Gas Dryer flame dies

[KTM 525EXC]

The flame on my 2007 LG Gas Dryer model DLG8388WM is not staying lit. It fires up OK after a minute and begins to heat, but then goes out. The dryer continues to run, and you can smell unburned gas coming out the exhaust vent and in the drum when you open the door. It does this no matter what setting you use, manual time/temperature setting, or automatic dryness sensing mode, and in any temperature setting.

This thing is under warranty. I had Sears come out yesterday, they pulled it apart and could find nothing wrong, everything checked out OK. They buttoned it back up and told me I would have to open another service order, apparently they are limited to performing only basic diagnostics on the initial visit. Oh, and they also told me they don’t stock controller boards and sensors for these things, that’s a 10 day turn around. And that I could expect it wouldn’t get fixed until at least the 3rd visit.

I realize this is a DYI board, but I get the feeling I’m going to have to become an active participant in the troubleshooting, and suspect this is probably a common problem well understood by the moderators/users here. Hopefully someone can point me and my technician to the failed component.

Life is Good. But it was a lot better back when appliances had simple mechanical controls.

[JWWebster]

How long is your dryer vent run? How many turns are in it?

[KTM 525EXC]

The exhaust run is apx. 15’ with 4 90* bends mostly all HVAC type duct, with only a little flex tube coming off the dryer. The tech thinks the exhaust flow is OK.

[JWWebster]

That's the problem. From our friend John63: 
Inspect the dryer venting from the rear of the dryer to the outside vent hood of the home.
If there's a restriction in the vent--the clothing in the dryer takes longer to dry.
When the dryer is functioning normally---the time required to dry laundry is determined by the *Sensor* located on the drum side of the lint filter housing and by the main control board.
When laundry is near dry--any Time Remaining on the control panel that is *not* needed will be eliminated---except for the last 6 minutes.
The final 6 minutes of any automatic cycle is for cooling down the laundry before the dryer ends the cycle.
If a dryer *counts down* to the last 6 minutes but the laundry is still not dry--the computer will allow the dryer to run until the laundry has dried or defaults (not drying within the additional time allowed).
Dryer vents that are longer than 8 feet with more than (2) 90 degree turns--can affect drying performance.
Setting the DRY LEVEL selector to *Very Dry* will solve most dryability issues. In homes with abnormally long vents--even the longer run time in the *Very Dry* setting is usually not sufficient to dry laundry loads.
Reducing the length of the vent or starting a second cycle becomes necessary to fully dry the clothing.
If a second cycle was started---only the amount of time that is needed to dry laundry will be used before dropping to 6 minutes and then the cycle will end with dry laundry.

[KTM 525EXC]

Correct diagnosis, thank you. I dug into it and found the vent duct clogged. Seems the HVAC guy that installed the duct screwed the sections of the duct together using 1” self tapping sheet metal screws which protruded inside the duct; I guess that’s acceptable for HVAC duct work but for dryer vents those screws acted as lint traps inside the pipe. I scrapped that piping altogether and installed new 4” rigid aluminum, in a straight line to the outside vent hood. The exhaust flow seems 2 to 3 times stronger now, and the dryer works again. I’m a little surprised the technician didn’t diagnose this during his service call. So I guess this is a DIY after all.

Thanks again guys.