LG gas dryer not maintaining heat

[smaring]

Model Number: DLGX4501B
Brand: LG
Age: 1-5 years

I picked up this unit second-hand for a couple hundred bucks. When I went to do the gas conversion from natural to L.P. I realized the prior owners never cleaned the lint filter. I gave it a massive cleaning to ensure there were no more airflow blockages.

I replaced the nozzle on the gas valve to the L.P. nozzle and closed down the valve screw.

After assembly, however, the "cool down stage" light never goes off and nothing ever seems to heat and dry.

The "test cycle" shows "23" for a while and then "gas".

When I remove the door, leaving the latch sensor plugged in, and start a normal cycle I can see the igniter glow hot, the gas valve opens, and a flame is ignited for no more than 10 seconds before shutting off. A couple minutes later it will ignite again for no more than 5 seconds. I do measure resistance on the thermostats. I went ahead and replaced the high-limit thermostat thinking that perhaps it was too sensitive. It didn't help.

I understand that the behavior of the system will change as a result of air pressure and flow with the door and the top on. However, with those in place I've no way to see what the flame is doing.

I've considered picking up a manometer and testing the inches of w.c. on the gas valve as it is running. I've seen it suggested that other gas valves should be running at around 3.5" w.c.. However, I can't find any specs for L.P. running on this CGV22CK valve to even confirm that is the expected reading.

Any suggestions to help diagnose this would be greatly appreciated.

-Steve
Titusville, FL

[Doc Ryan]

Hi Steve,

The symptoms that you are describing are commonly caused by a failure of the gas coils on the gas valve assembly. On this gas valve, those coils are not available separately and are only sold as part of the gas valve assembly. Let me know what you find.

Gas Valve Assembly - AGM30063309 (PD00079483)

[smaring]

Thanks Ryan. That was my suspicion. I just didn't want to throw $200+ dollars at a possible fix without being a bit more sure I had ruled out all the other cheaper stuff. I'll probably order a new valve after my next paycheck at the end of the week. I'll report back if it managed to resolve the issue.

[Doc Ryan]

Sounds good!

[smaring]

I put a new valve in. I tried it with the door off and everything was great! It ran for quite a bit longer on the initial light. So, I slapped everything back together and started another cycle. No heat. I took the top off again, but kept the door on. I grabbed my automotive endoscope and positioned the camera down the side of the tumbler looking directly at where the flame ignites from the ignitor. Sure enough, with the door on, it does not ignite the gas. I removed the door again and measured 8" H2O on the screw port on the front of the valve while operating. I figured that seemed a reasonable amount of back-pressure from the nozzle being fed 10" H2O from the source, but I don't know for sure.

Considering no changes are being made with respect to connections the only possible difference is airflow. I can only imagine that I either need more pressure or less.

Something else worth noting: as you can see in the video here, several seconds after the flame ignites it also ignites all the way back up the tube to the nozzle.

https://drive.google.com/file/d/1PH6...ew?usp=sharing

[smaring]

I came up with a redneck idea. I duct taped the door area closed so that I could leave the door off to observe what happens when the blower sucks the gas down the tube. Sure enough, the gas flows, but it DOES NOT ignite. I'm reading 11.15" WC on the output of the second stage regulator and 7.7" WC on the output of the dryer gas valve. If I am to believe what Google AI tells me about the LP pressures on a gas dryer one would assume that to be sufficient. Perhaps not though.



https://drive.google.com/file/d/1PeK...ew?usp=sharing

[smaring]

From my shutoff valve after the second stage regulator I was using the 72" x 5/8" OD flex hose that came with the unit when I bought it second-hand. I had noticed that one of the ends was a bit kinked. I straightened it the best I could. I just took the hose off to check the flow for any potential blockage. A surprising observation, which I doubt is normal, is that it whistles when I blow through it. Loudly whistles actually. I also read the label on the hose that says to never re-use for another installation. I've ordered a new 72" x 1" OD flex hose. It'll show up in about a week. I'm hoping that will give me a higher pressure than 7.7 WC on the gas valve output and actually ignite the flame.

I tried to heat the blue loctite to move the nut in hopes of opening the valve a bit more, but it quickly became obvious that I would destroy the plastic before the nut would budge. It is apparent that was never meant to move.

[Doc Ryan]

If you look at the igniter, does it have any white building on the gray bar that glows? I wonder if the igniter is getting weak. Sometimes as the igniter gets older, it will not get hot enough to safely open the gas valves when it is time to light the flame. Sometimes a clamp on style amp meter is used to measure the amp draw of the igniter to see if it is good or bad.

LG Gas Dryer Igniter - 5318EL3001A (PD00001782)

[smaring]

I installed the 72" x 1" OD hose. It did not help. I installed a new igniter. I didn't help. I found that if I drove the adjustment screw down more on the gas valve that I could get it to ignite with the door opening sealed. However, it still won't ignite with the front door cover on. In a fit of desperation I even cut a hole in the side panel to allow some air in with hopes that would help it ignite with the front cover on. It didn't help either. This has become a very aggravating and frustrating fix.

Question: is it normal for the igniter to turn off before the gas valve opens? It seems odd to me that the igniter is already cooling down by the time the gas hits it.

[Doc Ryan]

Question: is it normal for the igniter to turn off before the gas valve opens? It seems odd to me that the igniter is already cooling down by the time the gas hits it.

No, that is not normal. Does the flame sensor have continuity at room temperature? Also, is the flame sensor dirty?

[smaring]

I do get a reading on the flame sensor and it didn't really seem dirty. I wiped it off anyway.

I paid more attention this time. It seems like the ignitor shuts off at about the same time the gas valve opens.

Here it is again igniting the flame properly with the front cover off:

https://drive.google.com/file/d/1Xpa...ew?usp=sharing

Here are (2) attempts (where it does not ignite) with the door cover on looking through the hole in the side I cut out:

https://drive.google.com/file/d/1XnJ...ew?usp=sharing
https://drive.google.com/file/d/1Xig...ew?usp=sharing

[Doc Ryan]

I wonder if the main control board is intermittently sending power to the ignitor. If you can find the relay on the main control board that sends power to the ignitor, you could try tapping on it with the handle of an insulated screwdriver. This will sometimes cause the relay to work temporarily and help you narrow down the problem.

Try these troubleshooting steps below:

[smaring]

I took a break from this project for a few weeks. Here's how the valve test panned out:

valve 1 (bottom): 103.6V during operation; 1.93 kOhms while off
valve 2 (top): 93V during operation; 1.84 kOhms while off

I'm still in the situation where the flame ignites with the door off, but not on.

From https://drive.google.com/file/d/1PH6...ew?usp=sharing

you can see that the flame ignites back up the tube to the nozzle. That doesn't seem like normal behavior. Could that be dangerous? What could the causes of that be? Lack of gas flow? The second stage regulator which is only driving this appliance is https://a.co/d/aflBJjU and the output port reads 11.15" WC. I wonder if these things have some sort of flow restricter that I missed. The hose is upgraded to a 1".

[Doc Ryan]

I am not sure if that is dangerous. It doesn't look safe to me.

If the output gas flow is inconsistent or varying, it could potentially cause this issue.

Have you done a voltage test while the issue occurs to see the voltage drops at all when it acts up?

Have you tried running the dryer temporarily with the exhaust vent removed to see if that helps? The flame should get sucked in towards the back of the dryer by negative air pressure created by the dryer. In your video it doesn't look like the flame is getting sucked in as much as it should. I could be wrong, sometimes it's hard to tell from a video.

[smaring]

Played with this beast again this weekend ...

I tried it with the vent tube disconnected. It didn't ignite. I put my hand on the vent port and confirmed that it is moving a lot of air.

The only time is doesn't ignite is when the door is on. So, checking for any voltage fluctuation when it doesn't ignite is difficult. I saw only very minor voltage fluctuation during operation with the cover off while igniting.

I did try with the door and top on (something I didn't bother with before since it wouldn't ignite with just the door on). I would then cover the access port I cut on the side to ensure the suction pull of gas to the back to be as expected. After hearing the gas valve open I would slide my cover away and confirm that it did not ignite.

I picked up a cheap flow meter. I removed the gas valve and hooked the flow meter to the pipe going into the valve. I measured 11.5 LPM. My Emerson-Fisher second stage is rated for an output of 29.3 SCMH / 13.8 LPM. I figured the small drop was a reasonable expectation for the 72" hose and bends and such. I would think 11.5 LPM ought to be enough volume for the appliance.



I considered trying something for a moment. That being switching back to the natural gas nozzle. That's when I noticed something that perked an eyebrow ...



The original nozzle that I pulled out is labeled N-CU LNG. The nozzle I replaced it with says P-CK LPG. I did some looking around and found people selling both the P-CK LPG that I got and another one labelled P-CU LPG as the same part number. That got me wondering if there might be a difference between the P-CK and P-CU and whether I'd have better results swapping the N-CU for the P-CU. Do you know if there's a difference?

[smaring]

Thanks for all the suggestions Ryan. I am throwing in the towel on this one and admitting defeat. Maybe it is a design defect or something. I know this model was not long on the market.

My old lady met the end of her patience last night. She's been hanging clothes to dry for nearly (4) months and has had enough. This experience, including the understanding of how gas dryers operate, has left her distrusting ALL gas dryers. So we went ahead and took advantage of a coupon for Home Depot and ordered the LG 9.0 cu. ft. electric that pairs with her washer.

I'm gonna scrap this guy for the gas parts, motors, blower, door, and a bit of sheet metal. I realized how good this metal was when I cut into it.

Cheers again for trying to help. Parts Dr is always my goto place when I need parts. You guys have never done me wrong and most repair jobs end up well. Can't win them all I guess.

[Doc Ryan]

Thanks for the update. I am sorry this repair didn't work out for you.