weber...

I don't rely on the Weber thermometer. I have used my Maverick ET-732 to monitor the grill in the past and I just purchased the BBQ Guru DigiQ-DZ2 to give me even more control over my temps. But, if you know that it is 10 degrees cold you can always just add 10 to it. I would assume, though, that the temp at the grates may be different than at the top.
 

thermoworks sez boiling water is not as accurate as an ice bath its what i use.

http://www.thermoworks.com/learning/thermapen101_creating_an_icebath.html

Analog bi metal thermometers are ONLY a bench mark to go off of.   My new "man law" thermometer is off 10-15 degrees from my Maverick,,, when my thermometer reads say 225 degrees then i know my actual real temp is 235-240 degrees.  

Use your accurate thermometers to calibrate the non accurate.  It's all good!

Drew,

What is you elevation above sea level (I know you are "Jersey" Drew, but that does not mean you are there now, which is why I asked).  Water boils at lower temps at higher elevations.  The higher you go the lower it boils.  In Denver, the boiling point of water is 203* instead of 212.  So depending on where you are, the thermometer may not be as off as you thought (either of them).

Water freezes at 32*F or 0*C regardless of altitude so that is why it's a better measure of a good thermometer.  I use both as one that is spot on a freezing may be off the higher the temp goes (and the inverse is also true).

Here is a chart of the temp water boils for a given altitude.

dward51 said:

Drew,

What is you elevation above sea level (I know you are "Jersey" Drew, but that does not mean you are there now, which is why I asked).  Water boils at lower temps at higher elevations.  The higher you go the lower it boils.  In Denver, the boiling point of water is 203* instead of 212.  So depending on where you are, the thermometer may not be as off as you thought (either of them).

Water freezes at 32*F or 0*C regardless of altitude so that is why it's a better measure of a good thermometer.  I use both as one that is spot on a freezing may be off the higher the temp goes (and the inverse is also true).

Here is a chart of the temp water boils for a given altitude.

Altitude compared to Sea Level​	Boiling Point
(ft)​	(m)​	([sup]o[/sup]F)​	([sup]o[/sup]C)​
0​	0​	212.0​	100.0​
500​	152​	211.0​	99.5​
1000​	305​	210.1​	98.9​
1500​	457​	209.1​	98.4​
2000​	610​	208.1​	97.8​
2500​	762​	207.2​	97.3​
3000​	914​	206.2​	96.8​
3500​	1067​	205.3​	96.3​
4000​	1219​	204.3​	95.7​
4500​	1372​	203.4​	95.2​
5000​	1524​	202.4​	94.7​
5500​	1676​	201.5​	94.2​
6000​	1829​	200.6​	93.6​
6500​	1981​	199.6​	93.1​
7000​	2134​	198.7​	92.6​
7500​	2286​	197.8​	92.1​
8000​	2438​	196.9​	91.6​
8500​	2591​	196.0​	91.1​
9000​	2743​	195.0​	90.6​
9500​	2896​	194.1​	90.1​
10000​	3048​	193.2​	89.6​

Click to expand...

So, in order for him to get a temp for boiling water of 10 degrees cooler he has to be sitting on a mountain top like a BBQ Guru. :D

The best thing to do is get an accurate therm (or two), drill a 1/4" hole thru a small block of wood place and place the therm thru the hole. Fire up your smoker, place the block(s) on each rack and adjust your smoker till the accurate therm reads 250°. Then note the temp shown on the Weber lid therm, from then on you can use your lid therm as a rough rule of thumb as long as you keep the temp differance between the two therms in mind.

Example: If the lower rack was at 250° and the lid read 225° you just know to add 25° to a lid reading. This way you can use the lid therm to watch for spikes and to make sure you are in the general area you want to be in, while using the probes in the meat.

Ok, just wanted to make sure you were not in Denver or some other high altitude location.  Sounds like the Weber is Kaput....

I have an older style WSM and it did not have a thermometer mounting hole. I had to drill my own and added a nice commercial Tel-Tru thermometer to mine.  How do the new ones mount the thermometer?  Is it a threaded hole or a friction fit type thing?  Can you post a photo of how it mounts and how far into the dome the probe tip protrudes.  I have an ideal, but wanted to see what the stock set up looks like first.

I'm hoping it's a threaded setup, even if it's a small threaded opening.  If it is, I'm thinking you can make an adapter and use a Tel-Tru with a little longer probe (to allow for the spacing of the adapter). I have a model GT-300 (3" face) on my WSM.  It has 1/2" NPT threads on the stainless body.  I'm thinking you could find brass adapters (might take 2 or more) to step from 1/2" NPT to a different size as long as there was still room for the thermometer stem to make it though the center of the smallest adapter.

Of course there is always plan "B".  Chuck the stock one, get a step drill and drill a 1/2" hole for a Tel-Tru.  Probably more accurate, cheaper in the long run, and better quality than shipping back and forth to Weber until you get one that works well enough.

Here is a photo of mine.  It's pretty dang accurate too.  Got it on E-bay for around $25 in new condition.  I liked this temp range, but they have a lot of options on temp range, stem length, recalibration, etc...