Heater/Thermometer Diffrence in temp?

[Defect]

So I have a 150W heater in my sump and I had it set to 79 degrees. I have 2 cheap coralife digital thermometers one is in the sump near the heater and the other is in my overflow. Both of the thermometers read the same temp which was 81.3 degrees but the heater was still heating. Which do I trust more the heater or the thermometers? I turned the heater down to 76 degrees and it shut off.

Thanks

 

[Reefing Madness]

I had the same issue with mine, I turned the heaters down to 74-76 to get the correct temp in the tank.

 

[Defect]

So you think the thermometers are better to trust it looks like.

Thanks

 

[Reefing Madness]

Yea, I trust the digital thermometers more than our cheap heaters, especially if your running 2 thermometers.