Gas Dryer Not Heating

by Mark
(CA)

Appreciate some help re. testing my gas dryer radiant/flame sensor,

Whirlpool/FSP P/N 338906. My understanding is that it should be closed circuit when no light shining on the window, and open-circuit with light. Mine worked that way at first, but after I shined my 75 watt trouble light on it for a while, when I remove the light and put black tape over the window, it goes closed circuit?, BUT when I now shine my trouble light on it, it WON?T go open circuit even after several minutes. Did I zap it? How much light should be used to test it? Testing done out of dryer.




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Answer


Hi Mark,

This is Shawn creator of www.applianci-repair-it.com. I have never used a trouble light but this is how I would test a gas dryer. Start the dryer and watch the igniter. The igniter should glow red for some time (30-120 seconds or so) then the igniter will go out and the flame should ignite instantly. If the igniter doesn't glow red use an ohmmeter to check for continuity across the igniter with the dryer unplugged and the igniter disconnected. If the igniter checks ok check the thermo fuse located on the duct in the back compartment it should have continuity across it. If the igniter glows but after a few minutes doesn't go out the flame sensor is bad (the part you are describing above). If the igniter glows and then goes out the coils on the gas valve are most likely bad. Also if the dryer is heating intermittingly it is most likely the coils on the gas valve. All of this and more are on this page
Gas Dryer Repair
Thank you,
Shawn/admin

Hi Shawn,

I want to THANK YOU and a couple other folks whose Internet sites I've used to learn how my gas dryer works, which has allowed me to repair it. Its ACTUAL PROBLEM was that one of the gas valve coils would go "open circuit" when the dryer got hot. I probably would not have known to test the coil resistance WHILE HEATING IT with a heat gun, had I not been pointed to the probability of bad coils in various Internet sites.
However, while I had it a part, I figured I should test and consider replacing any related component that might be bad or suspect, which is why I tested the Flame Sensor. UNFORTUNATELY, one site that talked about the Flame Sensor, said that it would switch (to open circuit) if/when you shine a flashlight on it. Mine would NOT switch using a flashlight, or even with my 75 watt incandescent trouble light shining on it, so I thought it might be bad too. Fortunately, a different Internet site NOW informs me that it takes HEAT from the igniter to cause the Flame Sensor to switch, so I went ahead and installed my (suspect) Flame Sensor, and it has been WORKING FINE through about 6 dryer loads today. Again, THANK YOU for your time to answer my e-mail, AND ALSO for putting your nice website together. I have book-marked it, and will share it with friends.

Sincerely,

Mark


Hi again Shawn,



I actually wasted a moderate amount of time trying to check the flame sensor per the erroneous instructions (aka flashlight). Also, the following websites gave resistance specs for these coils, but my
BRAND NEW FSP ones were technically out of spec, as the 1->2 resistance I measured with my name brand digital ohm meter is 1415 (vs. 1365 +/- 25) and the 1->3 resistance measured was 590 (vs. 560 +/- 25) and the resistance across the 2 wire coil was 1298 (vs. 1220 +/- 50), but what was I going to do, as had to get the unit running before the family "killed me". Do you have any comment as to the resistance values/specs? FYI, I used the heat gun, because my problem was intermittent, and with my newer style Whirlpool dryer (which does NOT have the ~8" high access panel across the front bottom like my old one did), I was not able to make measurements with the unit running and not heating. Was glad to see the coil go "open circuit", but then as say, got mislead re. possible bad flame sensor.

THANKS AGAIN FOR YOUR TIME AND HELP!
Answer

You are welcome! Glad to hear you got it working!! I have never heard (nor do I believe) that you could shine a light on the flame sensor to get it to work. It works from the heat off the igniter. That was a very good idea to test the coils while heating them with a heat gun. I usually don't test them at all because they have a tendency to intermittently check good or bad. Those coils consistency give false positive readings so I just replace them for three reasons; one if the igniter goes out but the flame doesn't light, if it heats sometimes and sometimes it doesn't or it starts heating then quits. These scenarios are almost always the coils. With that being said I love your test with the heat gun it will confirm that they are bad.

As for the resistance value I wouldn’t worry about it especially if the dryer is working now! I try not to get caught up in things like resistance values and things like that especially on my website. I try to keep thing as simple as possible on most things 99% of the time if it is not an open circuit the device you are testing is ok. However this isn’t true all the time. I normally don’t even test for ohms across these coils I just check it as I describe in both of my other e-mails because I found them to test very inconsistent.

As for you spending more time on the repair as you should I think that it is ok because you managed to repair it yourself which is what you set out to do! I wouldn’t have spent a lot of time on the flame sensor simply because I understand how they work and I know they give very little trouble. I am not sure where they came up with the idea that shining a flashlight on it would work I would think it would have to be a hot light then again I never tried it. I would have to see it to believe it. In any case I am glad that you got it repaired

Thank you
Shawn/ Admin

Comments for Gas Dryer Not Heating

Click here to add your own comments

light sensor for gas dryer
by: steven

i wont to ask can you short the wires that are going to the light sensor to test if it is good.
Re
by: Shawn

Hi Steven,

I don’t recommend it. Describe what it is doing and I will try to help!
gas dryer
by: steven

hi,the gas dryer works at the first time good when you gonna use it and dries the clothes good when you use it the second time it will not dry the clothes and it is brand:frigidair . i measure the two valve and they give me diffrent omhs. i think they are good i try to measure the light sensor it measure closed and i put a ligther on it to see if it opens but it would not open thats why i ask if you can short the two wires who are on the light sensor ,i think the working of a lightsensor is like a light sensor it works like a switch.the igniter measured 53 ohms thats why i thtink it is the ligtsensor.

thank you,
STEVEN
RE
by: Shawn

If it is intermittently heating/not heating most likely the coils on the gas valve are bad regardless of how they ohm out.

Shinning a light on the flame sensor will not have any effect on it unless it is a very hot light. It is closed to begin with then when it gets hot from the igniter it opens; when it opens current is diverted from the igniter to the gas valve coils. Flame sensors very seldom go bad and I personally have never seen an intermittently bad flame sensor. Not to say it is impossible.
Confused
by: Robert

Shawn- I have a Therm-O-Disc Sensor in front of me that tests closed while cold. Both sensors read 1300+ ohms. I replaced the Ignitor. I think I should replace the Sensor too. What do you think??
RE
by: Shawn/admin

I am assuming you are referring to the heat sensor on the side of the heater can.

You can?t really know for sure if the sensor is bad unless the igniter will glow orange but never go out. If you can?t see the burner box when the dryer is on typically you can place a mirror under the dryer on the same side as the burner box to see if the igniter is glowing or not.

What should happen is the igniter will glow for about 15-30 seconds then the sensor detects heat off the igniter and opens up. Once the sensor opens power is diverted from the igniter to the gas valve coils. Therefore the igniter should stop glowing and the flame should light simultaneously. If the igniter stops glowing but the flame doesn?t light then the coils on the gas valve are usually the problem. If the igniter continues to glow and never turns off the sensor is bad. If the igniter will not glow then the igniter is typically bad but it can be a safety thermostat or the timer. Whirlpool dryers have a fuse that turns off the heating system in the event it overheats. More is explained here Gas Dryer No Heat
dryer not heating
by: Anonymous

My igniter is working fine and the coils ohm out correctly but not getting gas to the igniter. Could it still be the coils?
RE
by: Shawn/admin

The ohms across the coils is not necessarily an indication that they or good or bad because what often happens is they will work for a few times then once they heat up they fail. So yes it can still be the coils.
Want to take dryer to shooting range.
by: Will

Hi, Well here's the story... I have a new (Just out of warranty) GE gas dryer. It has always had noisy coils (like a tattoo gun in a coffee can) but has worked fine. The "Buzz" went away and no heat... So i put new coils in today and dried about 4 loads (the "buzz" only happened for .5-1sec when coil kicked on) and after 4 loads no heat no flame.

So I guess my question is.. can the dryer send too much Voltage and "burn-out" a new coil? can the valve it self be "sticky" and burn out coil?
P.S. when I removed 3 prong coil there was a "shim?" around valve stem is that normal?
RE
by: Shawn/admin

I wouldn’t think it was sending too much voltage to the coils. You may want to try the coils again or maybe even the whole gas valve. I don’t suggest messing with the gas valve unless you have experience working with gas and know how to check for gas leaks.
Changed solenoids and same symptoms
by: Russell

Hey Shawn, A while back I tried to fix my dryer with you tube videos. What I learned seems consistent with your comments, and I changed the solenoids. I still get the ignitor working properly, a click and then nothing. I guess the click is the flame sensor opening? The dryer is about 4 years old but has had very little use because we use a clothes line. Like you say, the gas valve should not be suspect. Anything else I can do?
I am wondering if the solenoids that I bought could be bad? Not likely though. Unfortunately, I have the dryer that the front has to come off completely to do checks.

Thanks for any help you might offer.

Russell
Peephole
by: Shawn/admin

Does it have a peephole in the front so you can see the igniter working? Whirlpool has a small peephole in the front with a little cover you snap off. A lot of GE dryers the peephole is actually under the dryer (right front corner), which is supposed to be viewed with a mirror.

See if you can tell if the igniter is coming on then going out when you hear the click. If so I would suspect the valve. If the igniter isn’t coming on replace the igniter.
Yes to that.
by: Anonymous

Hey Shawn,
Thanks for the comments. The peep hole is there and the igniter works. I have done lots of plumbing and am confident with gas leak detection. Is it worth it to replace the valve? Thing is like new. Any chance the valve can just be cleaned...like debris got in it or whatnot? Is there a way to tell if the solenoids are operating the valves? I did check all the overheat protection devices and the flame sensor they are all good. As stated, solenoids are new.

regards,
Russell
RE
by: Shawn/admin

If the igniter comes on then you hear a click and the igniter goes out but the flame doesn’t light then you have a bad set of coils or a bad gas valve. You already replaced the coils so I believe your valve is bad.

I don’t recommend trying to change the valve yourself but if you are confident and if you know how to check for gas leaks then you should be ok.
Gas dryer heating issue
by: Steve

Hi, I recently replaced a Kenmore gas dryer that would spin but not heat with a 5 year old Whirlpool dryer. The Whirlpool is exhibiting the same symptoms as the Kenmore, spin but no heat. I see glow through the sight hole. Any ideas???
Thanks in advance
Sensor 338906
by: DavidMandina@Gmail.Com

I currently have a issue with same model.Not heating.While looking it over I noticed that one side of sensor prong is broken off.I figured problem solved.While getting ready to order new sensor I decided to do a bit of research.Is it just the defective sensor or since igniter does not glow red;but ohms out good should I also consider the thermo fuse??

Thanks in advance;Dave
igniter not working
by: Anonymous

Hi,
My clothes take at least three full cycles to dry and even then are still a bit damp. We called the repair company and the guy said the igniter needs to be repaired. But the part will not be arriving until next week. Is it safe to use the dryer until then?

Thanks in advance
gas flame ignites then goes out
by: BOB

My kenmore dryer ignites the flame and after a short time goes out.. then repeats that
Flame Time
by: shawn

Define "a short time" under normal working conditions the flame should only be on for a minute or so at the time (first cycle may be longer).

If it is not staying on long enough it could be a clogged vent causing it to overheat quickly or you could have a faulty thermostat.
Radiant/Heat Sensor Issue (bad?)
by: Andaval

Hi Shawn, my gas dryer stopped heating one day, the Igniter would not glow. I replaced both coils and got the Igniter to glow but would never get a flame. The original sensor read open. After purchasing two new radiant sensors from different vendors, I am still with the same issue. The two brand new ones read closed but they never open up when installed next to the flame; the Igniter glows for ever. I have been drying my clothes by turning the dryer on and shorting together the two sensor wires, until I see the Igniter glow, and then open them up and viola! always get a flame. My question: what are the odds of two brand new sensors being bad? Might there be something else in the circuit that could cause this failure? I haven't purchased a new sensor because I do not need a collection of them...
Thank you for any comment or help.

by: shawn

I wouldn't think you would have two bad sensors but it is possible. Make sure there isn't something blocking the heat getting to the sensor. Try replacing the ignitor because it may not be getting hot enough to trip the sensor.
Sensor Wiring
by: Frank

Simply wondering which color wire connects to the contact with the red painted dot on the flame sensor. I took it off with out marking and now I don't want to put it back together. Blue or white to the red painted tab?

Thermodisc 338906 on a kenmore 87874100

Thanks

by: shawn

It shouldn't make a difference on how you connect the wires on the sensor it should work fine either way.
Wire color
by: Anonymous

Thanks. That's What I began to figure as I watched a vid and the guy switched them without saying anything and when I did the test I just touched them to watch the igniter glow. Thanks for confirming.
Gas dryer no glow
by: Dave

Checked fuses sensors igniter... Replaced igniter but still getting a 0 Ohm reading no resistance on the igniter. Could the new one be bad too? Have even tried jumping fuses but still no glow, no heat.
burner won't stay lit
by: Greg

I just checked the coils. The 3 terminal coils has these readings:
1 to 2 = 1.351K ohms
1 to 3 = 549 ohms

The 2 terminal coil reads 1.293 K ohms.

The igniter glows red for a while and then the burner lights up. It stays lit for about 4 1/2 minutes, then goes out. It doesn't come back on unless I shut the dryer off and let it cool down completely.

I have completely cleaned the dryer, lint shut, and the vent tube going outside are totally clean.

Does this sound like the coil is bad?

Thanks
Greg
Dave and Greg
by: shawn

Dave,

You should get a reading across the ignitor. Try setting your ohmmeter on a higher setting. If still open replace ignitor.

Greg,

Replace the coils, you can't very well check these coils but most of the time the issue you are having is a bad coil.
May tag no glow.
by: Anonymouseric

I am getting the glow intermittently and ohm the igniter it showed bad. So I ordered a new one installed it ohm good but it isn't glowing. Any recommendations on where to look now.
burner won't stay lit
by: Greg

Thanks. I replaced the coils and all is well. (Quite a while ago.) I had another issue since then, the thermal fuse died. I replaced it and the dryer has been working great ever since. I bought some extra parts, since they don't cost much, to keep on hand in case I need them in the future.
Burner ignition glows times out no flame lit
by: Adam

Have changed the two gas coils still no flame. Should I through in a new flame sensor? The rest of the hi temp thermostat all check out to be ok.

Sounds like you have a bad gas valve. You might need to call a professional you don't want to mess with gas unless you know what you are doing. If you do you must check for gas leaks.

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