Dryer not getting as hot as it used too

Dryer Repair
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1

The basic problem is that the dryer is not getting as hot as it used to (even on the highest setting). The clothes used to come out very hot to the touch but now it take a long time to dry. The dryer works fine other than that.

First off, it is not a link blockage problem. I completely dismantled the dryer and cleaned everything. The exhaust run to the outside is about 2 feet and that is clear, also, internal ducting and piping inside the dryer is clear and the lint screen is also clean and clear.

Here is what I am observing of the operation of the dryer as far as the temperature cycling. I am measuring the exhaust temperature with a thermometer (ran with an empty dryer). On the HIGH temperature setting the exhaust temperature climbs up to 160-170F and then the burner turned off. So Far so good. As the exhaust temperature cools I hear a click at about 140F but nothing happens. Then at about 110F another click and then the ignitor warms up and the burner lights. So the temperature over the cycle goes between 160F and 110F. According to the tech sheet that came with the dryer, the ignitor should come back on when the temperature drops 10-15F below the heat turn off temperature (in this case 160F). It is this wide temperature swing between the burning on and off that I believe is causing the low temperature.

I also measured the temperature cycle on all the other settings with similar findings:
Med High Temp : Burner off 150F, Click at 130F but nothing else, Click at 110F Ignitor lights and burner starts
Med Temp : Burner off 140F, Click at 130F but nothing else, Click at 110F Ignitor lights and burner starts
Low Temp : Burner off 120F, Click at 90-100F Ignitor lights and burner starts

So here is what I have done and what I have replaced so far but nothing has fixed this issue.
Replaced the thermistor (part 8577274)
Replaced the Coils (Part #694540/694539)
Replaced the controller board (part W10116565)
Tested the High Limit (205F) Thermostat and it is fine. Thermostat has a closed circuit (no resistance) until ~ 205F and above this it is an open circuit (very high resistance). Also ran a test where I bypassed the High Limit Thermostat and operated the dryer but still had same problem.
Swapped the Heater relay with the Motor relay (no difference in dryer operation)
Put the dryer into Diagnostic test mode and got a beep upon all the input changes.
Tested Thermal fuse and it is fine.

I haven’t tested the resistance of the Ignitor since it seems to be operating properly, but could it be that there is some type of thermal recovery of the Ignitor (or the ignitor is close to failure) that it cannot re-turn on until it has cooled sufficiently and that is why the temperature cycles down to 110F before re-ignition in the test I preformed with and empty dryer?

Any other tests or suggestion of what may be causing this problem of low average dyer temperature? Thanks for any help or feedback.

3

Probably the flame sensor. This is on the burner right next to the ignitor. When the ignitor gets hot, the flame sensor opens allowing the secondary gas valve to open and the gas ignites. The ignitor cannot operate until the flame sensor closes again. Seems like it is taking too long for it to close.

http://www.appliancepartspros.com/whirlpool-flame-sensor-338906-ap2910747.html

Eric

4

Eric,

Thanks for the info. Will try replacing the flame sensor and see if it fixes the issue. Will Post back the results when done. Thanks again.

5

Ok, Replaced the flame sensor but still have the same problem. The dryer heats to 160F and then the flame turns off. The dryer starts to cool and at around a 140F I hear a click but nothing happens. Then at about 110F I hear a louder click and the ignitor comes on and the flame then lights.

Any more ideas of what could be causing this issue??

6

I assume the loud click you hear at 110° is the heat relay. If so, and ignitor comes on right after that and soon after that, burner lights, it appears the ignitor is working fine. The other click you hear at 140° is likely the flame sensor closing. Seems like the thermistor is not sensing properly. You replaced that, so only other thing is an airflow issue. Did you take the blower wheel off and check inside the blower housing under where the thermistor is mounted?

Eric

7

Eric,

I removed the housing around the blower and the housing is completely clean and I can see the thermistor. So that doesn’t seem to be and issue. I also measured the resistance of the ignitor and it is 66 ohms so that seems ok.

The only other thing I have also checked was the temperature selector switch. From the different temperature cycling study above that seems to be working properly. However the tech sheet says that for the Med High setting the contacts on the switch should have contacts 3-5 open, contacts 2-4 should be closed and contacts 1-4 should be closed. When I measure it I get contact 3-5 open (as it should be), contacts 2-4 open (not as it should be) and contacts 1-4 closed (as it should be). However when I measure contact 2-5 that is closed. My guess is that the manual is wrong and they should have said contact 2-5 instead of contact 2-4. The reason I believe this is on the medium temp setting they also state that contact 2-4 should be closed and I measure 2-4 open but 2-5 closed.

I really don’t think this switch is the issue as for the High temp setting the switch has the correct settings and the temperature rises to the correct level. The temperature just doesn’t seem to cycle on fast enough.

Do you have any other ideas of what I should try. Thanks for the help so far.

8

Iv’e run out of ideas. Maybe someone else here can offer something.

Eric