EZ way to check lights

[Borrego Dave]

Got tired of hooking/unhooking the trailer while doing some light mods. I had the extra 7 pin, only wired it for the tail, brakes and running lights. It's not a big deal but it sure is easier than hooking up.

[Dudley]

one more tool for the kit, great idea.

[Larry C Hanson]

Hi,

I use the big battery on the tongue of the
trailer to test all the lights sometimes. 12 VDC
is available on the plug and the lights can be
tested with one test lead. Also, each time I
hook up to pull the rig I turn on the running
lights to test them and then turn on the
emergency flashers to test the brake lights/
turn indicators. On the Trillium that covers all
lights.

Larry H

[Steve L.]

One of my over-winter projects some years back was to take a Radio Shack project box and embed a 7 blade receptacle, some toggle switches, LED's, a 12v accessory socket and a flasher module to make a box that I could plug the trailer into and either test the lights/brakes, power a 12v accessory or flash the trailer clearance lights in the rare occurrence I might have to leave the trailer at the side of the road. (Technically, I'm not supposed to tow a trailer if I've had to install the minispare tire.) I even put a 10a breaker in there. All of it powered by the trailer's on-board battery. I've posted pictures of it here in the past so won't again.


I did another box a few years later and added a digital voltmeter/ammeter function just to show how little charging goes on from the tow vehicle. Both boxes are along the same principle as what Dave and Larry have done if a little more complicated. Well, I was looking for a project after all

[minke]

That is how I charge the brake battery on my boat trailer.

[Keaner]

Originally Posted by Steve L.

One of my over-winter projects some years back was to take a Radio Shack project box and embed a 7 blade receptacle, some toggle switches, LED's, a 12v accessory socket and a flasher module to make a box that I could plug the trailer into and either test the lights/brakes, power a 12v accessory or flash the trailer clearance lights in the rare occurrence I might have to leave the trailer at the side of the road. (Technically, I'm not supposed to tow a trailer if I've had to install the minispare tire.) I even put a 10a breaker in there. All of it powered by the trailer's on-board battery. I've posted pictures of it here in the past so won't again.


I did another box a few years later and added a digital voltmeter/ammeter function just to show how little charging goes on from the tow vehicle. Both boxes are along the same principle as what Dave and Larry have done if a little more complicated. Well, I was looking for a project after all

Steve, where do you pull the power for this box?

[HiLo]

I use a mirror

[Raz]

Like Larry, I use a wire with alligator clips and a couple of pieces of metal or PC board on the 7 pin. Works fine as long as you know which slot is the ground. Dave's solution is safer. Raz

[Steve L.]

Originally Posted by Keaner

Steve, where do you pull the power for this box?

As others noted, the "charge" pin (pin 4) on the connector is normally connected to the battery and thus is "hot". I use it and the ground pin to drive the LEDs and the 12v accessory socket.

Connecting an external battery is not necessary if you have an onboard battery and the connector is wired in the "normal" fashion.

Elsewhere on the site are the pin assignments for various connectors including a 7 blade connector. (Document Center, Electrical, etc.)

[gordon2]

All interesting ways to check to see if the lights work on your trailer and that can come in handy sometimes such as trouble shooting some bad wiring on the trailer.

But what you really need to know is, do the trailer's running lights work when hooked up to, and powered by, the tug? So there is no substitute for making a light check part of your routine when getting ready to depart.

[Alf S.]

Originally Posted by Borrego Dave

Got tired of hooking/unhooking the trailer while doing some light mods. I had the extra 7 pin, only wired it for the tail, brakes and running lights. It's not a big deal but it sure is easier than hooking up.

Hi: Borrego Dave... If your trailer is plugged into 110V... just insert a 15A fuse into the pigtail. Make sure it straddles the ridge of the plug. I have a fuse with the prongs slightly bent... just for this purpose. It will light all exterior lights!!!
Alf S. North shore of Lake Erie

[cpaharley2008]

Originally Posted by Alf S.

Hi: Borrego Dave... If your trailer is plugged into 110V... just insert a 15A fuse into the pigtail. Make sure it straddles the ridge of the plug. I have a fuse with the prongs slightly bent... just for this purpose. It will light all exterior lights!!!
Alf S. North shore of Lake Erie

This method will light all the lights while unplugged from 120v also, as long as you have a battery in your unit.

[Darral T.]

Steve.... can you post a link to your box? That's funny because I'm building one myself as we speak. I found a fairly cheap rheostat to add on the braking side. (There's a story/agenda behind that one.) I ordered 100% of the parts off of Amazon so I've got very little in the box. I too got tired of backing in the truck where the trailer is located just to test all my lights as I'm preparing for a trip. This test is to not not only make sure the 7-pin cord is working but test each individual light- including backup, turn/brake, tail/park lights and brakes. I'd much rather do it a week or so earlier than to be hooked up in the drive about to pull out and realize I have a shot bulb or bulbs!

And yes to who ever posted- I STILL have on my checklist before leaving the driveway to make sure I do a lights/brake check.

Originally Posted by Steve L.

One of my over-winter projects some years back was to take a Radio Shack project box and embed a 7 blade receptacle, some toggle switches, LED's, a 12v accessory socket and a flasher module to make a box that I could plug the trailer into and either test the lights/brakes, power a 12v accessory or flash the trailer clearance lights in the rare occurrence I might have to leave the trailer at the side of the road. (Technically, I'm not supposed to tow a trailer if I've had to install the minispare tire.) I even put a 10a breaker in there. All of it powered by the trailer's on-board battery. I've posted pictures of it here in the past so won't again.


I did another box a few years later and added a digital voltmeter/ammeter function just to show how little charging goes on from the tow vehicle. Both boxes are along the same principle as what Dave and Larry have done if a little more complicated. Well, I was looking for a project after all

[Steve L.]

I can't find a post with a picture of what I refer to as the switch box in a previous post so here it is again.

Since this picture I added a red aircraft-type toggle switch cover over the 2 way (on-off) brake switch to prevent accidentally activating the brakes. Mostly I was goofing around, had the cover, and thought it might increase the nerd coolness(?) The other toggles are on-off-on.

Covered accessory outlet (Marinco) and a 10a pushbutton breaker on the end. The flasher flashes the running lights any time I select "run" (i.e. running lights).

[Darral T.]

Thanks Steve. I've bookmarked this link and will try to post a pic (maybe a vid) of mine once it's finished. It's going to be "over-kill" but I've been studying electronics so I'm throwing a lot into it. But at the same time, I can use it and really want it for the brakes testing...thus the rheostat.

One thing came out of this I didnt think of and that's an emergency flasher switch SHOULD it have to be left on the side of the road! That's one feature I pray I never have to use though.

Originally Posted by Steve L.

I can't find a post with a picture of what I refer to as the switch box in a previous post so here it is again.

Since this picture I added a red aircraft-type toggle switch cover over the 2 way (on-off) brake switch to prevent accidentally activating the brakes. Mostly I was goofing around, had the cover, and thought it might increase the nerd coolness(?) The other toggles are on-off-on.

Covered accessory outlet (Marinco) and a 10a pushbutton breaker on the end. The flasher flashes the running lights any time I select "run" (i.e. running lights).

[Borrego Dave]

Originally Posted by Darral T.

One thing came out of this I didnt think of and that's an emergency flasher switch SHOULD it have to be left on the side of the road! That's one feature I pray I never have to use though.

That's a great idea Darral, don't think I've ever heard of flashers working independently on a TT if disconnected. That may be a good idea to rig up inside the TT as a stand alone function so your box isn't outside for some "nice" person to carry away.

[Darral T.]

Actually, IF one was to be designed exclusively for blinking the lights, I'd just design it so you could lock it onto your RV cord and not have to special rig it inside the trailer which could get touchy. Then I guess you'd have to risk some doe doe cutting your power cord huh?

Originally Posted by Borrego Dave

That's a great idea Darral, don't think I've ever heard of flashers working independently on a TT if disconnected. That may be a good idea to rig up inside the TT as a stand alone function so your box isn't outside for some "nice" person to carry away.

[Steve L.]

At the risk of hijacking the thread, and since Darral's contemplating a electronics project, my second "test" box was to measure voltage and current going to the trailer from the tow. It doesn't activate anything, it only measures/indicates.

There is a shunt in there for measuring amps (calibrated voltage drop acoss the shunt which is proportional to amperage going through the shunt and a (milli)voltmeter chosen to match the shunt such that there is a 1:1 equivalency between millivoltage drop and amps. i.e. the meter is showing millivolts but because of the shunt rating, millivolts also equals the amps. Also a "normal" voltmeter. It was a 50A/50mv shunt.

Some LEDs to show which lights are being activated and another to indicate that the tow is providing a charge voltage to the trailer battery (I have to pay attention to the light emmitting diode's direction so that it is showing volts from the tow, not volts from the trailer, diodes being one-way devices). Basically duplicating the voltage meter. I had fun using different color LEDs this time. And a 9v "transistor radio" battery to run the meters since I didn't want to use the tow voltage to power the meter and effect the meter readings.

The red rocker switch turns off the 9v to save the battery.

Lastly I made a 4' electrical extension so that the box can be put in line with the trailer.

In the photo, the tow is running at a fairly fast idle (not far below the RPM the tow runs at cruising speed) and the fridge is on DC (10amp draw). So the Ford Flex is returning 4.2 amps at 13.96 volts. I lose ground (almost 6 amps per hour of towing) at the trailer battery when towing with the fridge on DC.

[Raz]

Nice job. Like electronic repair, building electronics projects is dying art. Raz

[Darral T.]

Nahh..you aint hijacking. Yer a sharp guy even though we dont agree on digital thermostats . Now thanks to YOU, you got me wanting to add an amp meter in the line. Off of Amazon, I ordered a couple blue LED volt meters. They came in yesterday and look really techy. Wow...just a $2-3!

One thing you mention is the extension. Where did you get the wire? I'm wondering if you just used 2 wires to check the amperage or is it a full 7-wire cable? I found this at Etrailer.com and it doesnt seem too expensive. Here's why I need it and that's so I can reach my wheels as I will use my box with the rheostat to test the brakes equality (already been testing this and it works!).

https://www.etrailer.com/Accessories...DW04914-1.html

[QUOTE=Steve L.;580350]At the risk of hijacking the thread, and since Darral's contemplating a electronics project, my second "test" box was to measure voltage and current going to the trailer from the tow. It doesn't activate anything, it only measures/indicates.