Is this a problem? Extruder and bed report diff temps

[anon4321 16]

After sitting overnight, when I turn the printer on, the temps reported by the printer are

extruder 41 and bed 21. The room temp is about 22.

Is the extruder reading more accurate at hotter temps or is there an issue with the temp sensor in the extruder and will this cause problems during printing?

Unfortunately, I have no way to measure the temps directly.

 

[gr5 2,167]

This is a problem.

UM1 or UM2?

Set the nozzle temp to 105C and see if it boils water. If it does set it to 95C and make sure a drop of water does not boil.

If this test fails I'm not sure how to debug it. Typically the problem is with the wire on the top of a UM1 but you probably have a UM2? Further diagnosis is different depending on which printer you have. Do you have a multimeter?

 

[gr5 2,167]

By the way it should be accurate to about 1C and even an error of 3C is not a problem but 20C is bad. It should be just as accurate at 20C as at 200C.

 

[anon4321 16]

Sorry I should have indicated that it is a UM1. The bed is self made (Jason HK's)

I do have a multimeter. I might just give in and buy an Non-Contact Infrared Thermometer. I need to calibrate my soldering iron anyway...

 

[gr5 2,167]

Usually temp issues with UM1 are resistance (almost an open) in the cable at the top of the print head. There is a 3 wire cable running from the small circuit board on the head to under the machine. The problem is usually the wire above the top of the head. At room temp (any temp really) try pushing the head around to the 4 corners and watch the temp to see if it jumps suddenly. Also try poking the wires until the temp jumps. If this happens just switch to the alternate cable (meant for a second extruder) or replace the wiring.

FYI, the voltage coming out of the circuit on top of the head should be 0V for 0C and 5V for 500C and linear in between so 20C should be around 200mv.

If this voltage is wrong (and the 5V to the chip is correct through that 3 pin cable) then the problem is with the thermocouple. But this is rare - usually the problem is with the cable on top of the head.