Hmm, maybe you're right! I just checked the code for the Adafruit MAX31855 breakout board, and it has this:
if (v & 0x7) {
// uh oh, a serious problem!
return NAN;
}
// get rid of internal temp data, and any fault bits
v >>= 18;
//Serial.println(v, HEX);
// pull the bottom 13 bits off
int16_t temp = v & 0x3FFF;
Tomorrow I'll comment out that first if block, and test again.
Just to be sure: those washer style CHT probes are grounded at the hot junction, not T-. *)
Holger
*) Well, AFAIK that is.