Norcold nr751bb wiring HELP

Aubrey

 I was having success repairing our new-to-us 2017 T@B 400 issues when I noticed the Norcold doesnt cycle on DC power.
I removed it to check the connections and verify power from the plug, and while checking the connections I got SIDE TRACKED!
I have more spade terminals than wires on the control board. didnt realized till it was several were loose and I am not sure which goes where. I need to verify this before I proceed with diagnosis of the cooling. Im in a PINCH!
I found only one description of the wiring on a similar Norcold and the fourth tab up was not used.

Grumpy_G

The connector with the additional spade goes on the 12V +, and the thin red wire connects there. The thin red and black wires are for the fan. 

Aubrey

Well fellow boon dockers, I made my head numb with about 20 google tabs open and observed this configuration. Plugged in to DC and, nothing.
I looked at the fan a decided to blow on it to see if it was stuck, it moved.
I blew on it again with more force, moved the fan, then it started cycling and the fridge seems to be working. Was that a coincidence? I imagine there is a start up delay built in or something. I will monitor it and report. 
NOTE that the trai;ler is plugged to shore power (20amp garage outlet with dongle adapter) but the fridge is running with only DC plugged in.
I hope I can reassemble the kitchen in working order before my wife gets home!

Aubrey

All put back together and cleaned up, staying cold on both AC and DC at the 4 setting, not sure what caused the original warming issue, maybe something was a bit loose after all, resistance maybe?
I know I will take photos and notes before moving any more wires!!
This may be the last repair needed for awhile so see you in the main forum for some good time posts!

Aubrey

Thanks Grumpy G, I would like to know what each wire goes to and label my diagram for my records. Does anyone know the whole schematic?
I assume AC at top
DC next along with fan
the bottom wires look like they power the compressor
and I assume the other 2 are for thermostat, light or both?

Grumpy_G

This answers all your questions: https://www.manualslib.com/manual/1581368/Norcold-Nr740-Series.html 
The last page has a wiring diagram. 

akarjala

I bought a 2017 T@b 400 in June. The fridge wasn't working at all, so I pulled it out and disassembled/reassembled the wires similar what you did. I even pulled the circuit board to make sure nothing was burned. 

Put everything back together and it worked! 
 
But after about 4 hours, it quit working again, so I thumped the thermostat and the fan came on and it began cooling. Again, after a period of time, the fridge stopped cooling again.  This cycle kept happening until I finally replaced the thermostat.  After doing that, the fridge is working very well. Just leaving this here in case you start experiencing intermittent issues. 

Aubrey

Right on! Thanks!

Aubrey

UPDATE:
Winter is retreating and I am getting the T@B 400 ready, once again the Norcold NR751BB AC/DC fridge stopped cooling. I repeated the process of elimination with the idea that the fridge controler (pictured above) was having some sort of surge protection going on. 
Sure enough I find that if it is running on DC12v and I plugg into my shore power without turning the Battery Cut-off switch OFF
the unit stops cooling (light stays on)...
As long as I shut off the battery switch before plugging to shore it works fine.
Maybe that is recommended anyway but I dont know.
Hope this helps someone.

Denny16

The same Norcold fridge in our TaB400, works on both AC and DC without turning off the battery cutoff switch whilst connected to shorepoiwer.
 Cheers 

Aubrey

Not sure why ours sometimes quits when plugging in to shore, i do get a bit of spark at my 20amp garage outlet when plugging in sometimes. Not Hollywood sparks just a tiny snap. Non-cooling has occured a couple times in the off season at home.

Denny16

You are getting an arch at the plug, because you have a load turned on on the TaB.  Switch off your main 40-amp breaker before connecting the cable,to,the garage outlet, and it should not arc with the breaker off.  This is a good safety practice.  Whilst camping, always flip the breaker off on the camp site power pedestal, this will make connecting the TaB safer also.  You should consider getting a power surge/protection unit to out between the shore power outlet and the TaB.
 Cheers 

Aubrey

Agreed, last fall I made that my habit, turning of the battery cut-off then plugging in. Also using the breaker at 30amp posts. We have a decent surge protector but it didnt occur to me to use it at home. I will check that out today. Funny only the fridge was affected, and like i often do i ran with the first idea that came to me instead of an objective process of elimination. Derp!
At least my trailering routine is improving and that problem is solved. Thanks!
Now to figure out the portable solar and battery monitoring without redundant spending.
I have a thread on that now "solar info head spinning", getting lots of good info there.
Thanks again to all forum members for helping out the nube!