# Which thermostat to trust (WSM)?



## oldskulldude (Mar 28, 2020)

Just purchased an 18" WSM and the lid thermostat reads 20 degrees hotter than the iGrill thermometer I have running.

I placed the iGrill probe on the bottom rack just above the water... I now know that was the wrong spot but either way...which should be trusted... 20 degrees seems like a big difference.

Thanks in advance.
OSD


----------



## 6GRILLZNTN (Mar 28, 2020)

The dome therms on Webers are notorious for being off.


----------



## chopsaw (Mar 28, 2020)

I boil test my lid therms on my webers , and they all test good . How long they stay good ,,, who knows . I just need an idea from it anyway ,,, I use an inkbird or thermo pro at grate level .


----------



## cmayna (Mar 28, 2020)

Put your igrill probe up near the WSM's thermometer in order to compare them or as mentioned, do a hot water test on both.


----------



## sandyut (Mar 28, 2020)

the dome one is useless beside filling the hole.  I use a thermoworks DOT on the grate surface.


----------



## Blues1 (Mar 28, 2020)

I'd trust the iGrill over the dome.


----------



## oldskulldude (Mar 28, 2020)

Thanks for all the input. I will do some further testing.


----------



## cmayna (Mar 28, 2020)

I use a Thermoworks Smoke unit on my Weber.


----------



## oldskulldude (Mar 28, 2020)

And you trust that over the built in thermostat?


----------



## BandCollector (Mar 28, 2020)

I work for a small business that sells and services natural gas/propane grills.  Both brands (made in the USA) we sell have built in thermometers.  I possess both brands and neither lid thermometer is accurate to any measurable standard.  I seriously doubt that any lid thermometer regardless of the manufacture is accurate.    They are mostly for show.

Better off using an Inkbird or other thermometer for monitoring temps.

John 

 BandCollector


----------



## noboundaries (Mar 28, 2020)

Probe placement can make a difference. My original WSM lid therm quit working long ago. I replaced it with a River Country therm, did all the boil and ice water tests and it's good. That said, I've learned a few things.

Temps are not constant across the grates. Top grate temp can be 50F higher under the top vent as opposed to the grate on the opposite side of the vent where the lid therm is located. Consequently, I'll rotate the lid to get an even cook.

I have the Ink Bird, Maverick, and a BBQ Guru grate probes. The IB gives a solid reading right from the start and matches my RC lid therm when placed below it on the top rack. 

The Mav and Guru each have an algorithm that averages readings over a longer time period. They both read low initially, but over time, like 2-3 hours, eventually all read within a degree of each other. 

Follow your iGrill, note the grate placement and lid therm readings, and learn the quirks of your WSM.


----------

