Rapid extruder temperature spikes both ways

I tried searching and found many issues with getting to temperature but this seems to be something different and I couldn't find an exact senario so I will put myself out there and make a thread.

I was about an hour and a half into a 3 hr job, using PLA that seemed to be printing great at a solid 200 degrees. no heated bed.
After a good half hour of watching it I set the timer on my watch for 10 minutes and was coming to check it every 2 - 10 minutes and it was going awesome! My first real print as I just got my robo a few days ago and am of course learning, I was finally feeling victorious lol.
Should have known better.....
I check on it for like the 20th time and it is starting to print off, a little globby and stringy, I look at the screen and the temperature is jumping all over the place! spike to 275 then down to 90 up to 230 down to 100 back up to 265 etc... etc... Cold extrusion prevented errors repeating as the temperature continually goes crazy.
I try countering manually and it just jumps too fast so I kill it.
I started it up briefly to see if anything was fried and it came to temperature nicely and seemed to be steady but I only gave it like 30 seconds as I was worried and turned it off again.

Now I'm worried to even start printing again, I dont want to burn anything out if I can't control it.
I wish I had a screenshot of the temperature graph, the red looked like the stock market the day before Y2K. Or an EKG of a seizure victim. Major erradic spikes if you get the point.


Anybody seen that before??
Also I should add I think my machine is one of the earlier models as I dont have any of the mods that seem to be included now, don't know if that makes a difference.

 

most likely a contact problem. Maybe a soldering point that's not good (by the thermistor, or on the board).
or less likely the thermistor is damaged.

 

yup definitely a loose thermistor

 

Thank you guys so much for the point in the right direction. I gave both wires a little wiggle to start and will see how it goes, Heart sank thinking the worst.
I don't want to remove the yellow thermal tape just yet, If I am staring at it straight on from the front of the machine is the thermistor on the front or the back?

 

Start from your ramps board and follow the wire to the extruder. I believe the extruder thermistor is on T0.

 

Your the best guys. Thanks.
Update after wiggling the wire a little and re running the job over an hour ago, temperature is dead solid.
I will for sure get in there after it is done and secure it.
Thanks again!!