[MikeInMA]

My Kenmore 110.87980100 dryer (Serial # MA3305936) has gone from taking a very long time to dry, to not completely drying a load of towels at all. I'm a generally handy homeowner, having fixed mechanically related problems with the dryer (belt/pulley) and washer before, but I am stumped how to proceed from here. I have tried to diagnosis the problem myself, using a repair book and internet sources, but I need help.

First, I observed the burner operation, with the dryer empty, and found that the ignitor glowed, the gas valves opened, a flame burned (mostly blue); it only burned for 44 seconds before it shut off, remained off for about 1.5-2 minutes, then burned again for only 22 seconds. This is not normal, this is short, right??

Based upon this, I followed the diagnostics reccomended in the book for FLAME STARTS (GAS VALVE OPENS) BUT KICKS OFF QUICKLY (SHORT-CYCLES, LOW HEAT):

1) Airflow: was of course the first stop. I feel I tackled this a couple days before, when I cleaned the lint trap, lint chute, exhaust duct, and exhaust vent thoroughly, as I have a number of times before, with hands and vacuum. This time, I even bought a brush kit, and used those in the lint chute and exhaust duct. A lot of lint came out. The exhaust situation is not ideal, but has worked well enough for 20 years. Flexible metal duct, must go up vertically about 8-9 feet, past the basement concrete foundation, with two 90 degree bends, one where it meets the dryer, the other at the top where it meets the louvered exterior vent.

2) Check for defective flame sensor: checked for continuity (using digital multimeter), was good (0).

3) Check thermostats:

a) 150 degree thermostat on blower housing (lint chute) - continuity was good

b) 250 degree thermostat on heater box - continuity was good

c) Thermostat Heater (surrounding the 150 degree thermostat on blower housing) - continuity with multimeter set on audible was 1.54, with multimeter set on 200 and 2K was 1. ??Is this correct??

d) Thermal Fuse - continuity was good, of course

Can a thermostat be bad even if it passes the continuity test when it is cold??

I did not check the coils, as this was not in the recommended diagnostics for this problem in the book, and I know they are allowing gas through. Should I check them??


The other thing I did, and I realize that it may indicate bad airflow, but again, this unit has run well enough for 20 years with this venting setup, is I ran the empty machine after detaching the external vent; the burner burned for over 5 minutes on its first cycle... I stopped the dryer without letting the burner cycle off at that point.

How long is the "proper" amount of time for the burner to run?

Please answer my questions, and recommend a course of action... I'd truly appreciate some quality help.

Thanks, Mike

[richappy]

You are still getting poor/ turbulent air flow. An air flow meter would confirm this. The fact that it worked "normally" with the ducting off confirms this.
One solution is to buy a 4 inch brush with 15 foot extensions called "Lint eater" around $39 plus shipping.
Another solution is to use a shop vac (higher hp the better) and blow the lint out. Lots of times the lint will bunch up and cause turbulence, the shop vac might just clear it out.

[kayakcrzy]

I have seen people use a leaf blower from the inside of the house, and blow it. Of the hook option, but it works. Tom ********************************************

[MikeInMA]

I appreciate both your responses.

as stated in (1), I did buy and use a brush kit, in fact, it was the LintEater kit.

I know that it could be an airflow problem, but again, it has run well enough for 20 years with this venting setup. So if airflow is a factor, it seems like something else must have happened to cause my current problem.

there are 4 other questions within my first detailed posting, that are very important things that I cannot answer... can anybody answer those??

I'd appreciate any help with that.

[richappy]

Some of your questions can't be answered. Your burner will run as a function of airflow, poor airflow will open the thermostats sooner than "normal".
I missed the fact that you have flexible ducting in the house. This stuff is not per code and will clog easily. You might try using the lint eater with a power drill to get all the lint out. Any partial restriction will cause turbulence. Hold a sock up to the dryer vent, then compare it's rise outside when the ducting is connected, will demo the extent of your venting problem.

[MikeInMA]

Originally Posted by richappy

... Some of your questions can't be answered. Your burner will run as a function of airflow, poor airflow will open the thermostats sooner than "normal".

... have flexible ducting in the house. This stuff is not per code and will clog easily.

... Hold a sock up to the dryer vent, then compare it's rise outside when the ducting is connected, will demo the extent of your venting problem.

1) Can this question, from my initial write-up, be answered:
Thermostat Heater (surrounding the 150 degree thermostat on blower housing) - continuity with multimeter set on audible was 1.54, with multimeter set on 200 and 2K was 1. ??Is this correct??



2) the ducting is the semi-rigid metal kind, except at the 2 elbows, which are rigid. Is that per code? will that clog easily?

I am probably going to change it to as much rigid ducting as I can right now.

3) the sock is a good simple tool, better than my hand, thank you.