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rat454

sub zero 501f freezing up

23 posts in this topic

My sub O 501f ser# M1073712 is collecting alot of ice in the drain trough. It overflows into my ice maker and ultimately killed it.  Before I go and replace a bunch of parts I wanted to understand how and what to check to get to the root cause.  Can anyone help with a service manual that would instruct me how to diagnose each component so I can determine if it needs replacing.

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Need appliance parts? Call 877-803-7957 now!

Does the evaporator cover come off easily.  I can't readily see how it comes off.  To replace the defrost heaters this has to come off correct?

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Thanks for the diagram.  Can you give any tips on how to verify the defrost timer is working properly.   

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one test, manualy turn it slowly while measuring the voltage at the Defrost Heater ..

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WOAH WOAH WAIT!!! If you look at the drain trough, does it look like a frozen waterfall? If so, it is NOT your defrost drain heater. You need to install a 4-20-148-0 Heater package. it comes with two heaters... USE BOTH! some techs will only install the auxilliary heater and not replace the drain trough heater... REPLACE IT! even if the original ohms out good. I will peel the old one off and use a heat gun to warm up the drain trough. then stick the new one on.

Also, take a turkey baster and flush that drain out as well when all is defrosted, make sure that is clear as well.

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The whole drain trough is solid ice all the across and I'd say it kinda looks like a waterfall.  So its the trough heater that's my problem?  There is a stainless wire that goes into the drain tube.  Could that be bad too?  Is this part of the heater kit, i don't see it in the picture?

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[user=72560]rat454[/user] wrote:

The whole drain trough is solid ice all the across and I'd say it kinda looks like a waterfall.  So its the trough heater that's my problem?  There is a stainless wire that goes into the drain tube.  Could that be bad too?  Is this part of the heater kit, i don't see it in the picture?

It is not part of the kit, However it is one of those situations where, the cost of the part is minimal vs, the time to de-ice and get to it. If it were MY refrigerator, I would replace it just for peace of mind. And I would ohm it out as well, if the old one is good, I would now have a backup spare should the other one go out. I keep them on the truck so when I have it apart, I can ohm it out and if the customer needs it, I have it.

But in your situation where you want to do this once and forget about it, change it.

Allow yourself a good two hours to do this. TAKE YOUR TIME!!! do not scrape or break out the ice, use a hair dryer or heat gun (If you just opt to turn the freezer off to de ice it, make sure that drain pan does not overflow and water all over your floor.)

remove the icemaker, then the 4 screws holding up that crisper glass shelf. After you remove the ice from the drain trough, is there frost on the back wall? If so, you are going to have to remove the back panel. to do this, DISCONNECT ELECTRICAL POWER TO THE FREEZER EITHER BY UNPLUGGING IT OR TURNING OFF THE CIRCUIT BREAKER! (That was from my old technical manual writing days) remove the light shield on top, you will see a grille for your evaporator fan blade, there are two stainless screws you remove. Now remove the grille and the back panel should come forward. disconnect the pwer and ground wires from your cold control and you will now be able to free that panel from the unit. Once again, use a hair dryer to de ice it.

Take your time in assembling the new heater in place... CAREFULLY tuck the wires behind the channel (you will see what I mean as you progress) make sure none of them are pinched when you tighten it all back together.

Sounds scary but it isn't, just read the directions that come with the heater very carefully and you can do it.

 

Good luck!!!

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Thanks for the feedback.  Can you give me the part# of the drain tube heater?

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Searches gave me 3013550 but looks like not available.

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[user=72560]rat454[/user] wrote:

Searches gave me 3013550 but looks like not available.

it is but Sub Zero went through a part department debacle. There is a new part number but I do not know what that part is. I would check RepairClinic.com or call Sub Zero at 1-800-222-7820 and ask for the parts dept and they can get you the right part #

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should the defrost terminator be clipped to the center top of the evap?  I took the evap cover off and it was just hanging not clipped to anything.  It looked right by the length of the wires that it should be clipped there.   i unhooked and checked the resistance and it read open.  should it be open when at room temp?  Also part of the defrost heater coil was not pressed into the evap coil.  is this normal?  this would probably be causing poor transfer of heat to deice the coils right?

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what is the defrost terminator's purpose.  when i look at diagrams online for a 501f  it is not in the same place as mine.  its on the left top facing the freezer.  I found an ice maker for $55 at filter outlet.com  part # RIM900.  says its a replacement for 4200520.  What do you think.  much better price than 130 everywhere else ive seen.

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Defrost Terminator should be clipped onto the Evaporator ..

Defrost Terminator should be open at room tempearture.. that's it's purpose,

to stop the Defrost when it gets warm.

 

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I turned the defrost timer to make the defrost cycle start.  The drain tube wire were hot and the wires got hot but the evap heater was not hot.  The evap heater showed no voltage.  I bypassed the terminator and got hot.  Is my terminator bad?  I could check it by putting a heat source (hair dryer)  to right?

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Should'nt the terminator be closed until it gets warm after the defrost cycle nears its end then open and stop current and heat flow?

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The terminator latches the current flow to the evap heater correct.  When the evap is cold the terminator is closed and allows current flow.  The defrost timer turns the compressor off when in defrost cycle and the evap eventually raises in temp from the evap heater and in turn heats the terminator causing it to reach temp then go open.  By then the defrost timer times out and the cooling cycle turns back on and the terminator waits for another defrost cycle correct?  i believe my terminator is bad.  i checked ohms with a hair dryer on it and it kept reading open.

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I've basically figured out the terminator is bad causing the evap to produce ice uncontrolled.  My defrost timer, drain tube heater and trough heater are all ok.  They all heated up on the defrost cycle.  The evap heater wouldn't heat up cause the terminator was not working.  I tested the terminator by setting it in a bed of ice and it continued to be open meaning no current flow.  I however will replace the terminator and the trough heater cause its coming apart and has no more good sticky stuff on it to keep it stuck to the trough.  I won't be able to test the evap heater until i get the terminator.  Oh also i will replace my ice maker.   Will post results.

Thanks for the help DrFrige and RegUS. 

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[user=72560]rat454[/user] wrote:

...  I tested the terminator by setting it in a bed of ice and it continued to be open meaning no current flow.... 

yes, then it's bad...

only alows current flow when it, and the Evaporator, are cold

once the Evaporator frost melts, the Defrost Terminator is no longer cold and it then opens ...

You could test the Defrost Heater, by bypassing (jumpering) the Defrost Terminator for a few minutes ...

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Does the heater kit include a defrost terminator.  Looks like one in the picture.  Called supplier and they didn't have any details on the components.

 

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