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Budget Appliance Repair

Generic question about diagnosing a not heating complaint on gas dryer

7 posts in this topic

Just a generic question for all other techs here:

 

You have a gas dryer with a "Not heating" complaint.

 

You show up and start dryer check temps and it is heating fine, running for 5 to 10 minutes checking cycling temps in hi and low settings all are OK.

 

What do you do:

 1) keep waiting and watching to see if ignitor glows and burner doesn't light to know and prove you have bad gas valve coils.

     A) How long do you wait to prove this?

or

 

 2) Just assume you have bad gas valve coils without proving it and go about cleaning/checking rest of unit and replacing coils.

 

The reason I ask is I had another one today that took 16 minutes before the coils actually broke down and failed so that I had proof this was the problem, (I really detest replacing something if I don't have definite proof it is bad).

 

In the past I had one that I had let cycle on/off for about 1/2 hour and it never missed a beat so I assumed it was OK and just had bad users/tenants.  Got a call back next day said still not working, went out and checked again - this time coils broke down and failed in 5 to 10 minutes.

 

So basically how long do you let it cycle before giving up and saying all is OK or do you just normally assume must be a gas valve coil problem and replace them?

 

Thanks for any feedback on this..................

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if they have warranty coverage i will replace them after watching 3 on off cycles regardless of failure.  If paying cash i will watch for 15 min or so and then talk to the cust and tell them it is most likely coils but they are working right now.  with the low price of the part most just say replace them

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It takes a little time. Don't know if I can help you with that but I've had pretty good luck with this technique:

I'll wet my towel and wring it out a little; put it in the dryer to simulate a wet load.I unplug the dryer and hook up my meter set on AC volts across the cycling thermostat. I use the insulated alligator clip leads. My one meter beeps when it gets voltage so I don't have to watch it. Then I start the dryer and wait for the flame to go out. When it does, 120 volts should appear across the operating t-stat indicating that it is open. This is normal. If there is no voltage across the cycling t-stat when the flame goes out, then something else in the circuit opened. I don't think it's possible for a thermal fuse or heat sensor to fail in this way, so I'm down to either the hi-limit or the coils. With the dryer still running, the flame out, and no voltage across the cycling t-stat, I use my other meter to check for voltage across the hi limit... voltage = open switch. So there's an airflow problem/ weak hi limit. If the hi limit is still closed, I replace the coils. This can be done easily and safely on some dryers; the Whirlpool 2-roller is one. With others(4-roller) it can be a little dicey. with others you may have to unplug the dryer and use a continuity check.

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I usually call the customer 10-15 minutes before I get there and have them turn the dryer on that way it is quicker to see it fail. Also make sure you check the air flow.

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if they have warranty coverage i will replace them after watching 3 on off cycles regardless of failure.  If paying cash i will watch for 15 min or so and then talk to the cust and tell them it is most likely coils but they are working right now.  with the low price of the part most just say replace them

 

This sounds like the best idea to me, (I don't do warranty work so I don't have that part of the option).

 

I hate waiting over 10 minutes doing nothing just waiting for the coils to fail, (it only take the first 3-5 minutes to check that the airflow/cycling temp is correct in hi and low heat mode while waiting - that is the first thing to do while waiting for the coils to fail).

 

In my experience, most of the time failing coils will show up within 3 to 4 cycles, (under 5 minutes), unless they are just on the verge of failing.  It's those few times that they seem to take forever to fail that I was looking for some kind of shortcut for proof.

 

Thanks guys.

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with an empty load, the Coils would (should) cycle more often

and may catch the fail sooner,

OR may need to be energized for an extended time for them to heat / fail.

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An educated guess of the coils usually flies. I've had better luck putting in a load and keeping the coils energized for a while to see the smoking gun.

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