My clothes dryer doesn't stay hot for long

November 8, 2007 10:34 AM

My gas fueled clothes dryer initially gets hot but soon after goes cold...hivemind help me debug the problem.

I have a Frigidaire gas powered clothes dryer (model #FDG336RES1) that I inherited with my house. Within the last week or so, the dryer has failed to dry any clothes. I have thoroughly cleaned out the lint in the exhaust, from under the motor and from the front of the dryer (Much thanks to previous AskMefi Q&A's for pointing me to a resource that told me how to open up my dryer for closer explanation).

With the front off, I can examine the behavior more closely. Here's what happens:

1.) The drum does turn appropriately
2.) The igniter glows orange
3.) The gas fires and an impressive blue flame is produced
4.) The flame burns for about 90 seconds and then goes out.
5.) Later, the igniter will glow orange again (and I hear the clanking or clacking noise...before I opened it I thought this might have been a slowly failing ball bearing but the noise reappears only when the ignitor is trying to do its job) but no flame (and this step will repeat).

I am stuck at why the flame ignites once per cycle but doesn't go again. I can stop the cycle after the flame goes out and then restart it and it will burn for the aforementioned 90 seconds.

I'm kinda at a loss at what the problem would be. Gas coils? the igniter? the thermostat? the safety thermostat? something else?

All the guides I have seen on troubleshooting the problem give different symptoms then what I am seeing since it initially works but then stops.

Can the Green help me be green (repair rather than throwaway) and save some green (replacement parts vs. a new dryer)? Thanks.

posted by mmascolino to home & garden (13 comments total)

There's a part which checks that the flame is burning. (Sorry, no name comes to mind, and I don't know your dryer, but iirc it's a metal tube.) It sounds like that's the part which needs replacement -- when it thinks there's no flame, it shuts off the gas. No idea if you can replace that part alone, or if it's built into the rest of the controls, but I'd guess it's replaceable.
posted by anadem at 10:51 AM on November 8, 2007

Thermocouple, replaceable
posted by mrleec at 10:55 AM on November 8, 2007

seconding mrleec.
posted by notsnot at 11:05 AM on November 8, 2007

Interesting...is it possible for a termocouple to work once per cycle and then fail? Does a dryer do something different on startup like bypass the thermocouple?
posted by mmascolino at 11:05 AM on November 8, 2007

Have you checked that the vent is unobstructed?
posted by winston at 11:33 AM on November 8, 2007

That is, you say you've cleaned the lint out of various parts of the dryer -- did you continue all the way down the tube to where-ever it vents outside?
posted by winston at 11:34 AM on November 8, 2007

winston: Yes, i did that as well.
posted by mmascolino at 11:41 AM on November 8, 2007

is it possible for a thermocouple to work once per cycle and then fail?

Sounds like the thermocouple is not working at all. Here's what typically happens...

1) You start the dryer
2) Controller within the dryer applies power to the igniter
3) Controller opens the gas valve
4) Controller waits a little while and then checks to see if it's getting a signal from the thermocouple indicating heat
5a) If it is, then continue...
5b) If not, then shut off the gas.

The controller is checking the thermocouple signal to make sure that the gas is burning. If the gas isn't burning (say because the igniter has failed) then it shuts off the gas to prevent a buildup that might explode.

Since you know that the burner is burning, it's very likely that the thermocouple has failed, thus the controller thinks that there's been no ignition and shuts off the gas.

Recycling the dryer starts the whole thing over again.

(This is a similar failure to one I had on my furnace several years ago, during one of the coldest days that January. Brrrr)
posted by johnvaljohn at 11:50 AM on November 8, 2007

Well thanks johnvaljohn, my understanding of how the thermocouple worked was backwards...I thought it had to sense heat (in this case from the igniter) before it opened the gas valve.

One other thing, I just got off the phone with an appliance parts company and they never heard of a thermocouple in a gas dryer....do the gas dryer world use a different term or is ther thermocouple embedded in another part or did I just deal with an unhelpful person?
posted by mmascolino at 12:26 PM on November 8, 2007

Either it's time to find a new parts supplier or you had an extremely unhelpful and ignorant employee @ your "appliance parts company."

See the wikipedia article on Thermocouples

Alternatively, you might have been asking advice from someone who takes orders; if that's the case I suggest you find a local supplier who can also offer some advice and hand-holding on what--although it is a simple procedure it involves fire and therefore very risky to your house and all of its contents to say nothing of the occupants of the house viz., your spouse, your kids, your pets, and your relationships to the same. Your spouse is likely to get upset if you set the dryer or the house alight.

You should be able to find an experienced repair person @ the local parts supplier who has performed this procedure infinitely more times than you.
posted by dan21 at 12:53 PM on November 8, 2007

Indeed...I've clearly done this zero times. I may have well been talking to an order taker. However to play devil's advocate, I just found the parts manual (PDF) and it doesn't have any part labeled as "thermocouple". The position of the nebulously named "Sensor" (part #79 on page 10) would suggest that it has the same purpose as a thermocouple but I'd rather be a little bit more confident about it being the problem before driving halfway across the city to a place that sells the parts.
posted by mmascolino at 1:33 PM on November 8, 2007

The likely culprit is the sensor, part number 79 in the parts manual. It is attached to the burner tube with a single sheet metal screw that you can easily remove. The gas valve harness #55 is plugged into it. Just unplug the harness from the sensor and replace it. It shouldn't take you more than five minutes, assuming you can get easy access. The parts person is correct. This is not a thermocouple but instead a different type of temperature sensor, but serves the same purpose. It detects if there is a flame when the gas it turned on. If not, it turns off the gas. If the sensor fails, it is unable to detect the flame so turns off the gas.
posted by JackFlash at 2:34 PM on November 8, 2007

Thanks for the explanation JackFlash that makes sense. Let's just hope that I have easy access to remove that screw without taking the whole tub out. :-)
posted by mmascolino at 2:43 PM on November 8, 2007