RESOLVED: T@B 320S not getting power from the tow vehicle

GibW

2017 T@B 320 S.  Not receiving a charge when hooked up to the TV’s 7-pin. Tested the TV with a multimeter and all is good there. 7-pin plugs are clean. Battery cutoff is turned on and battery fuse is good. Tested fuse holder as directed by dealer with multimeter and showing a charge on the battery side but nothing on the other side. Checked the junction box under the trailer and all looks good.  Thoughts for trouble shooting?

Resolution... I took the trailer to our dealer, Elk River RV (MN). They found an intermittent short in a fuse holder on the 12V power line coming from the TV's battery. They replaced the fuse holder and now it works. Also, learned that the TV's lights must be on in order for the TV to deliver 13.7 volts for charging. A shout out to the crew at Elk River - they provided EXCELLENT service, working us in to their already booked schedule. We are so glad we bought our T@B from them. Thanks also to all on the forum and T@B Facebook page who weighed in with diagnostics/solutions.

Sharon_is_SAM

Looks like the TaB 7 pin cable is at fault.  Sometimes the pins can bend just slightly enough to prevent contact.  Check out the 12 V pin at 11:00.

GibW

Sharon_is_SAM...Thx.  Will do

ScottG

Bumping this just to call attention to the edited original post which describes the resolution. Thanks for the followup, GibW!

lkc001

Post this as another good dealer to do business with!

Bayliss

@GibW, it seems odd that your tow vehicle lights must be "on" for it to deliver 13.7v to charge the trailer battery.  Did your dealer provide any explanation as to why that is?  I don't turn on my lights on my 2007 Toyota Tundra while towing and it seems to charge my camper battery fine.  Glad you resolved the issue.  Thanks!  (Greg) 

Marceline

Bayliss said:

@GibW, it seems odd that your tow vehicle lights must be "on" for it to deliver 13.7v to charge the trailer battery.  Did your dealer provide any explanation as to why that is?  I don't turn on my lights on my 2007 Toyota Tundra while towing and it seems to charge my camper battery fine.  Glad you resolved the issue.  Thanks!  (Greg) 

My understanding is that the tow vehicle’s alternator output may be controlled by an onboard computer, and that computer will order a higher output when the vehicle’s headlights are turned on. But this may be specific to certain vehicles. 

GibW

Exactly. Many of today's autos have "smart" alternators that only produce a charge when sensors tell it that it's needed. This is intended to save fuel and enhance efficiency. This is what happens with our Kia. When the engine is running and lights are off, the charge line only shows 12.5 or 12.6 volts or the amount of charge in the vehicle's battery. But when the lights are on, the charge line shows 13.7 volts. My understanding is that many trucks do not have this feature as fuel efficiency is less of an issue but I would also guess that this may be changing especially with the new breed of mid-size pickups.

davel4wa

A short in a fuse holder is it's normal state, by the way. What you had was an intermittent open. Wouldn't it be nice if dealer personnel would inspire us with their knowledge and correct use of terminology. 

davel4wa

Alternators in automobiles have built in voltage regulators and have for decades. It is the job of the regulator to keep the output voltage of the alternator at the proper level by varying the exciter current in the alternator. At idle speeds it's not uncommon for the voltage to be close to the static battery voltage. As the engine speed increases or as the electrical load increases the alternator output voltage will increase to a level sufficient to keep the battery charged and supply current to the load. There is nothing special about this. What some vehicles have, particularly those equipped for towing, is a relay that controls the power supplies to the towing harness.

Art

Having a relay in the trailer towing circuit is the proper way to insure you will never drain the TV battery when it is not running.

GrandmasKid

I've been struggling with this and am just now seeing that having my lights on might make a difference in my TV output and can't wait to try it tomorrow morning. I have a relay little box on the charge line but I don't really understand it. Can it be thought of as a one way valve for the current flow? We tow with a Toyota Highlander Hybrid and I have been told that they are finicky with their power management and are not really made for towing. We've towed our T@B with it over 22,000 miles over the last two years with great success except for the refrigerator depleting our 92 amp hour AGM battery. The refrigerator on battery, the heater noise at altitude, and the cushions too firm, are the only disappointments with our 2017 T@B Outback so far. Don't get me wrong we are enjoying our T@B after 40 years of tent camping. It is much more comfortable. If anyone has suggestions on any of our issues I'd love to hear them.
 

GibW

Another, or perhaps the last, option would be a dc to dc charger. Ours seems to be working now, but I've given these some thought. Here's a link to some at eTrailers.com... https://www.etrailer.com/search/Dc+To+Dc+Battery+Charger

JEB

This is interesting. I was not aware that turning on the lights might make a difference.  Doing some sleuthing on the Chevy Colorado and its GMC Canyon twin, it does make a difference. There are in fact two ways to increase voltage to the trailer battery when towing with these light trucks: (1) activate tow/haul mode; or (2) turn on the lights if the vehicle has no tow/haul mode or the trailer is too light to use it.  From page 230 of the 2019 Colorado owners manual:

“To help charge a remote (non-vehicle) battery, press the Tow/ Haul Mode button on the center stack. If the trailer is too light for Tow/Haul Mode, turn on the headlamps to help charge the battery.“

Cbusguy

I put a renogy dc to dc charger on my trailer battery, heavier alternator and ran 2 gage wire to a seperate high amperage anderson connector.      

Zero problems maintaining a charged trailer battery.

Luck favors the prepared.

RollingBnB

I installed a 200w inverter under the sink so I run the fridge on 120v ac while driving. Works much better than the 12v side of the fridge.

lkc001

I have a 2016 Nissan Frontier SV 4x4--I have to run with headlights on or I don't have running lights, brake, or turn signals on my trailer.  At first, I thought I had a wiring problem, but it is just how my specific vehicle is set-up with the tow package.  Other tow vehicles I have owned have not required the headlights to be on when towing.  

ScottG

@lkc001, I have the 2015 version of the same truck--I'm pretty sure my headlights don't have to be on for my trailer brake and blinkers to work, but now you've got me wondering so I'm going to double check.

If that is the case, than something is definitely wired incorrectly, as such a configuration would make for a very dangerous circumstance. There should be no way to disable--even inadvertently--your brake lights and turn signals.

Do you have the Nissan OEM tow package?

ScottG

UPDATE: Just to be sure I checked this out on my Frontier. While--as expected--the tail and side marker lights are linked to the headlights, the brake and turn signals operate regardless of whether the headlights are on or off.

GrandmasKid

I just read that Toyota Highlander and Camry Hybrids don't have alternators. I just decided to buy a multimeter and a battery booster. I'm determined to get to the bottom of this and be able to boost myself out of camp if necessary.

"In a hybrid, the engines are off some of the time, the brakes are regenerative, saving pad & rotor life, there is no transmission fluid under load, there are no starters, alternators or belts to be replaced." Mark Jacobson Toyota

lkc001

@ScottG well, now I am curios--I never knew that

One of the last things I do before taking off is to turn on the headlights then walk around and  double check tail lights, brakes, turn signals, etc.  Since I found out my headlights had to be on the check tail lights, I just assumed they had to be on for everything else to work as well.  I'll have to check whether my brake and turn signals work without the headlights on.  

Yes--I have the factory OEM tow package. 

ScottG

@lkc001, I do the same thing you do--check everything with headlights on. That's why I didn't want to insist I was correct without actually double-checking.

I'll bet a nickel yours works the same as mine (also with OEM tow), but if it isn't I would get it corrected ASAP. Realistically, it's just too easy to forget to turn your headlights on every single time you start up and drive off.

lkc001

@ScottG. I will be checking it out this weekend before I move the trailer to it's winter parking spot in the back yard. I didn't know that's how it was supposed to work so I'm sure you are correct. Haven't had any issue at all with my frontier & tows great- plenty of power & absolutely no sway.  I just love my truck 😍

WilliamA

Most, if not all, modern TV's use an isolation relay to control trailer lights. This is because the old school "hook it into the taillight circuit" either dies not provide enough power (amperage) OR the BCM monitors lighting amperage and will set a code if it is too high. The trailer light power relay gets all power for lights on a separate line that goes off with ignition off. If that power supply feed is not on an "ignition on=hot" circuit but rather a "lights on= hot" source, you will not have any trailer lights unless the headlights are on. Either that circuit is misplaced or the BCM is not sensing enough amperage draw to turn it on. 

WilliamA 

TabulatorJim

In getting our 2018 Tab 320S ready for the season, our left back turn signal and brake light did not work. As the countdown to travel was on and we sought forum advice, we assumed it may need replacing, we ordered a new one, the Kaper II L15-0021 Red LED Trailer Turn Light, from Amazon. 

Preparations were made and further tests conducted. Taking the old one apart and checking it for rust and loose wires, it looked as if replacing this may not prove difficult.

While waiting for its arrival, we sought advice from someone we trusted. We took our unit to Sunwest RV Centre here in Courtenay on Vancouver Island, where we purchased this, and spoke with Erik Vierstra, the service warranty advisor. He went over a series of procedures to see if we could isolate the problem. In order, he is what happened:

1. As the tow vehicle lights all worked, he advised tracking the problem from this on back. He tested the brake/light connector. No problem was found.

2. Next, Erik recommended using dielectric grease (as was suggested by ericnliz in 2017) on the brake pins. I purchased a very small tube of this from Lordco Auto Parts and applied this using Q-tips without success.

3. Just prior to travel, the replacement light arrived and there was no time to install this. As a last ditch effort, I decided to give the dielectric grease a final try. This time, I cleaned deeper and much more thoroughly – it worked!

We all lit up and had a great holiday.

Hope this helps others enjoy one too.

Cheers,

Jim