This question is in the top ten of fielded questions by Customer Service. There are many reasons this can happen. Below is a list of statements that we receive most often, with the associated reasoning and solutions.
1. When I start my cooker and set the temperature that I want to cook at, it goes into maintenance mode before it reaches my preferred set temperature and seems to take forever to get to the temperature I have set.
a. This is built into the programming of the controller to prevent temperature overshooting past the desired set temperature, during the initial heat up mode after startup. 10 minutes after hitting the START button, push and hold the START button to see the current "H" mode on the display. If the "H" mode is H1, then the cooker determines and anticipates when to go into maintenance to prevent overshooting the set temperature. It will "zero in" and get to the set temperature. Suggested reading: viewtopic.php?f=36&t=76
2. After I start my cooker and set my desired cooking temperature, it goes into maintenance mode when it hits my set temperature, but then goes to over 100 degrees past the set temperature.
a. This is designed into the controller. When you hit start, and set your desired cooking temperature, the controller starts calculating the difference between the current cooker temperature and the desired set cooking temperature. The desired outcome is to get the cooker up to temperature as quickly and efficiently as possible. To achieve this, the controller calculates the temperature differential and will "shift" into a more aggressive pellet feed rate as required. 10 minutes after hitting the START button, push and hold the START button to display the current "H" mode. If the "H" mode is H2 or H3, you can have up to a 100+ temperature overshoot from your desired set temperature. This is normal behavior, and the controller will "zero in" on your target temp around the 30 minute mark after you hit the START button. Suggested reading: viewtopic.php?f=36&t=76
3. When cooking, after I open the lid, the temperature drops way below my set temperature, and then shoots 50 or more degrees above my desired set temperature, after I close the lid.
a. When the cooker's lid is opened, the cooking environment collapses, the cooking process stops, heat is allowed to escape from inside the cooker and causes the metal mass of the cooker to start to cool. The programming of the controller has an "open lid" feature that will accelerate the temperature recovery. Depending on how much heat is lost, the controller determines how aggressive it needs to be to get things back on track. Depending on the chosen aggressiveness, the cooker temperature may rise past the desired set temperature, but it will "zero in" if allowed to do so. Suggested reading: viewtopic.php?f=36&t=76
4. After spraying/squirting/mopping, the meat I am cooking, the temperature plummets way below my desired set temperature, and takes a very long time before it starts to climb back toward where it needs to be, and then shoots way past it before it comes back down to where it needs to be.
a. In addition to #3 above, adding liquid to any cooker causes an additional "evaporative cooler" effect. This causes the cooker to drop further below the desired set temperature, to be very aggressive during the recovery process, and can take much longer to recover and stabilize at the desired set temperature. All of the added liquid must evaporate before the temperature can begin to stabilize, and allow the actual cooking process to recover and continue. Suggested reading: viewtopic.php?f=36&t=76
5. My cooker will not settle in at my desired temperature, so I have to constantly keep changing the set temperature to get it to get close to the temperature I want.
a. Here is a rule: NEVER change the set temperature on the cooker in this manner. Doing this "confuses" the controller and causes it to never be able to stabilize and "zero in" on any desired set temperature. The fire in the cooker is a wood fire, and achieving and maintaining a desired set temperature takes time, as feed rates are changed and pellets are added and burned. Think of this as a dance with your significant other. If the music constantly changes before a song ends, it can get very confusing to know what dance steps to do, and completely kills the mood and desire to dance at all. Suggested reading: viewtopic.php?f=36&t=76
If after reading the above, you still feel that you have a problem that is not addressed, please post your concerns, or send me an PM, and we will address them. If you want to verify that you cooker is working properly, you can do this test: viewtopic.php?f=36&t=80
- Joined: May 10th, 2014, 12:33 pm
- Posts: 576
- Location: Sitting Near a Yoder Smoker, Smelling Sweet Blue
Thanks for posting this great info, Herb. A look "under the hood" about the controller is very helpful to understand that some of the perceived "odd behaviors" of the controller are actually indicators that it is working properly.
A question for you. I just got my YS640 and I did the break in like the manual said. One thing I noticed was on the control panel it said 350, but on the duel thermometers on the hood only got to maybe 300. I then cleaned it and set it for 275 to cook some chicken and they are only reading 200. Is it normal to have that range of a temp difference?
- Joined: May 10th, 2014, 12:33 pm
- Posts: 576
- Location: Sitting Near a Yoder Smoker, Smelling Sweet Blue
Yes. The door thermometers are only a gauge, but are not accurate to where the important readings are taking place. On my YS640 they were anywhere between 50*-150* off based on how hot I was cooking. Don't worry about those being off compared to the controller, you unit is working fine.
Yoder_Kirby thanks for the info. Guess they are really for looks they anything useful. Being off that much is of no value for trying to control temps.
- Joined: May 10th, 2014, 12:33 pm
- Posts: 576
- Location: Sitting Near a Yoder Smoker, Smelling Sweet Blue
They can still serve a purpose. If you have two, you can see what the approximate deviation is from the left side to the right side of the top shelf. Or if they are the same temp, you know it's running even on the top shelf. It's not an everyday type of device, but it is nice to have if I want to know what is going on inside on the top shelf sometimes. They aren't for everyone, but you can learn how to use them to help guide you. You will learn how with time and use of the pit.
Mine is the total opposite of number 1. I smoke at 225. I set it to 225, it runs up to 275 or 300 before going into maintenance mode. Takes leaving the lid open for a minute or 3 to get the temp back down. I also do not suffer from number 3 too much. Which I really like while wrapping ribs and shifting meat around in the cooker. With that said, this thing works perfectly. Couldn't ask for more in a wood fired pit.
Blown UDS
PK
Official Beer Taster
Smoke-a-holic
While they may be off from what the grate temperature is, you can still utilize them to know what the grate temp is in the cooker. With my big trailered cooker, I know that when my grate temp is 235 my door therm should read right at 200. So, knowing this I can easily tell if my cooker is where I want it to be without opening the door of the cooker. You just need to map the grate temps in your cooker and see how they coincide to the door therms.
Eagle River Barbecue
YS640 Comp Cart
Stumps Platinum 5
My issue is always heat variation from side to side on my YS640, which is known to Yoder and other 640 owners. If there's a mod that I'm not aware of that addresses this issue please let us know. I have just learned to "manage" it by using instant read thermometers, moving smaller food around in the smoker to hotter and cooler sections, or by putting thicker ends of meat (brisket point ends in particular) towards the hotter chimney side of the grates. I know there was some discussion a few years back of extending the metal drip tray to create a smaller gap near the chimney but don't know if this was ever done. Herb or others, any recent insights on this question? Many thanks in advance for any help/suggestions. It honestly hasn't diminished my enjoyment of the YS640, nor my pride in recommending it, as all smokers have some tweaks that make them work as the owner wants. Just want to put that out there so nobody misunderstands where I'm coming from. Think it's a great product but just curious if there's any current efforts to address the one idiosyncrasy of the 640 that I'm aware of. The other cool feature I'd love to see is a wireless remote low pellet alarm that could talk to an app on my iPhone so I can avoid those few times when I forget to refill the hopper before it's too late! 
Here are the common things that affect the side to side grate temperatures:
1. Check that the burn grate is fitting properly in the fire box.
2. Make sure that the chimney is flush with the inside wall of the cooker...it should not protrude into the cooking chamber.
3. If foil is being used in the cooker, it should not restrict the air flow under or around the diffuser plate. Do not foil the grease channel. Try a temp test with no foil in the cooker.
4. Be sure the diffuser plate is centered front to back.
5. Do not run temp probes into the cooker through the door. The cooker door needs to stay sealed because of the positive air flow in the cooker.
6. If measuring temperatures beyond the diffuser plate on the right side, move the probe at least an inch to the left of the end of the diffuser plate. The right side will be hotter because of the chimney exhaust.
7. A good starting point for the sliding damper is to pull it all the way out to the right, and then back in to the left about 5" or 6". Then adjust from there.
Lengthening the diffuser plate would make it that much harder to remove from the cooker, and the effect was minimal.
If you cooker has a manufacturing date prior to May of 2013, there is a fan diffuser update that greatly improves the grate temperatures and pellet consumption.
The current revision of firmware is u26 for the YS640.
I hope this information helps to address your concerns.
It does Herb, many thanks. Yoder did send me the fan diffuser update but I have yet to install it, so I'll do that and hope for the best.
Thanks!
TJ
Did the install yesterday and posted same question in FAQ's section of board. The installation was extremely easy to do and took no more than 15 mins from start to finish. Haven't run it yet w/ diffuser but hope to soon. The diffuser obviously redirects air flow from the fan closest to the outside of the pellet hopper, but I'm just curious how this modification could impact side to side temps and pellet consumption? I'm not questioning whether it works, just how.
Thanks,
TJ
TennesseeJed wrote:Did the install yesterday and posted same question in FAQ's section of board. The installation was extremely easy to do and took no more than 15 mins from start to finish. Haven't run it yet w/ diffuser but hope to soon. The diffuser obviously redirects air flow from the fan closest to the outside of the pellet hopper, but I'm just curious how this modification could impact side to side temps and pellet consumption? I'm not questioning whether it works, just how.
Thanks,
TJ
Update 9/1/14. Ran my 640 yesterday with BBQr's Delight pellets (hickory, fwiw) after completing the fan upgrade last week. It was fairly hot here so I'm not really sure it was the best test environment, but I can definitely say that I used less pellets than I would have expected prior to the modification. I cooked 4 racks of baby backs and a full hotel style turkey breast. After re-reading Herb's post, I also checked each of the items on his recommended temp variations fixes and noticed that the smokestack/chimney on my 640 had eased its way into the cooker a bit and was protruding into the smoker by about 1/2". I hadn't even checked this for over a year. Not sure if it just moves on its own a bit w/ temps, or if I bumped it while cooking or moving it at some point, but the chimney had definitely drifted in a bit beyond flush. Worth checking regularly on your 640 just to make sure it's flush...
640 ran like a dream yesterday and, while I did not check w/ thermometers to be absolutely certain of the side to side temps, I did not notice much of a difference in doneness in ribs from side to side.
Thanks again Herb for the great tips!
For What It's Worth... Check my post on the "Questions about the Smoke Stack"... to help keep the stack where I want it. I was having the same problem. 
Update 2, 9/16/14: I have run the 640 a few times now for a few different cooks and I am definitely noticing a difference in pellet consumption. I have not been scientific about it at all, but I am getting much better burn rates w/ the diffuser added. For all you older YS640 owners who haven't completed the fan diffuser update, I would highly recommend it!
Thanks again to Yoder!
how do i check to see if my 640 has had the update. I bought it second hand and would like to make sure my firmware is the latest and greatest.
- Joined: May 10th, 2014, 12:33 pm
- Posts: 576
- Location: Sitting Near a Yoder Smoker, Smelling Sweet Blue
When you turn it on the cooker, then controller will display "U26" or some other number after the "U" after you press start. U26 is the most current YS640 program.
Thanks Kirby. I need the upgrade it seems. How do i go about getting it and what does it entail. I may not be smart but i can lift heavy things.
- Joined: May 10th, 2014, 12:33 pm
- Posts: 576
- Location: Sitting Near a Yoder Smoker, Smelling Sweet Blue
If you unit is working to your liking, you don't HAVE to update. However if you want to, I understand.
It's a fairly simple procedure in which all you do is remove the hopper side panel, unscrew the controller and plug in an updater that's done in about 10 seconds. Contact Yoder customer service to get your name added to the updater list.
i have a YS1500 and i see a lot of smoke escaping from my hatch when it is shut. The temperature variation on the hopper end vs. the other end is 40 to 50 degrees. I am not sure the hatch fits properly and not sure what to do about it.
How long have you had your cooker? How many times have you cooked on it?
The metal in the cooker when new, has not been "cured". When you cook, the metal heats up, and when you are done it cools down. The more times this happens, the less and less the metal will expand and contract, which is the "curing" process. During the curing process, the metal will start to fit tighter and tighter together. Also, the more times you cook on it, the more seasoning will build up on the inside of the cooker surface, which will naturally block the leaks from the cooker even more. The cooker was not designed to be "sealed".
On the 1500, you can open the fire damper to compensate for the temperatures across the grate surface.
I have owned the smoker since April or May of 2014. I have cooked on it 10 times and the issue has been there since day one. i can trey the fire damper but i am worried the door was bent in shipping or something. I can send you pictures next time i use it. it just seems like 50 degree difference from one end to the other is pretty big. I use my own thermometers to test the temps. Thanks
attached are two photos showing the gap. One photo shows a side view of the gap with the hatch closed as tight as it will go and the other picture shows the discoloration of where the smoke is escaping. The color is darker where the smoke is escaping. Thanks
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yoder herb, can you please respond to the above post. thank you very much
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