7 wire trailer wiring

[drewpster]

We just bought our first camper and I am not sure how to go about wiring the plug for our van. We will be towing a used late model Jayco popup with a '07 Nissan Quest. The popup has an onboard battery. I read on a Nissan website that a powered converter must be used to wire the 7 wire plug. I am starting from zero here as I have never wired a trailer for a late model vehicle. I know there are harnesses available that will plug into the factory tail lights, but I have not found any for this year Quest van. I have never used a converter to wire a trailer either. Any idea how to go about this?

 

[tashasdaddy]

Re: 7 wire trailer wiring

you may have to get the converter from Nissan.

http://www.accessconnect.com/trailer_wiring_diagram.htm

http://www.autoanything.com/towing/65A3368A0A0.aspx

 

[Silvertip]

Re: 7 wire trailer wiring

If your Quest has a separate bulb for the stop and turn signals, you need a converter. These do not have to be model-specific. If you find one, then its a matter of plugging it into the existing vehicle harness. A generic version requires tapping into the vehicle harness just as you would if you added standard wiring. Converters are required because vehicles that use a single bulb, but two filaments have different vehicle wiring. On those vehicles, the stop and turn signals use the same filament. The flasher interrupts the stop/turn circuit when the brake is applied and your are turning at the same time. The reason the converter is required is that the trailer has a dual filament bulb so that system is not compatible with the van. You can eliminate the converter however if you install separate turn signals on the trailer and run separte wires to the plug. That would require a five conductor plug however. 1) Left turn, 2) Right Turn, 3) Tail/running, 4) Stop, and 5) Ground. The seven wire receptacle on your van has one conductor with +12V on it from the vehicle battery. That line can feed the battery in the camper. Now you are up to six pins. The seventh pin in the harness would be used for back up lights if you have them, or for electric trailer brakes. The long and short of this is if you install separate turn signals you don't need the converter. If you don't, you do. You can also buy a 7-pin to four or five pin adapter that plugs into the 7-pin receptacle on the van. Your trailer then plugs into the four or 5 pin end of the adapter. The converter wires between the vehicle harness and the 7-pin receptacle.

 

[guy74]

Re: 7 wire trailer wiring

A powered converter, is a device the has it's own battery power feed, and just uses the wires to the vehicles lights to trigger relays built into the converter. With the powered converter there is no extra load on the vehicle's lighting circuits. I have retofited systems like that into older class * semi-trucks, I like the way they work, especially when towing two or more trailers. I think I've seen ones the were also for converting from seperate brake lights to combination lights, as well as keeping the trailers lighting circuit separate from the tow vehicle's. I think most newer vehicles require the powered converter to satisfy warranty issues, but that just what I remember reading somewhere.
Goodluck,
Brian

 

[drewpster]

Re: 7 wire trailer wiring

I took a closer look this afternoon while cleaning up the popup at the wiring. The 7 wire plug on the trailer is all set as the standard diagrams have shown. The camper uses surge brakes instead of electric ones so the circuit normally used for the brakes is not used but the rest of the circuits are in place.
The problem I have is figuring out the wiring for the tow vehicle, the van. Our Nissan most likely uses a ECU to control all the lights. I do not want to mess up the computer by wiring the van's 7 wire socket incorrectly. There is also the concern with the battery charging circuit. Is this circuit included in the converter? Or is a separate circuit needed from the van's battery? I do not want to attempt charging the battery through a measly 14 gauge wire. Is it a risk running a separate circuit directly from the van's charging system to the camper battery?
I found out through a Nissan forum that the van has a towing circuit located behind a panel in the back of the van. The fuse for it is located under the hood. I assume this circuit is used to power a powered converter.

 

[Mkos1980]

Re: 7 wire trailer wiring

Heres a nice diagram from eTrailer.

 

[ebry710]

Re: 7 wire trailer wiring

Mkos1980 fantastic diagram. I am impressed.

 

[Dunaruna]

Re: 7 wire trailer wiring

If your intension is to charge the trailer battery with the vehicles alternator, I would suggest you forget about the trailer plug and fit an anderson plug setup you will be able to use larger diameter cable. That way you will minimize voltage drop over such a long distance. You should also fit appropriate circuit protection and isolation. Also, check the size of the wire that nissan supply as an accessory in the rear of the vehicle, it's probably only 16 or 18 ga and will not be sufficient for your needs.

I would suggest 6mm sq (10 ga?) from the front of the vehicle to the trailer battery. Both positive and ground.

 

[ebry710]

Re: 7 wire trailer wiring

If your intension is to charge the trailer battery with the vehicles alternator, I would suggest you forget about the trailer plug and fit an anderson plug setup you will be able to use larger diameter cable. That way you will minimize voltage drop over such a long distance. You should also fit appropriate circuit protection and isolation. Also, check the size of the wire that nissan supply as an accessory in the rear of the vehicle, it's probably only 16 or 18 ga and will not be sufficient for your needs.

I would suggest 6mm sq (10 ga?) from the front of the vehicle to the trailer battery. Both positive and ground.

Dunaruna brings up an interesting point. I have always looked at a trailer battery as a remote battery and not an auxiliary battery. The difference being that an auxiliary battery is treated like a second battery, with a dual use regulator, getting full alternator charge. The remote battery getting what could be called a trickle charge with no direct regulation and no need for a thicker gauge wire. What does anyone think?

 

[gstanton]

Re: 7 wire trailer wiring

Two caveats here....

An on board battery (trailer) with electric brakes is how the electric brakes engage IF the trailer disconnects from the tow vehicle. The act of "dis-engaging" pulls a plunger that activates full 12 volts to the electric brakes on the trailer, causing it to slow down and/or stop. Something that we all want to happen, in the event of a separation.
Second, yes, the connector between the tow vehicle and the trailer is how the trailer battery gets its charge. I've used 14 gauge in a pinch, but 12 or 10 - stranded - would be better.
This is a separate wire from the trailer brake wire.

 

[Silvertip]

Re: 7 wire trailer wiring

The charging line does not pass through the converter. It must be a separte 10 ga. or heavier line directly to the battery or a junction terminal at the front of the vehicle. It should also be fitted with a circuit breaker up front. Keep in mind also that the ground wire in the standard trailer harness is probably a 12 or 14 guage which also serves as a ground for the battery on the trailer and as such is not capable of handling the load the charging wire is capable of. The ground wire must therefore be sized the same or larger than the charging line or it will get hot and melt insulation if for some reason you need to crank the van more than normal. Remember, those two batteries are in parallel so it looks like one big battery.

 

[drewpster]

Re: 7 wire trailer wiring

I finally found a supplier that carries the type 7 wire plug (tow end) that I need this make this work.

http://www.drawtite-hitches.com/fullpic.php?18321.jpg

I can tell from the picture that the flat plug is used for the lights from the converter. The other wires are used for a charging circuit for the brake battery. (not used on my popup)

The gauge of the wire does not seem to be correct for charging the onboard camper battery. (deep cycle) Is it unusual to use the tow vehicle to charge this battery? Do I need a separate circuit from the van's alt? Or should I use the plug and the smaller gauge wire as ebry710 suggests?

 

[Dunaruna]

Re: 7 wire trailer wiring

I finally found a supplier that carries the type 7 wire plug (tow end) that I need this make this work.

http://www.drawtite-hitches.com/fullpic.php?18321.jpg

I can tell from the picture that the flat plug is used for the lights from the converter. The other wires are used for a charging circuit for the brake battery. (not used on my popup)

The gauge of the wire does not seem to be correct for charging the onboard camper battery. (deep cycle) Is it unusual to use the tow vehicle to charge this battery? Do I need a separate circuit from the van's alt? Or should I use the plug and the smaller gauge wire as ebry710 suggests?

The name of the game is to reduce voltage drop. Voltage drives amps, the more voltage you can supply to the 'house' battery the better it will charge. Good quality heavy wiring and good connections are the key. Standard trailer plugs don't cut the mustard. An anderson plug is a good heavy duty positive capture device. It will not shake loose.

The breakaway electric brake unit should have it's own dedicated battery, not the 'house' battery although they can be linked for charging purposes via appropriate isolation.