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Old 02-04-2024, 02:13 PM   #1
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Norcold N8 Fridge - diagnosis plan for your input (calling all techys)

I have been fighting a problem with the Norcold N8 Fridge in my newish RV (250 RKS with fridge mounted in the slide out so it has a side vent at the top). Basically, when it gets really really hot outside (like high 90s), the fridge will stop working after a day and half. Then it starts working again usually in the evening. Switching to propane does not solve the issue.

I noticed this when I saw that the metal fins in the back of the fridge compartment had water droplets on them (vs some light frost) and the fridge was not really cold inside.

I was amazed at how much heat comes off of the back of the fridge (even when running on shore power).

Those with my setup will know there's a small auxiliary fan mounted on the back of the fridge to cool the condenser fins. When the fridge "malfunctions" I notice this fan is NOT working, like it should be. When everything is OK with the fridge, the auxiliary fan is running.

The dealer can't duplicate the problem (because it's not hot outside) so I am going to try to diagnose this on my own. Then, hopefully, I can let the dealer know what to do (they're reasonable and I hope they'll listen to me).

ANY INPUT ON THIS WOULD BE WELCOMED!!

From the schematic diagram below (from my owner's manual)...

a) You can see the auxiliary fan "F".

b) You can also see a switch "D" (this is a little thermistor thing that is attached to the fins on the condenser and barely accessible from the top vent).

c) You can see that one side of the switch "D" (the "left" side) receives 12 VDC from terminal 6 on the control board.

d) I am assuming that when switch "D" gets hot enough, it shorts out and then provides 12 VDC to the fan. Current flows from terminal 6 on the control board, through the switch, through the fan, and then to ground (terminal 1).

Assuming that all of the above is correct...

1) When I initially power up the fridge, I am assuming I should see 12 VDC at terminal 6.

2) i should also see 12 VDC across switch "D".

My reasoning is that if switch "D" is used to power up the fan, I am assuming the control board is not deciding when to energize terminal 6 - it should be hot all the time.

3) When the fan "F" starts working, I should see 0 VDC across the switch "D", and I should see 12 VDC to ground on each side of the switch.

My reasoning is that if "F" is now a short circuit, there's no voltage drop - it's basically a piece of wire.

4) When the fridge malfunctions and the fan is off...

4a) I will need to verify that I still have 12 VDC at terminal 6. If I don't, then something's wrong with the control board. Assuming this test is passed...

4b1) If I see 12 VDC across switch "D", then switch "D" is defective since it should not be open circuited.

4b2) I could test this theory by jumpering across switch "D" and seeing if the fridge starts working again.

4c1) If I see 0 VDC across switch "D" AND I have 12 VDC to ground on the "right" side of the switch, it means that the fan is bad because it is not working despite being powered by 12 VDC.

If I had to guess, I would say that the switch "D" is bad. I can't see how the fan would intermittently stop working...and if it did, I assume it would eventually melt because it would still be getting voltage.

I would appreciate any help here...
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Old 02-04-2024, 02:34 PM   #2
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Do some searches on these fridges and fans. There are some good writeups about adding more or bigger fans and switches or theroswitches.
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Old 02-04-2024, 02:39 PM   #3
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Switch 'D' is a thermostat that CLOSES when Fin temp reaches 130*F
When closed is allows 12VDC to fan starting it so more air flows across the condenser fins

Switch 'D' OPENS when FIN temp reaches 115*F stopping 12VDC to fan shutting it down

Terminal 6 should have 12VDC whenever fridge is ON

12VDC would be at Input side of Switch 'D' when Open and Closed
12VDC would be at Output side of Switch 'D' when it Closes
*it is a thermostat which is just a switch that opens/closes based on temp set points. 12VDC would be on both sides when closed and input side when open

Fan only gets 12VDC when Thermostat on Fin closes based on FIN Temp


SO..........
Fridge ON
12VDC at terminal 6
12VDC at Input of Switch 'D'
12VDC at Output of Switch 'D' when it Closes
12VDC at Fan when Switch 'D' closes
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Old 02-04-2024, 03:38 PM   #4
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Thanks guys - it sounds like my understanding of the circuitry is correct. I will prost an update when I do the testing.

I did install an auxiliary fan in the upper vent. I think that might solve the whole problem, but the problem with the OE setup is bugging me and I can't leave well enough alone. I did not mention the auxiliary fan kit so as not to muddy the waters but I do appreciate you mentioning that!!

Thanks for the responses and for taking the time to read the post.
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Old 02-05-2024, 11:39 AM   #5
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Quote:
Originally Posted by STDevil View Post

ANY INPUT ON THIS WOULD BE WELCOMED!!

I would appreciate any help here...

Please confirm that you do not have an ARP Fridge Defender installed.

If the thermal snap switch for the OEM cooling fan doesn't see enough heat, it won't close and turn on the fan. When the fridge malfunctions and stop cooling, it might just be it isn't generating enough heat back there.

Our fridge in our '19 24RKS performed a bit like yours at one time. No codes shown, it just got (more) lazy at cooling when the weather got hot and sometimes again even when it wasn't all that hot. I couldn't figure it out. On a whim, I took our spare control board and swapped it out. Problem solved, it was working correctly again (up until that board failed too). I think we're on our 6th board now. We were on the 3rd board by the end of the 1st year of ownership.

Get a spare control board and try swapping it out. If you have an N8 Norcold fridge, think of like a spare tire, you know it's just a matter of time before you'll end up needed it. They're usually around $130 on Amazon. >> https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

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Old 02-05-2024, 03:34 PM   #6
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Hi - no I do not have a defender.

I was wondering about the board. I did not know if there was something else on the board that could stop the fridge from working.

Regarding the control board, I have a different model board on mine...see attached image.

Everything on the interwebs points me to the board you shared, but I wondered if anyone knew if my specific model number is required.

I am going to install a new board and see if that helps - after seeing what's going on with the thermistor thingy...

Thank you again for chiming in.
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Old 02-05-2024, 04:02 PM   #7
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Quote:
Originally Posted by STDevil View Post

Everything on the interwebs points me to the board you shared, but I wondered if anyone knew if my specific model number is required.

I am going to install a new board and see if that helps - after seeing what's going on with the thermistor thingy...
Yes, I can see your board is different than ours. And more expensive to purchase. Wonder when they made the change?

I >think, not completely sure< when the thermister is unplugged, the fridge goes into full on cooling mode. But, it should throw a code when unplugged. That could be the first step to check. You should be able to find a resistance chart online for testing your thermister. Should be in a Norcold's service manual.

By chance, does your thermister become encrusted in frost/ice over time? Ours does. And if it does, that'll fool the thermister into thinking it's super cold inside the fridge, telling the board to not bother cooling. Time to defrost when that happens.
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Old 02-05-2024, 10:48 PM   #8
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Hi. I think you may be referring to the thermistor on the inside of the fridge compartment, on the fins that get cold. Unplugging this does not help my situation.

I am referring to the thermistor that is on the condenser fins that are on the outside of the fridge. This is what is used to control the fan that's on the outside of the fridge, which blows on the condenser fins.

I will contact Norcold tomorrow to see what they have to say about this. There has to be someone there who knows something...
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Old 02-05-2024, 11:09 PM   #9
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Quote:
Originally Posted by STDevil View Post
Hi. I think you may be referring to the thermistor on the inside of the fridge compartment, on the fins that get cold. Unplugging this does not help my situation.

I am referring to the thermistor that is on the condenser fins that are on the outside of the fridge. This is what is used to control the fan that's on the outside of the fridge, which blows on the condenser fins.

I will contact Norcold tomorrow to see what they have to say about this. There has to be someone there who knows something...
Get out your voltmeter and test the DC circuit as I outlined in my post above

And it is a thermostat...snap disc
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Old 02-07-2024, 11:33 AM   #10
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Hello - I will definitely do this the next time I am out in the RV.
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Old 02-08-2024, 08:45 PM   #11
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If you determine it's a board problem, I suggest you contact Dinosaur Electronics directly for a board replacement. This company has made a living on manufacturing and selling high quality boards in lieu of original factory boards.

Mike
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Old 02-09-2024, 06:15 AM   #12
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If you determine it's a board problem, I suggest you contact Dinosaur Electronics directly for a board replacement. This company has made a living on manufacturing and selling high quality boards in lieu of original factory boards.

Mike
I second that. Replaced the board on my MH, no problems after. Their prices were very fair, at least several years ago, compared to the dealership.
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Old 02-10-2024, 07:32 AM   #13
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I second that. Replaced the board on my MH, no problems after. Their prices were very fair, at least several years ago, compared to the dealership.
According to the website at Dinosaur Electronics, their boards are manufactured in the USA at a plant in Oregon. The boards are manufactured to higher standards than the boards made by Atwood/Dometic, Suburban and Norcold.

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Old 02-19-2024, 11:16 AM   #14
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Thanks for the lead on the Dino Boards. It looks like they sell through distributors only, and you need the get the number off of the back of the board. So I am going to go get all the numbers today and then see who I can source a board from.

I will keep everyone posted!
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