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Samurai Appliance Repair Man's Blog

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Gas dryer not heating, troubleshooting with only a jumper wire


Samurai Appliance Repair Man

1,932 views

Problem: I'm on a gas dryer service call-- no heat complaint.

Solution: Using only my jumper wire at the main board, I proved a problem with the Neutral sense line from the motor and made the burner fire up. 

Question: At what two points did I place my jumper wire to troubleshoot this problem? 

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26 Comments


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  • Team Samurai
Samurai Appliance Repair Man

Posted

Bonus question: Which two teats on the cow's udder did I jump to make the burner fire? 

 

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  • Like 1
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LearningTech

Posted

Bonus= 2 closest to the head, so that you were as far back as possible.

  • Like 1
  • Haha 1
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Connection 3  You jumped pins 1 and 2

 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

1 hour ago, Rich Armstrong said:

3(2) > 7(1)

Better have a really big jumper cuz once that heater relay closes, you’ll have a dead short. Arcy-sparky! 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

10 hours ago, Quick said:

Connection 3  You jumped pins 1 and 2

 

All that does is bypass the heater relay. That will fire the heater but may not be the source of the problem. What controls that relay? Could the motor Neutral sense affect that?  

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Quick

Posted (edited)

3 hours ago, Samurai Appliance Repair Man said:

Could the motor Neutral sense affect that?

I would think so. The motor was running. Jumping the relay bypassing the sensing wire is testament sensing wire or something to do within the board itself is bad.

So what did you do maybe jump connection 7 pin 1 to connection 6 pin one? proving it's a bad wire rather than board?

Edited by Quick
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  • Team Samurai
Samurai Appliance Repair Man

Posted

11 minutes ago, Quick said:

So what did you do maybe jump connection 7 pin 1 to connection 6 pin one?

Not unless I wanted to make a dead short by opening the door and getting the board to close that lamp relay. Arcy-sparky!

F05361AB-BA59-48AA-9731-824ED2C3C628.gif

 

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Just now, Samurai Appliance Repair Man said:

dead short by opening to door

Said nothing about opening the door L.O.L.

 

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Rich Armstrong

Posted

Could you make a Webinar on the Neutral Sensing Line Samura? You posted a pop quiz a cpl weeks ago that featuring the Neutral Sensing Line. I took all the advanced courses and this was never discussed. Of course you’d never guess I took all the advanced courses after jumping 3(2) 120 vac  to 7(1) Neutral lol 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

1 hour ago, Quick said:

Said nothing about opening the door L.O.L.

 

Does it ever make troubleshooting sense to create a short or a potential short? It’s like chess- gotta be thinking several moves ahead. Better to anticipate problems than react to them. 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

22 minutes ago, Rich Armstrong said:

Could you make a Webinar on the Neutral Sensing Line Samura? You posted a pop quiz a cpl weeks ago that featuring the Neutral Sensing Line. I took all the advanced courses and this was never discussed. Of course you’d never guess I took all the advanced courses after jumping 3(2) 120 vac  to 7(1) Neutral lol 

That’s why you gotta watch my webinars! The training is just the beginning and gives you the ability to understand them and follow what I’m doing without getting lost in the elementary circuit stuff. I have several webinars where I show sensing lines in different applications. They’re used all over the place in all computer-controlled appliances. General rule: when you see multiple lines doing the same thing going back to a control board (Neutral, Line, doesn’t matter) and one is unswitched while the others are switched, most of the times those switched lines are sensing lines telling the board about something going on in the machine.

Another example in this schematic: 7-2 is a sensing line for the door switch. The board uses this to know when the door is open and thus to close the relay at 6-1 and turn on the drum light. 

  • Like 1
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7 minutes ago, Samurai Appliance Repair Man said:

Does is ever make troubleshooting sense to create a short or a potential short? It’s like chess- gotta be thinking several moves ahead. Better to anticipate problems than react to them. 

Yes sir. I saw it. I would not have opened the door I can assure you.

This is a good one. I'll let someone else give it a shot from here.

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  • Team Samurai
Samurai Appliance Repair Man

Posted

6 minutes ago, Quick said:

I would not have opened the door I can assure you.

Good. I hope you also see that jumping 7-1 to 6-1 is not a useful troubleshooting move even with the door kept closed. Does nothing to reveal the problem and could only create another problem.

But you have an opportunity to redeem yourself on the bonus question! 

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11 minutes ago, Samurai Appliance Repair Man said:

But you have an opportunity to redeem yourself on the bonus question! 

Damn your puzzels are difficult. Teats 5 and 6 while holding the tail up?

  • Haha 1
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benstickell

Posted

Connector 7 Pin 3 to Neutral lug on the terminal. Thanks for all the knowledge and building an awesome community! What gauge wire should be used? Would 14g be adequate?

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MarcusF

Posted (edited)

7-1 to 7-3 is what makes sense to me. We've got a good Neutral at 7-1 (assuming that Neutral at the outlet is good), and 7-3 is used as the Neutral path for the steam valve as well as letting the board see if the centrifugal switch in the motor is closed. If Neutral isn't present at 7-3 because the centrifugal switch isn't closing, we can fool the board by providing that Neutral from 7-1 instead. 

Edited by MarcusF
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  • Team Samurai
Samurai Appliance Repair Man

Posted

This whole quiz hinged on two things: 1) recognizing sensing lines and 2) knowing how computers use sensing lines to make decisions about which loads to supply with power or to cut off power supply. I gave a big clue in the quiz by referencing the Neutral sense line for the motor. Several of you picked up on that and figured out the correct answer (jump 7-1 to 7-3). Good job!

You were able to figure this out because: 

  1. You knew which line to look for when I mentioned Neutral sensing line for the motor (@7-3); and 
  2. You understood the function of that line. Function is something I stress a lot in my webinars. If you understand the function of something (what it’s supposed to do) you won’t get headfaked by whatever cute name the manufacturer calls something (or, in this case, don’t call it anything; they show it to you on the schematic and you understand its function because that’s the mojo you bring as a tech who understands how circuits work).

Knowing the above two, you cleverly deduced that you could “hack” the Neutral sense circuit by simply jumping over to 7-1, your unswitched Neutral and see if the burner fired up. If it did, you know the problem is in the motor’s centrifugal switch (new motor).

All your troubleshooting was done from the board. You save the tear down for when you return with the new motor and fix the problem. Two trips, one tear down and a guaranteed fix. BOOYAH! 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

51 minutes ago, benstickell said:

What gauge wire should be used? Would 14g be adequate?

This is just a sensing circuit meaning it’s not powering a load. So no significant amps to worry about. In this special case, you could use any size jumper and it would be fine. In general when using jumpers, you need some idea of the amperage you’ll be jumping. If there’s an AC load like a motor or a heating element, wire gauge  matters. 

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mefixit

Posted

so by jumping 7_1 to 7_3 is that tricking the neutral to think the sensing line is ok?

 

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  • Team Samurai
Samurai Appliance Repair Man

Posted

4 minutes ago, mefixit said:

so by jumping 7_1 to 7_3 is that tricking the neutral to think the sensing line is ok?

 

Yep. That's the "hack" I referred to in my previous reply. The non-analytical troubleshooting techniques of jumping and cheating are basically strategically-chosen and skillfully-applied hacks to prove or disprove a troubleshooting hypothesis. Got a whole webinar on jumping and cheating that you may want to watch. 

  • Like 1
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Budget Appliance Repair

Posted

17 hours ago, Samurai Appliance Repair Man said:

This is just a sensing circuit meaning it’s not powering a load. So no significant amps to worry about. In this special case, you could use any size jumper and it would be fine. In general when using jumpers, you need some idea of the amperage you’ll be jumping. If there’s an AC load like a motor or a heating element, wire gauge  matters. 

Samurai, have you every disassembled one of these failed motor switches to see what is failing - I kind of assume it's something mechanical since that sensing circuit isn't a high amperage load that you would think would destroy the points?

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mefixit

Posted

17 hours ago, Samurai Appliance Repair Man said:

Yep. That's the "hack" I referred to in my previous reply. The non-analytical troubleshooting techniques of jumping and cheating are basically strategically-chosen and skillfully-applied hacks to prove or disprove a troubleshooting hypothesis. Got a whole webinar on jumping and cheating that you may want to watch. 

will watch that. thanks.

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