Hotend Not reaching set temp after cleaning

Hi, I've been researching this problem for the last few days.
-Hexagon hotend , i3v 10, ramps 1.4, latest beckdac marlin fork
-Hot end normally reaches goal temp in about 5 mins (235c)
-Hot end was gunked up. I removed it, thermistor, and heater. Cleaned hot end.
-Reinstalled everything, thermistor is bottomed out in hot end. Heater is back where its always been.
-now even if I set temp to 270 it will go up to 190 like normal, but either stop there or go up about a degree a minute and might make it to 200 but never higher. Will eventually start dropping again.

I've checked the voltage on D10 and it stays around 12.1 volts even while the temp is going down.

Are there some voltages I should be checking? Could you point me in the right direction?

Any help is greatly appreciated. Thank you

You did tighten the set screw that pushes against the heater, right? Correct to assume that the LCD displays the correct set temperature, and that no error messages are displayed on the bottom row of the screen (min temp, max temp, etc.)?

Sounds like a bad heater. It could be that the movement during disassembly/assembly damaged the crimp connections just outside the heater. When the heat seems to be not going up any more, feel along the heater wiring to see if it is warm somewhere and/or squeeze the large insulator tubes next to the heater to see if that makes a difference in how the heater is working. You should be able to pull back the insulator tubes to look at the crimps, but a bad connection may not be something you can see.

You could remove the heater wires from the D10 terminals and temporarily hold them against the 12V input terminals. That takes Marlin and RAMPS out of the picture as far as what is going on - the heater should be on constantly as long as you hold the heater wires to the 12V source. Watch the hot end temp on the LCD. If you still have the same problem, it's likely time to get a new heater.

There really aren't any test points on the RAMPS board to monitor, but each of the MOSFET switches does have a status LED on the input. The LED for D10 is LED4, the second one up from the bottom left corner of the RAMPS board when the board is mounted on the printer. The MOSFET should be on (and power applied across the heater) when the LED is on. If you pull back the insulation tubes at the heater, you might be able to learn something by measuring the voltage between the two crimp sleeves.