTeQ0UjkRSX4=

 

Can you link me the 11 amp one? I think I found it but would rather have confirmation haha.

 

http://www.mouser.com/ProductDetail...GAEpiMZZMsxR%2bBXi4wRUBaq0BDiykw2BXkVAk2hXUU=

 

Thanks Mike, I just realized I have some serious research to do. Most of my electronics work is in very small amperage ranges; I just realized how odd it is to have the knowledge/experience that I do in hobby electronics but know absolutely nothing about fuses haha.

 

I'm honestly real bad about protecting my circuits. I really ought to pick up some high amp fuses to protect my power supply and buck converter.

 

So I checked my fuses and both of them appear to be in perfect condition. I'll try heating the hotend up to 245° again when I get home from work and report back. This seems very odd.