Heater not heating up above 140C

Hi all,

I finished assembling the printer. When I first connected the heater and thermistor, I heated it up, it quickly went till 185 and maintained it. Now I have assembled every thing and want to start printing. But the heater is kind of struck around 138 to 148C. It is not heating beyond that. Not sure what is the reason. Is it because it is not getting enough power? How much Amps should be going to the resistor?

If you reached that temp before, you don't have a power issue.
What kind of heater are you using?
Resistors: Either you have a foil type resistor, which burns out quickly (1-2 uses). Or the wire wound resistor, which may be shorting out during expansion while heating.
The thermistor may be shorting out also. It could be fouled. Or not the right one selected in your firmware.

I'm having this same issue I recorded it...
YouTube
I've tried different heater resistors and thermistors and different power supplies.
This email from POLYPRINTER helped, but alas I'm not printing yet(my reply is in bold)

But failure to reach temperature can come from several things:

Too much resistance.8 Ohms
Not getting full PWM on-time. How do I check this? I have an O-scope
Too low a voltage.

The voltage is easiest. Measure the power supply voltage while the heater is on, and see if it's what it is supposed to be. 11.57 Volts across pos/neg terminals to the Board PS input when it's up to 145 deg. Before heat is turned on voltage is 11.82 PS input

Then also measure it when the head first begins to heat up 11.59 volts across pos/neg terminal input to the board , or is cold - you can disconnect the head heater and measure the voltage to the heater when it's disconnected Heater disconnected heat turned on 11.82 across PS input 11.77V across heater terminal- , and even better, when it is connected and beginning to heat up Heater turned on leads across heater terminal 11.5. If it's not nearly the power supply voltage, the PWM isn't getting to 100% or there is resistance somewhere else in the circuit (but if so, it's going to be getting hot wherever the problem is).

You can also, with the head heater disonnected fromthe circuit, measure its resistance - it shold probably be about 6-10 Ohms 8Ohms if it's a 12v heater, or 25 to 40 Ohms if your printer uses a 24v supply. But you can ask on the user forums what it should be, I suppose.


Let me know what you find, if anything.
I do have a second power supply and it reaches 12.2 v across the input terminals and 12.03 when the heater is on. Also 12.03 across the heater terminals when it's on.
PolyPrinter