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Old 06-07-2018, 11:42 PM   #1
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How to wire fridge to tow vehicle via wiring socket?

Bought a Norcold N3104 3 way fridge and am stuck on how to connect the wiring for 12V use (both with tow vehicle while driving and from trailer battery when parked). Hoping someone has connected something like this before and can walk me through it.

Here is the wiring adapter on the back of the fridge along with the wiring diagram from Norcold.
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I have a 7 pin round wiring socket and I believe this is the wiring diagram for it.
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The part I am most confused by is the HC+/HC-/D+ connections. Are these standard and already wired into the wiring socket from my tow vehicle? If so, which pins do I connect the wiring from the fridge to? If not, is this something than can be wired into the wiring socket from the tow vehicle or does it need its own set of wires?

Thanks for any help.
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Old 06-08-2018, 06:08 AM   #2
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Unfortunately, the resolution on your Norcold schematic is too low for me to read. Can you post a higher res version? I do not think the wiring will be that difficult.

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Old 06-08-2018, 06:23 AM   #3
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Ok so here goes,
LC+ and LC- go to the trailer + and - connection
HC+ goes to the blue aux circuit
HC- goes to the white ground circuit
D+ goes to a 12 volt hot (only when the truck is running) or if you run you clearance light while traveling you can wire it to the black “clearance marker lights”
If you wire it there the fridge will run off the truck when lights are on and off the trailer if lights are off.
Hope this helps some

All of those wires except an 12volt ignition hot can be found inside the trailer in the 12 volt 7 pin distribution box on late model trailers. Not for sure on a 1970.
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Old 06-08-2018, 06:30 AM   #4
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If you wired the D+ to the red stop light circuit The refrigerator would run off the trailer battery while going down the road and off the truck battery when the brake pedal was depressed.
The D+ wire is a sensor wire the tell the fridge the TV is present and running to prevent the fridge from running your TV battery dead if off and not unplugged.
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Old 06-08-2018, 06:53 AM   #5
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Old 06-08-2018, 07:08 AM   #6
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Most, if not all modern TV's have a relay which disconnects the "charge line" when the key is off.
Check to see if this is the case with your TV.
If so D+ can be connected to the charge line along with the + from the TV.
As long as you don't leave the key on for long periods without the engine running you should be OK. IMHO
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Old 06-08-2018, 08:08 AM   #7
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TomW. Sorry for the low res photo. Here is a link to the PDF

https://www.thetford.com/wp-content/...ler-Wiring.pdf
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Old 06-08-2018, 08:16 AM   #8
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GMFL. So helpful. Thanks so much. My plug is wired as was in 1970 so have to do some checking to see if matches the attached wiring diagram. Hoping it is.

Can you give advice about what gauge wire is needed for each? Have read maybe 8 or 10 AWG.
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Old 06-08-2018, 08:37 AM   #9
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Depends on the distance from tv battery, installtion manual should cover it.
Uses 15.8 amps from what I see.
https://www.engineeringtoolbox.com/a...uge-d_730.html
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Old 06-08-2018, 09:54 AM   #10
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I used to own a Hi-Lo trailer that had a 3 way fridge. When set to battery the fridge took power exclusively from the trailer battery. While I was driving, the vehicle would send voltage to the battery via the bargeman plug. All worked well until time took its toll on the connection between the trailer plug and the bargeman socket. In many cases I found that I arrived at a campground only to find my battery dead. The main problem was that the Hi-Lo's hydraulic lift system was 12 volt powered. So for all intents we either had to plug the trailer into a 110 volt outlet and wait for sufficient charge to raise the trailer, or I had to unhitch and jump start connect the tow vehicle battery to the trailer battery.

Bottom line I looked at the plug on the trailer and found that the terminal that carried 12 volt power had a very thin layer of green corrosion on the copper blade. That was reducing the voltage available to charge the battery. From that point on I used to used a can of spray electrical contact cleaner and would spray that contact prior to plugging into the tow vehicle receptacle.

Keep in mind that technically you should be able to operate from the trailer battery, provided that your tow vehicle is wired to provide a 12 volt charging circuit and the wire size is adequate to transfer enough power to keep that battery charged. Refrigerators take a lot of amperage in 12 volt mode to operate that heater and in my opinion are really only to be used while a source of power is available to keep that battery charged. Don't try to get charging power from an existing vehicle wire that is serving another electrical function. Typically that 12 volt wire is dedicated for supplying power only and runs from an independent fused position on the vehicle terminal board.

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Old 06-08-2018, 10:22 AM   #11
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Fill your freezer a day or two before you leave, and stop and buy a bag of ice for the fridge at the start of your journey. 12 volt is a good backup, but hard on batteries. I only have a 2 way, but can keep both the freezer and fridge plenty cold for several hours of travel daily (six hours a day is my limit with a couple of breaks where I do turn the propane on in the fridge).

If I am going to a rally... then I buy the food at or near my destination.
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Old 06-08-2018, 10:29 AM   #12
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Quote:
Originally Posted by GMFL View Post
If you wired the D+ to the red stop light circuit The refrigerator would run off the trailer battery while going down the road and off the truck battery when the brake pedal was depressed.
The D+ wire is a sensor wire the tell the fridge the TV is present and running to prevent the fridge from running your TV battery dead if off and not unplugged.
"red stop light circuit" should be the "red running light circuit" else the fridge would ONLY run when you are braking the rig...this means you should drive with tow vehicle running lights ON, as many of us do anyway...My AS rear and side view cameras are powered this way...
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Old 06-08-2018, 02:39 PM   #13
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N3104

12V/DC 16.2A
120V/AC 1.8A

That's a lot of current. Why can't you use gas for the fridge when travelling?

pg
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Old 06-09-2018, 11:06 PM   #14
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AlinCal. Thanks for that table, going to have to go lower gauge than had anticpated.

jcanavera. Thanks for the advice. Will add that spray electric contact cleaner to the supply box.

Foiled Again and pgellar. Valid points. Have never had a 3 way and was intending on buying another 2 way but this is the way it ended up. If we have the 3 way, then might as well have use of all of its capabilities. Have the skins partially off as am remodeling so no better time than now to get the wires in place.
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Old 06-10-2018, 07:37 AM   #15
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We used to have a camper with a 3 way fridge and would travel on 12v mainly because the pilot would blow out and it did not have auto ignition, this was discovered after traveling for some hours in the desert heat. The truck had a diesel engine with 2 batteries and a high output alternator so as long as you were running things were fine, did not cool as well on 12v compared to being on propane though(when lit) as I recall.
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Old 06-10-2018, 11:33 PM   #16
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AlinCal. That table you provided...does that apply to the gauge of wire needed for HC+ (blue aux) or does it apply to all the wires?
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Old 06-11-2018, 07:48 AM   #17
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The load for each wire needs to be considered but the HC+ and the HC- need to be the big ones.
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Old 06-17-2018, 09:59 AM   #18
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I have a Norcold 3-way

When I installed my Norcold a year ago, the instructions that came with it indicated to solder the fridge's heater wire to the 12 volt wire used to power the electronics. I did that and it works, drawing power from the house batteries. Like the other posts, this will drain the house batteries if the tow vehicle isn't running and recharging them. I have been worried about the gauge of wires used by Nissan on the tow package but have not had any problems so far. However, I've noticed that the drain on the house batteries is from the first one in parallel (I think there has been a thread on this wiring configuration). So, I am considering a separate heavy gauge wire from the fridge to an ACC connection on the Nissan so that the fridge only has 12 volt power to the heater when the engine is running.
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Old 06-18-2018, 05:09 AM   #19
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Thanks for posting, great information
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Old 06-19-2018, 02:38 PM   #20
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Forrest. Don't recall reading anything about soldering in user manual for this Norcold. And if that was needed, would need to step up skills to accomplish.

Alan. Thanks again. Just can't get Norcold or Autoplicity or local trailer shops to respond and the manual fails to specify gauge of wire needed or amps through each circuit...so here is the plan.

Going with 8 AWG wire for all 5 connections. Have some spare from prior shore connect plug so no additional cost. Don't want to wonder down the road if the wires are melting so thought this would be worry free route. Will wire as you indicated.

Going to put the LC+ and HC+ on switches at fridge so can avoid draining any batteries by accident.
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