Dry will not dry clothes / heats for a few cycles then stops

[revto9]

I have a MDG9700AWW dryer.  I have taken this thing apart and check the thermostats with a volt meter,  the thermistor the ignitor.  They all checked out good.  Put it together and ran it empty and the dryer was cycling up to about 120 degrees then down to 100 and back up.  Everything looked good.
Put some semi dry clothes in and it seem to do the same thing.  Put some wet clothes in the thing and it cycled a few times and then just stopped heating up.  It kept running but no heat.  I have checked the duct work as well.   Any ideas what to look at next?   I am ready to throw the thing in the trash after only a couple of years.

[jumptrout51]

 Did you check this temp with the exhaust duct removed from the back?
If so,
120 degrees should be your minimum temp. Replace your high limit thermostat. I believe it is opening too soon.

[RegUS_PatOff]

With an empty load, Timed Dry, hi-heat, the vent temperature should cycle somewhere between 135F and 160F.

It could also be an intermittent Gas Valve Coil (very common problem) $20 / set

When the Flame goes out, does the Glow Ignitor start back up (and the Flame doesn't) ?

[revto9]

I was using the temp off the panel in service mode to monitior the temperature.  Not sure how accurate that is but it seems to be close.
I don't know if the ignitor glows or not.  I put the panel back on to run the dryer.   I will check tonight,  I will remove the front panel and run it. 
Is there a way to check the coil to see if that is the problem.   I will also make sure I have the dryer on timed dry at high heat and recheck the temp.
It does not get anywhere near 150 degrees.  The local parts place seems to sell alot of the coils and thermal fuses.   But they also sold me this wonderful machine and said I would have no problems for a long time.   I guess a long time is relative.

[jumptrout51]

Using a thermometer at the exhaust vent with the vent removed and no garments in the dryer...check your temp. Leave it there for about 15 minutes so that the heat can stabilize.

[RegUS_PatOff]

...Is there a way to check the coil to see if that is the problem... 

No, just by visual of the Ignitor/Flame sequence ...

[JWWebster]

You can feel it after it has been working and quits. If it feel hot as heck and won't come on then guess what? It is bad. Replace em both. They come in pairs and are the same age.

[revto9]

Well, I left the front panel off and cycled the dryer.  The ignitor is functioning and the gas comes on shortly after.  With the panel off it does not stay on very long.  To much outside air I guess.  Tested the coils with a volt meter and they check out according to the manual.  Put the front back on and it heated to around 142 degrees.  Worked fine empty for about 15 minutes.  Added semi wet clothes and it was cycling correctly for about 10 mintues and then nothing but tumbling.  No heat cycle at all.  It appears to be a problem after things heat up.  Could this still be the coil or maybe the thermosat?
I don't believe this has a thermo fuse.  I couldn't find one anyways.

[RegUS_PatOff]

It could also be an intermittent Gas Valve Coil (very common problem) $20 / set

When the Flame goes out, does the Glow Ignitor start back up (and the Flame doesn't)  ?

[revto9]

When the flame goes out it drops about 10 or so degrees and then the ignitor glows and it flames back up.  The flame is a nice blue flame which you would expect when it has plenty of gas.   I don't think it even gets to that point once it heats up and stops working.  It just stops calling for more heat and sits there and tumbles.

[JWWebster]

Normal operation that flame stays on 30 seconds and shuts down then it kicks back on with demand. The gas does NOT stay on continously or the clothes would burn up. Everthing is working fine except those coils are getting hot and quiting. Wait a long time and it will work of for 15 more minutes. Your problem is a very common failure on these dryers. Replace those coils.

[JWWebster]

Here is an excellent page I borrowed from my Samurai bud:
http://sites.google.com/site/sublimeappliancerepair/washer-will-not-spin/agitator-woes/dryer-will-not-work/how-do-i-get-inside-my-dryer/gas-dryer-quits-heating/more-gas-dryer-enlightenment

[revto9]

Well,  I put the coils on this morning.  It has made it through one load of clothes.  It appears that was the problem.  Thanks everybody for your help I really appreciate it.