Joe Traeger developed the Traeger pellet grill in 1985 and patented it in 1986. Early Traeger Grills, as well as many of the pellet grills first introduced after the expiration of the Traeger patent, used a three-position controller, called an LMH controller indicating settings for low, medium and high heat. Each setting approximates a temperature range, and those temperatures were achieved by means of a fixed, predetermined duty cycle. Furthermore, because the duty cycles are fixed, they don't account for weather conditions or the amount of food being cooked, both of which affect temperature.

Gas Grill Troubleshooting

Unusual Temperature Swings 
It is totally normal for the temperature inside your Traeger pellet grill to vary by as much as 15-20F above or below the target you’ve set. That’s all part of the regular cycling on and off of the auger and the rod. When it cools down inside, more pellets feed in and ignite. When it’s too warm, they stop for a bit. 
It’s important to remember that a temperature you set, is the target temperature that the grill aims for as an average over the entire time of cook! So 15f to 20f temperature swings are, according to the way it’s designed, perfectly natural. 
Any dramatic swings outside that range, however, may indicate a problem somewhere. But what? 
First, give some thought whether this might actually be perfectly normal. Remember, the 15-20F variance is an average across the entire cook under ideal conditions. If it’s really cold or really hot outside, your Traeger has to work hard to compensate. In such cases, you might find temperature swings outside that range that are not the fault of the grill itself. Do what you can to protect your grill from the elements to minimize the effects of the weather. 
If you’re sure it’s not the weather, a good first place to look is your fire pot. The fire pot was designed for a series of holes for optimal airflow. If new holes appear thanks to our old nemesis corrosion, you’ll get too much air and higher temperatures as a result. 
Speaking of corrosion, check the drip pan and the heat diffuser for damage. If there are less of these items than there should be, that could also lead to excess heat inside your Traeger. 
Your pellets are possible suspects, too. Low-grade pellets may produce a lot of ash. Not only can ash mess with the ventilation holes but also, if there’s enough of it floating around, it can lead to false readings from the probe. 
Try to use only quality pellets, such as those from our guide to the best pellets for pellet grills. 

No Pellets in the Fire Pot 
The automatic, rotating auger is supposed to pull pellets from the hopper to the fire pot when the controller says they’re needed. It’s an amazing system — unless it’s not working. 
The problem could be a purely mechanical one. From time to time, pellets may jam and prevent the auger from turning. To fix this problem, just clear out the auger tunnel. This will require you to disassemble the hopper and the auger, but it’s not really that hard, and you’ll need just a few basic tools.
The other possibility here is the motor is defective or damaged in some way. If there’s no obvious jam, you may need a new motor. Contact Traeger for assistance if you can’t get things working. 

Fire Goes Out in the Middle of a Cook 
There are several possible reasons for a fire to go out in a Traeger. Once again, we have to check the fire pot to see if the air holes are blocked. Fire needs oxygen to burn, and without those holes, there’s no oxygen. This is another time when the pellets may be the problem. Our recommendation: buy good pellets right out of the gate! 
A faulty connection with the probe or a bad reading could be the problem, also. If the controller is getting the wrong information, or none at all, it may not send enough pellets to the fire pot to keep the fire going. 
While you’d expect to see an error code, such as LEr, remember if you’ve got your temperature up to, say, 400F, it’ll be awhile before it drops below 125F, even without any fire. 
A third possibility is the fan. There’s a little fan in your Traeger that helps push oxygen over the fire pot to stoke the fire. If it’s not running for some reason, this could affect the ability to keep a fire burning. If you can hear the fan humming, you’re all good. If not, it is, yet again, time to call Traeger. 

Traeger Grill Not Lighting 
The power is on (this should be the first thing you check for any problem!), the auger is turning, the pellets are dropping in the fire pot — but nothing is lighting. Here’s an easy one to solve. 
The most likely answer here is the igniter isn’t working. Try running the grill with no pellets, and remove the heat diffuser, the drip pan, and the grates, so you can see right into the fire pot. The tip of the igniter should glow red. If not, there’s your issue. You know what that means — call Traeger! 
It’s also possible this is a fan issue. If the fan isn’t working, there may not be enough oxygen in the environment for the pellets to catch. Listen for the hum of the fan motor to determine if it’s working. 

SOURCE: foodfirefriends.com