Power (Current) Via 7 Pin Connector (2017 w/ tow package)

I have been reading through the owner's manual, trying to find out how much current is available via the 12V pin of the 7pin connector.

Discussion has come up in other areas about running a 3 way fridge off of DC power while towing a travel trailer. I posit this is not a good idea, at least for most vehicles, since the fridge on DC will draw something like 13A, and a lot of cars won't be able to provide that much.

I can't find how much power is available on a 2017 V6 with the towing package. Has anyone found documentation of this anywhere?

 

No idea what they are rated for, but the aftermarket kits to add a Tekonsha P3 Brake controller to a Tacoma put a 40 amp fuse on the 10 gauge wire feeding the 12 V pin on the 7 Pin connector. 10 Ga wire should handle 30 Amps safely for runs of 50 ft or less. Since the run in a Tacoma is probably than 20 ft the wire will safely handle that.

Voltage Drop is another consideration, If you are pulling 15 Amps through 10 Ga copper wire for a distance of 20 feet, you'll lose about 0.6 volts getting to the trailer connector on your truck (assuming all of your connections are in excellent shape). You'll lose more for the run over the wiring in your trailer. Not knowing the length and gauge of the wire in your trailer, I can't calculate that. I also have no idea what minimum voltage is required to run the fridge.

I'd guess if the wire run is short in the trailer, uses appropriately sized wire, and all the connections are clean you should be fine when the engine is running at decent RPMs - so your alternator is putting out 14+ volts. However, this is all theoretical. I'll defer to those with more real-world experience.

Another thing to keep in mind: Many tow vehicles are wired so the power wire to the 7 pin connector is always hot, regardless of whether the truck is running or not. Be careful about leaving your trailer connected when the truck is shut off: 13 amps to run the fridge (plus whatever other loads are active) is going to suck your battery down over time. You don't want to come back to a truck that won't start. (If you do drain your truck battery and need a jump, disconnect the trailer wire - you'll have an easier time jumping a dead battery without that load.)

 

The current is set by the Brake Controller. It depends upon the Controller and how many wheels (brakes) the controller has to energize. Some of the controllers for really heavy trailers can do 6 wheels, some of the cheaper ones do less. My controller can do 6 wheels, asked for a 30A breaker, and 10AWG wire. I only needed 2 wheels worth, so I wired it with 12AWG and used a 10A breaker. That saved a LOT of money.

Interestingly enough, my 2014 has a fuse marked "Tow" in the stock (engine compartment) fuse box that is fused at 30A. That circuit enters the driver's compartment on a solid Gray wire that ends right at the driver's left knee cap.

 

Where are you coming up with 13 amps? The last time I looked at rv fridges they pulled 2-4a.

 

The brake controller sets the voltage (and thus the current) for the brake wire. There is a separate pin on a 7 pin connector that is just connected directly to the battery (through a fuse or breaker). The brake controller has nothing to do with this wire. It's used for charging a camper battery or powering other loads (such as the fridge the OP mentioned).

Was that a fairly heavy gauge wire (10 or 12 ga?) Did your truck come with the factory tow package or not? My 2009 did not, but I'm adding things to duplicate that package. I wonder if I've got that wire. Any tips on finding it? Is it connected to the towing connector that's in the same area? There's a lot of stuff behind that kick panel near the driver's left kneecap.

 

Compressor fridges like the ones made by ARB, etc for vehicle use pull 2-4 amps like you’re thinking.
Absorption fridges like 3-way rv fridges use way more power, which in 12v mode draws down a battery real quick

 

The always-on 12V pin is a small gauge wire, 18 gauge max. The fattest wire is the common ground for all other pins and I doubt it's even 10 gauge, maybe 12.

This wire can run a few lights and provide a trickle charge to your trailer battery but it won't flow near enough to run a fridge.

 

I'd say I'll have to look into it, but it would be a lie. I sold my last camper 3-4 years ago and likely won't buy another, so I'll take your word for it Going from memory, we usually ran the fridge while we were towing, and using the stock wiring on the trucks. We always arrived with a cold fridge(at least the food and beer was cold) and a fully topped off camper battery, then switched to propane. So whatever gauge the truck wiring was (12 maybe?) was enough to keep the fridge going without blowing a fuse. Going from that, wires are maxed at 10a if they're actually 12g. You would need 10ga wiring to be safely in the teens.

The fridge itself should be pulling directly from the trailer battery and the truck/trailer wiring just feeds the battery. You could likely run a heavier cable front to back and have a cleaner run with less drop but I don't know if you would see a real difference.

 

As a matter of fact, on my 2014 you can pull off the "hidden drawer" as if to access the interior fuse panel and there it is. White connector body with four wires, Red, Black, Blue and Gray. Blue (18AWG) is from the brake lamp switch and can be used to trigger the Brake Controller. Gray (14AWG) is directly from the 30A fuse in the engine compartment fuse box.

Hope this helps.

 

I think that's the pigtail to install a brake controller!

 

Just an FYI but I think most newer trucks with a factory tow package has the power pin on the 7 pin activated by the ignition. Therefore leaving something plugged in should not drain the start battery. I am newish to Tacomas so if wrong somebody please chime in.

 

I had read where the 12v hot to the 7 way was 10 gauge to provide 30amp service to the towed vehicle battery system. It is switched via the tow system relay under the hood. I tapped in to that line for my air bag compressor system and use the 7 way to feed the battery on my truck camper. I did blow the tow circuit 40 amp fuse recently on a camp out and I believe it happened when the compressor kicked on while the 3 way fridge was in the 12 volt chill cycle. I just avoid using 12 volt for the fridge as propane and shore power are much more efficient chilling the 3way fridge. I will be running a 8 gauge 60 amp breaker feed straight to the camper soon to set it up right!

 

That would be the best way to run the accessory power. I don't have the factory tow package, so don't know if that's how they actually did it. I've only seen one aftermarket installation done that way. I have seen owner-installed systems that included a manual disconnect switch. I think that was more for the idea of preventing a short in a damaged or corroded 7-way plug from draining the battery when the connector was not in use. If you are worried about the trailer draining things, it's easier to disconnect the plug than it was to pop the hood and flip the manual switch.

An argument can be made that activating the brake wire via the ignition switch is not the best way to go: connecting it (and your brake controller) directly to the battery still gives you battery power to the trailer brakes in the event of a vehicle electrical failure. The likelihood of ever actually needing that is probably slim. (Only once in my 40 years of driving have I ever had the vehicle electrical system totally conk out while I was in motion - that was fun: on the highway, in the rain, at night. Fortunately, no trailer).

 

I am not even sure what you are thinking let alone trying to explain.

If you lose vehicle power you lose the trigger (brake light circuit triggers the brake controller) for the trailer brakes. While controllers like the P3 have gyro’s I am of the belief that the brake trigger is needed before even the proportional aspect of the brake controller is activated. Otherwise you could have the gyro activating the brakes under deceleration due to engine braking or other situations when the brakes aren’t on.

If I am completely missing your thought process can you fill in what you are actually suggesting as I can’t see a situation where I need or could use trailer brakes when I didn’t have ignition power. The ONLY situation I can think of is loss of ignition power and you try to use the manual option on your brake controller if you wired it direct to the battery.

 

Yes, you do need the break trigger wire for automatic application of the trailer brakes. If you lose the brake control trigger (as you would if you lost vehicle power), you still have the manual brake lever on the controller.

 

Most RV 3-way fridges are 'absorption' systems. The electric heating element used draws 160W of power, either on 12V or 120V AC. At 13V, closer to what voltage would be coming from the alternator, that's 12.3A of current.

Compressor type fridges, like the chest units that are popular, run around as low as 45-ish watts, which would be 4A or so.

 

Any idea how much power they draw when running on Propane? I assume they still need something to operate the thermostat or some other controls or ??

 

40 amp fuse Batt CHG, powered when ignition is on.

 

I will be installing a battery monitor on my camper this weekend. I will shut off all other systems and take a reading running the fridge on propane. The owners manual fell short of having the specs on mode consumptions. I was surprised by the info found in the link below as to how long a 20lb LP tank could power a 3 way fridge.

http://www.campertrailers.org/3-way_fridge.htm