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 > Changing refrigerator cooling unit...New or Refurbished??

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SJ-Chris

San Jose, Ca

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Posted: 11/14/20 07:23pm Link  |  Quote  |  Print  |  Notify Moderator

One thing I didn't check (...and probably should have!)...but I'm learning as I go here...

I didn't check the thermistor. My understanding is that if those go bad, it will make it (usually) so that it doesn't stop cooling.

Does a failed thermistor ever result in ZERO HEAT in the refrigerator?? I'm guessing no but would like to hear what you think...

Thanks!
Chris

PS: I absolutely LOVE this forum and appreciate the RV community and the help they provide always!


San Jose, CA
Own two 2015 Thor Majestic 28a Class C RVs

Old-Biscuit

Verde Valley

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Posted: 11/14/20 07:33pm Link  |  Quote  |  Print  |  Notify Moderator

SJ-Chris wrote:

One thing I didn't check (...and probably should have!)...but I'm learning as I go here...

I didn't check the thermistor. My understanding is that if those go bad, it will make it (usually) so that it doesn't stop cooling.

Does a failed thermistor ever result in ZERO HEAT in the refrigerator?? I'm guessing no but would like to hear what you think...

Thanks!
Chris

PS: I absolutely LOVE this forum and appreciate the RV community and the help they provide always!


If thermistor fails fridge SHOULD go into 'Limp' Mode which allows for continuous cooling
That is why unplugging thermistor leads at circuit board will make fridge to operate continuously and cause VERY low temps in freezer AND Food compartment IF--IF cooling unit is capable of cooling

If fridge dose cool down...replace thermistor
If it doesn't...force cool by direct energizing element lead

But this is ALL mute....cause you have already removed cooling unit so NO testing can be done

Buy NEW cooling unit and new element


Is it time for your medication or mine?


2007 DODGE 3500 QC SRW 5.9L CTD In-Bed 'quiet gen'
2007 HitchHiker II 32.5 UKTG 2000W Xantex Inverter
On the Road Debt Free April '07
Off the road still Debt Free Jan. '14

SJ-Chris

San Jose, Ca

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Posted: 11/14/20 08:55pm Link  |  Quote  |  Print  |  Notify Moderator

UPDATE!

Well, I *thought* I had everything figured out and was about to order the new cooling unit ($650) and a new heating element ($35). But I decided to test my thermistor. Yes, I know NOW that that should be among the first things to check...but I didn't know that until now. (And now I have my fridge out and the original cooling unit removed).

I put an ohm meter on the thermistor to check the resistance. It is coming back as an open (infinite resistance...as in the ends aren't connected). I am very confident in my measurement. If I touch the ends of my ohmmeter together it shows me Zero ohms. If I check a simple piece of wire, it shows me some ohms. But when I probe the two contact points on the thermistor it comes back as infinite (not connected). Do thermistors fail like that? (Note: Yes, I am very confident that my probes are making contact with metal inside the thermistor connector.)

Question: Would that have any chance of causing ZERO cooling inside my fridge and freezer??? I have (before removing the fridge and cooling unit) tried on propane for hours and also plugged in to 110v for hours and got ZERO cooling.

Suddenly, I'm not sure whether or not my cooling unit is bad. How else can I test this system to figure out what is bad?

From my discussion with the online "cooling unit" tech, it sounds like the 3 main components that can go bad are:
1) The heating element (although mine got hot so I don't think it is the problem.
2) The cooling unit.
3) The control panel/board.

I guess "bad thermistor" could be on that list too.

Do I need to put it all back together, unplug the thermistor, and re-test the refrigerator to see if it works? If it really is infinite resistance on the thermistor, then isn't that the same thing as having it unplugged??

Could it be the control board? How often do those go out? (is it rare or common?)

Thanks!!
-Chris

Boon Docker

Mountain Foothills of Southern Alberta

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Posted: 11/14/20 11:21pm Link  |  Quote  |  Print  |  Notify Moderator

When a thermistor goes bad it causes the fridge to become extremely cold. If the "heating element" was getting hot and the fridge not cooling then the cooling unit is shot. Time to replace it.

SJ-Chris

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Posted: 11/15/20 02:42am Link  |  Quote  |  Print  |  Notify Moderator

General question about refrigerator operation....

(I'm trying to determine if in fact my cooling unit is dead)

Question: If the heating element is fine and it is heating the unit/stack AND if the cooling unit is good, then is there any way that the refrigerator would NOT be getting cool??

I know that the heating element was working prior to me pulling the refrigerator but I was getting no cooling in the fridge whatsoever.

Let me know.
Thanks!
Chris

wa8yxm

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Posted: 11/15/20 04:16am Link  |  Quote  |  Print  |  Notify Moderator

SJ-Chris wrote:

Summary: When replacing the cooling unit on your refrigerator, would you go with a refurbished unit ($450) or a new unit ($650)??


Normally I have no issue with Refurb stuff. for I know it's been tested and works.. BUT in this specific case NEW.. always NEW Never Refurb.

The original failed because (most likely) The metal of which it is made got old and tired.. and the REFURB likely did as well. The odds of failure in another spot bother me.


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after a semi "nicked" it. Still have the radios
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dougrainer

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Posted: 11/15/20 07:10am Link  |  Quote  |  Print  |  Notify Moderator

You ALWAYS wire the 120 element DIRECT to 120 power to test a CU. Just 2 wires and connect to an extension cord. Run 24 hours. IF the FREEZER does not get cold or below 10 degrees the CU is bad. IF the lower section does not get below 38 degrees the CU is bad. Now, I am not a fan of rebuilt as a Service Shop. IF they are defective they do not pay a fair labor for the shop to diag and replace the defective unit. Now, IF or you are doing the work yourself, I would go with a Rebuilt. That way, IF it is bad, you have the time to replace the defective unit. BTW, Dometic and rebuilders BOTH have replacement CU's for your model. I would never trust that so called RV shop again. Doug

PS, I don't know where that poster got his info that a defective Thermister will freeze or get extremely cold. WIVES TALE. I have yet to see a Thermister make a BAD CU freeze or get extremely cold. Yes, they can cause too low temps, but don't use that as a guideline for Diag on a cooling problem.

Old-Biscuit

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Posted: 11/15/20 12:16pm Link  |  Quote  |  Print  |  Notify Moderator

dougrainer wrote:

You ALWAYS wire the 120 element DIRECT to 120 power to test a CU. Just 2 wires and connect to an extension cord. Run 24 hours. IF the FREEZER does not get cold or below 10 degrees the CU is bad. IF the lower section does not get below 38 degrees the CU is bad. Now, I am not a fan of rebuilt as a Service Shop. IF they are defective they do not pay a fair labor for the shop to diag and replace the defective unit. Now, IF or you are doing the work yourself, I would go with a Rebuilt. That way, IF it is bad, you have the time to replace the defective unit. BTW, Dometic and rebuilders BOTH have replacement CU's for your model. I would never trust that so called RV shop again. Doug

PS, I don't know where that poster got his info that a defective Thermister will freeze or get extremely cold. WIVES TALE. I have yet to see a Thermister make a BAD CU freeze or get extremely cold. Yes, they can cause too low temps, but don't use that as a guideline for Diag on a cooling problem.


If cooling unit is functioning a bad thermistor will cause overcooling due to limp mode/bos
Unplugging thermistor leads and running fridge can help determine if cooling unit is capable of cooling.
And if it is...then replace the thermistor

If NOT...then force cool by plugging element leads in directly to outlet and run fridge
IF it gets cold...bad circuit board
IF it does NOT...bad cooling unit

But kinda mute point now cause OP has already removed cooling unit so testing of cooling unit is futile.

IAMICHABOD

Sunny So Cal 90713

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Posted: 11/15/20 12:17pm Link  |  Quote  |  Print  |  Notify Moderator

I am very interested in this thread,I see that you have a Former Rental and as of yet there has been no members of that thread that have had a failure of the refrigerator.

I will be looking for the outcome of this. I can only assume that you did not get the extended service contract.“extended warranty,” as they like to call it.


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Boon Docker

Mountain Foothills of Southern Alberta

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Posted: 11/15/20 12:41pm Link  |  Quote  |  Print  |  Notify Moderator

I think it is pretty straight forward.
If the boiler is heating properly as the OP stated and no cooling, the cooling unit is shot.

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