Author Topic: Wiring Diagram Question for Roper Electric Dryer  (Read 700 times)

Offline jfw0928

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Wiring Diagram Question for Roper Electric Dryer
« on: February 18, 2014, 09:56:14 PM »
Hello,

I'm struggling to learn how to read these wiring diagrams. I understand electronics: ohms law, kirchoff's law, voltage, current, resistance, series and parallel circuits, resistors, capacitors, etc. But, these wiring diagrams are kicking my butt. Somehow I have to get past it to take my skills to the next level. Appreciate any help offered on this one.

So, I found an Roper Electric dryer (REX4634KQ1) on the side of the road. It was pretty roached but, I figured that it was good for parts at least. It runs but, does not heat. I currently have it disassembled with the door switch bypassed. I get 240V on the terminal block. The push to start switch is good (has continuity). As are the - thermal fuse, operating thermostat, thermal cut off, high limit thermostat, and heating element (9.8 ohms). I get continuity between motor terminals 1 & 2 with power on and timer on. I get continuity between motor terminals 5 & 6 with the centrifugal switch engaged (can also see it move when starting the machine). With all of the preceding my gut tells me that the timer is bad. However, I want to know how to prove it. I was thinking that it could be proven by testing, and not finding, continuity on the timer's switch #2. Alas, I get continuity between red & black terminal of the timer with the timer on and the motor running. Can someone please tell me where my logic is messed up and how to prove this timer is bad? Thank you in advance. The wiring diagram is attached.
« Last Edit: February 18, 2014, 09:59:26 PM by jfw0928 »

Offline tgoods

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #1 on: February 19, 2014, 12:33:22 AM »
It's possible for a switch contact to show continuity with an ohmmeter but open under load.  Check for a voltage drop between R and Bk with the dryer running.  If you find 240vac, the timer is bad.

Offline fairbank56

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #2 on: February 19, 2014, 08:16:19 AM »
  You should not be making continuity checks with the dryer plugged in. Unplug dryer, if dryer does not have a buzzer, transfer the red wire from R to the unused BK terminal on the timer. If there isn't an unused BK terminal, unplug from BK terminal the wire that goes to the timer motor, transfer the red wire from R to that BK terminal. Plug dryer back in and turn it on. If you don't get heat, problem is not the timer.

Eric
« Last Edit: February 19, 2014, 08:17:12 AM by fairbank56 »

Offline jfw0928

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #3 on: February 19, 2014, 11:49:45 AM »
TGoods, thank you for your reply and advice. I checked the voltage across the red and black terminals and found 240 V. I'm assuming that the logic is that if switch #2 of the timer is open then all of the voltage in that leg of the circuit will be dropped across it. Please correct me if this not accurate.

However, Eric (thank you for your reply and advice), I also switched the wires as you prompted and the result was that there is not any heat and the dryer does not run. Which confuses me because I am assuming (correct me if I am wrong) that the logic here is to bypass the timer altogether.
« Last Edit: February 19, 2014, 11:50:37 AM by jfw0928 »

Offline fairbank56

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #4 on: February 19, 2014, 12:35:44 PM »

  If you measured 240vac across the BK and R terminals with dryer running in heat mode, then yes, the timer is bad. Yes, the purpose of moving the red wire directly to the BK terminal was to bypass that timer contact. If there is a short somewhere in the heat circuit, it may have tripped your panel breaker.

Eric

Offline jfw0928

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #5 on: February 19, 2014, 12:47:11 PM »
Eric, after switching the red wire to the unused blk terminal on the timer, I switched it back and the dryer ran again without heat. So, with the red wire switched to the black terminal, the dryer is dead. With the red wire connected to its normal terminal on the timer, the dryer runs without heat.
« Last Edit: February 19, 2014, 12:54:34 PM by jfw0928 »

Offline fairbank56

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #6 on: February 19, 2014, 01:31:34 PM »

  So, with red wire back on the BK terminal, monitor the voltage to ground there. Should be 120vac. Now hit start button, if voltage drops, you've got a bad connection somewhere. Either power cord connection block, dryer receptacle or panel breaker.

Eric

Offline jfw0928

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #7 on: February 19, 2014, 05:21:49 PM »
Bingo!!! It was a matter of a couple of issues.


  So, with red wire back on the BK terminal, monitor the voltage to ground there. Should be 120vac. Now hit start button, if voltage drops, you've got a bad connection somewhere. Either power cord connection block, dryer receptacle or panel breaker.

Eric

I was able to run another dryer connected to the same receptacle without any issues. So, that left the power terminal block. The only thing I can think of is that, by me checking and handling the wire harness just behind the terminal block, contact was provided to a just previous loose connection. Because now, when I place the red wire on the available black terminal of the timer, I get heat. When I replace the red wire to the red terminal of the timer, dryer runs but, no heat. So, along with the 240 V reading between the black and red terminals of the timer, the presence of heat when switch #2 of the timer is bypassed, proves that the timer is bad. However, when purposely wiggling that same area of the harness, I am not again able to reproduce the bad connection - the heater always comes on now with the timer switch #2 bypassed. Go figure. Thanks to both of you guys for your help. I learned quite a bit here and really do appreciate it.

I'm going to push my luck just a little further and ask the following - In the wiring diagram, between motor terminals 1M and 2M, is a switch. What is that switch for? And, what activates it? I'm pretty sure that the centrifugal switch is between 5M and 6M. Thanks again.

Offline fairbank56

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #8 on: February 19, 2014, 08:22:15 PM »
  Both switches are activated by the motor centrifugal mechanism. The switch between 1 and 2 completes the heater circuit. This is a safety feature so that if the motor stops, the heat is turned off. The switch also completes the timer motor circuit.

Eric
« Last Edit: February 19, 2014, 08:24:47 PM by fairbank56 »

Offline jfw0928

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Re: Wiring Diagram Question for Roper Electric Dryer
« Reply #9 on: February 19, 2014, 11:38:05 PM »
Thank you Eric.

 

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