I am using a MAX6675 board and a k-type thermal couple to measure temp. The problem is even when running the example the temp value keeps climbing.

MAX6675 test
C = 27.25
F = 130.10
C = 218.00
F = 816.80
C = 1744.00
F = 2624.00
C = nan
F = nan
C = nan
F = nan

I am using the max6675.h library. Is there a way to fix this?

#include "max6675.h"

int thermoDO = 4;
int thermoCS = 5;
int thermoCLK = 6;

MAX6675 thermocouple(thermoCLK, thermoCS, thermoDO);
int vccPin = 3;
int gndPin = 2;

void setup() {
  // use Arduino pins 
  pinMode(vccPin, OUTPUT); digitalWrite(vccPin, HIGH);
  pinMode(gndPin, OUTPUT); digitalWrite(gndPin, LOW);

  Serial.println("MAX6675 test");
  // wait for MAX chip to stabilize

void loop() {
  // basic readout test, just print the current temp

   Serial.print("C = "); 
   Serial.print("F = ");


edit: Added code (https://github.com/adafruit/MAX6675-library/blob/master/examples/serialthermocouple/serialthermocouple.pde)

  • 2
    Code? Wiring? ...?
    – Majenko
    Jul 3, 2018 at 18:03
  • I think your house is on fire. Or maybe your code is incorrect, but it's impossible to say when you haven't provided it to us.
    – Gerben
    Jul 3, 2018 at 18:52
  • The output does not look like it came from this sketch, quite apart from the values it prints. Your loop() function is coded to sample and print 2 lines every second: "C = .... \n" "F = .... \n", yet the output you showed has another line preceding each pair. Are you saying the sketch (or the library) is producing 3 lines where only 2 are coded?
    – JRobert
    Jul 3, 2018 at 20:48
  • I added a line that was just C= thermocouple.readCelsius() Serial.print (C)
    – Michael H.
    Jul 3, 2018 at 20:54
  • Please provide a picture of your wiring, or at the very least confirm that the pins GND, VCC, DO, CS and CLK do indeed go to data pins 2, 3, 4, 5 and 6 respectively - as declared in your code. I assume this is AdaFruit's version of the library? If this all checks out, then it's almost certainly hardware: the thermocouple, the MAX6675, or the Arduino itself. Jul 4, 2018 at 9:48

1 Answer 1


After test some other K-type thermal couples on this I am now thinking I just got a bad board. I was able to order a new one and it worked without issue

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