Norcold shutting off - Fixed!

The Norcold N621L in our camper has worked relatively well since new for the past 12 years. After returning from a trip in July we left the fridge on while plugged in inside the shop. We left some condiments and drinks in there but nothing important. Things were fine until about a week ago when we wanted some ice cream that we had put in the freezer some time before. It was soft and melting and the fridge was warm. The LED indicated it was still on 'auto' but I noticed the interior light was not on and wouldn't come on after closing/opening door again.

So I powered it off and back on and the light started working and the fridge started back up. I tried LP mode and it lit up immediately and then I switched back to auto which chose AC. Using the diagnostic mode showed everything normal except it had saved something like 4-5 completely different error codes. I cleared those and left it running. Later that night it was cooling nicely and the next night I checked again and the Otter Pops were refrozen.

Skip forward about a week to today when I load the camper on the truck for this coming week's camping. It's totally warm again, shows an 'r' on the LED (center and lower left segments) which is not any legitimate code that I can tell. So I power cycled it again and read the diagnostic codes: "AC relay stuck closed" which is quite likely bogus as it would only cause 100% duty cycle cooling anyway. Now about 3 hours later the freezer is down to 5 degrees and all is well again. The 5-night camp trip is gonna take babysitting this thing plus coolers as a backup.

At this point I'm thinking loose connection, failing control board or maybe something else on 12V power making noise on the line. The camper's been plugged in as usual with a PD9245 onboard. It's tough to debug when it works fine after power cycling. Anyone else have this kind of random flakiness with their Norcold?

Update - Added a post where I replaced the relay and all seems well...for now at least. :)

ScottG
Nomad
Aug 26, 2018
Mine seemed to lose cooling for a short period last time we camped but I think maybe it was just going through a defrost cycle. Wonder how long a defrost cycle is?
Maybe that's what yours was doing?
wnjj
Explorer II
Aug 26, 2018
ScottG wrote:
Mine seemed to lose cooling for a short period last time we camped but I think maybe it was just going through a defrost cycle. Wonder how long a defrost cycle is?
Maybe that's what yours was doing?

It it were a short time I would consider that but it had clearly been off for many hours or days the second time with the temps in the 50-60's inside and popsicles were 100% liquid. I think I was only lucky that I caught it within hours the first time.

The most telling thing is the interior light that wouldn't work until I power cycled it. That seems like confused control logic.

Thanks for the input.
PaulJ2
Explorer
Aug 26, 2018
The way it's acting i would say the AC relay is stuck open. It does sound like a faulty relay. Maybe burned, dirty contacts.
That relay has to switch a 300 watt load on and off.
dougrainer
Nomad
Aug 26, 2018
I believe ANY type operation error code like a AC relay stuck, would shut down operation. Doug
newman_fulltime
Explorer II
Aug 26, 2018
Sounds like it cycles into defrost mode gets stuck and shuts down
dougrainer
Nomad
Aug 26, 2018
ScottG wrote:
Mine seemed to lose cooling for a short period last time we camped but I think maybe it was just going through a defrost cycle. Wonder how long a defrost cycle is?
Maybe that's what yours was doing?

The Defrost cycle happens every 48 to 54 hours when left ON constantly. It shuts the refer OFF for about 2 hours and then restarts. There is NO indication of this on the controls. Since it happens every 48 to 54 hours I do not know if the display goes dead or not. To STOP the defrost cycle is easy. Just turn the refer ON and OFF once a day and the timer restarts. Doug
dougrainer
Nomad
Aug 26, 2018
PaulJ2 wrote:
The way it's acting i would say the AC relay is stuck open. It does sound like a faulty relay. Maybe burned, dirty contacts.
That relay has to switch a 300 watt load on and off.

And if you have a relay fault code, even intermittent, you need to replace the rear Main control board. The relay's should NEVER malfunction. Doug
Happytraveler
Explorer
Aug 26, 2018
I've had it with our 15 year old Norcold. One year ago it was playing games with us and had it fixed. Last week it was doing the same thing and we ended up loosing most of our food. Our motorhome is in the shop now and we opt not getting it repaired again, we are buying a new Fridge. Yikes, cost and labor for a small fridge $2400.00.
wnjj
Explorer II
Aug 26, 2018
While it’s still empty, I’ll let it run for 48-54 hours and then check on it again. If it is the AC relay, possibly aggravated by the defrost cycle, our 5 day trip should help prove that since we’ll be on propane the whole time. If the relay is the issue I’ll replace just it (I know it’s soldered), otherwise a Dinosaur board is likely on the list.

About the ‘r’ code. For some reason I didn’t see that in my service manual but when I looked online just now it says ‘r’ is indeed AC relay stuck closed which matches what the diag mode segment said. Looks like it is the relay not opening when either the set point is reached or defrost is called for and then the fridge shuts down.

Thanks a bunch for the comments and suggestions.
wnjj
Explorer II
Aug 26, 2018
One other thing: If the relay sticks closed, doesn’t that mean it should stay cold? The wiring diagram shows the power cord, a fuse and that relay to the AC element. I can understand the board detecting AC when it’s not calling for it and faulting but if it can’t shut anything down, why is it warm? Maybe the controller faults and then the relay randomly opens some time later?