Trailer Light Tester, home brew

malykaii · Jul 29, 2016

Ign said:
I think it's cool and have been meaning to build a 7 pin tester forever. I wonder if I could power it w a holster from M12 heated gear? Don't see why not.

We have makita 18v batteries at work.

Think I can wire one in? I have a broken flash light so I can make it a clip on ordeal. Getting excited.

Outlander · Jul 29, 2016

I liked the plastic ammo can idea. Simple to work with, you can store plugs/leads inside and it is weatherproof

atomicpunk · Jul 29, 2016

OP, I made something similar years ago that I can hook to any 12v battery laying around the shop with a charge. Also have a flasher and I can connect/disconnect the individual turn signal and brake light wires to check using the flasher. Only problem is the new LED taillights don't draw enough for the flasher to work.
And for the peeps saying hook a truck up not all shop bays have enough room for a truck and trailer, who wants the bay door wide open in the winter with a truck hooked up when I can use my home made tester and shop air.
I was also driving tractor trailers for years in the yard and on job sites before I got my CDL - union co. too.

Outlawmws · Jul 29, 2016

Outlander said:
Yes it does, they all have had flat connectors and I am on my 5th trailer of some nature or another. Pain to keep clean, especially with our winters. I am constantly spraying them with contact cleaner and re-applying di-electric grease.

At the office I would tell my team we have an 'opportunity to excel' You are in your continuous improvement cycle!

Outlander, get yourself a couple of extra flat connectors (you can get a 6" extension cheap) and cut the wires off, then use it as a "dead" plug (with the dielectric grease) when you are not towing. Heck use one on both trailer and vehicle.

Outlawmws · Jul 29, 2016

malykaii said:
So I'll be covering for the tractor and trailer guy for a few weeks and lack a Class A license. Made this to get by.

It hooks up to the shop car's battery and sends power to all lights. 25amp inline fuse. Flasher makes both the brake and turns flash.

Any concerns or improvements to my new toy? Co worker thinks it's a hack job.

Tell the Co-worker to take a flying leap... well done job! I like it! :beer:

You can get a battery out of a dead UPS (or two if you are on 24V) and use that as the power source.

To the guys derailing the thread; just stop. All that has nothing to do with what he's doing, which is making a useful tool...

Outlander · Jul 29, 2016

Outlawmws said:
Outlander, get yourself a couple of extra flat connectors (you can get a 6" extension cheap) and cut the wires off, then use it as a "dead" plug (with the dielectric grease) when you are not towing. Heck use one on both trailer and vehicle.

Good idea - will grab one at the electronics surplus shop next time I am there. Truck does not need it, the connector is built into the bumper with a cover.

HoosierMark · Jul 30, 2016

I built one using a plastic shoe box. I used the lid as my base and mounted a switch and a light to show I had power in general. Then I wired a switch for (each) L/R/S and tail lights. I just flip which ever switch I want. Wires all store in the box when not in use (power, trailer connection, tester light for sockets. Power is from a 4 ft long old cigarette lighter cord with clips. Cost me almost nothing. Works great. Probably not for every day use but for every 3-6 months. It is super. I can flip the lid over to see if any wires are lose etc. I thought about a battery but figured it would drain out for the limited times I would use it.

Ign · Jul 30, 2016

malykaii said:
We have makita 18v batteries at work.

Think I can wire one in? I have a broken flash light so I can make it a clip on ordeal. Getting excited.

I don't think most automotive bulbs would care about 18-20V, but honestly don't know. Also not sure how boards in LED assy's would take it. Anyone?

Outlander · Jul 30, 2016

HoosierMark said:
I built one using a plastic shoe box. I used the lid as my base and mounted a switch and a light to show I had power in general. Then I wired a switch for (each) L/R/S and tail lights. I just flip which ever switch I want. Wires all store in the box when not in use (power, trailer connection, tester light for sockets. Power is from a 4 ft long old cigarette lighter cord with clips. Cost me almost nothing. Works great. Probably not for every day use but for every 3-6 months. It is super. I can flip the lid over to see if any wires are lose etc. I thought about a battery but figured it would drain out for the limited times I would use it.

Hmm.... for power (besides a battery) you could install a plug/receptacle on the box then have both a 12v wall wart from the electronics surplus store (couple of bucks) or a cigarette plug cord. This what I have for one of my work lights. Best of both worlds.

Like you, I probably have everything except the box. A small project box will do the trick. I even have a flasher module from an old Ford Ranger!

Spencer Was Here · Jul 30, 2016

I made two light testers some years ago.

The one to plug into the vehicle I made with long enough wiring that I could sit in the drivers seat of my truck and place it on my lap while I activated the turn signals, reverse, tail, and brake lights.

The second tester I made is to plug into the trailer. I made this one with a 12-volt cigarette lighter adapter that I plug into my portable jump start box to use as a power source. This unit has separate switches that I can independently toggle on or off to active the left or right turn signals, tail lights, reverse lights, brake lights, and the 12-volt circuit.

I know I posted about these two testers years ago when I made them, but I don't remember which forum I posted them on and I couldn't find the original picture on my computer, so I just ran out and snapped a few photos.

You'll be able to tell I have been fortunate enough to not have to use these in a while, as they are filthy from hanging on my barn wall, but I thought these may give some of you ideas for making your own.

Spencer Was Here · Jul 30, 2016

Spencer Was Here · Jul 30, 2016

Spencer Was Here · Jul 30, 2016

Spencer Was Here · Jul 30, 2016

Spencer Was Here · Jul 30, 2016

Spencer Was Here · Jul 30, 2016

Outlawmws · Jul 30, 2016

Ign said:
I don't think most automotive bulbs would care about 18-20V, but honestly don't know. Also not sure how boards in LED assy's would take it. Anyone?

In 12V systems I think you would be losing bulbs on both side of that equation.

The LED's it would be dependent on if it were using a dropping resistor, or a regulator. If the designers know its made for 12V, then a dropping resistor is the simplest cheapest solution.

for 24V system the lights would be dim,

Outlander · Jul 30, 2016

Spencer Was Here said:
I made two light testers some years ago..

Thanks for the pictures!

malykaii · Aug 2, 2016

So I had the pleasure of using my toy this week. I agree, not a heavy duty diagnostic tool... Its more suited for pre-trips and burnt/broken bulbs (aka 95% of trailer work).

Made some wiring improvements. I have the brake lights hooked to the flasher now. Also spliced in a bulb to add resistance for LED trailers.

Found an old distrubutor cap and got it all to fit inside. No longer a pocket item, but less fragile.

Outlander · Aug 2, 2016

This could be my favorite thread of the week

It does look kind of neat tucked into the distributor cap!

pscrow86 · Aug 2, 2016

I'll try and get a picture of our shop tester but it does have a flasher as well as a toggle switch to test electric brakes I believe. We mainly use the the small 6 pin round plugs on our trailers and compressors.

maxpower_hd · Aug 3, 2016

I was never able to see the original photo for some reason. But here is one of the one at our shop. One of the other guys actually built it. It will light LED's but won't always make them bling. So if you set up a mirror and blink it manually it will work for those too. Or if there is an incandescent one in the circuit it will usually work too.

justme- · Aug 6, 2016

We have a commercial made tester for our trailers (not class a) , but I hardly use it opting for my made rig. I have a 18ah sla battery I wired a 4 pin flat truck side on with inline fuse and spade connection on the feed so I can power each circuit as needed.

Commercial testers, especially that ammo box size don't have large enough batteries to run lights for long. Thats why I don't usually use our shop one...doesn't have enough battery to run a box trailer with all the marker lights.
While it does have a flasher And automatic circuit switching if it worked more than 2 minutes on a charge it'd be useful.

We just yesterday put my test battery into a shop booster pack that needed a new battery and the trailer pigtail was cut through the case. Easier to carry. I made a reverse adapter to go from 4 pin to 7 pin and can hook brake power in also.

Nice job on yours.

MW. · Aug 6, 2016

Search for a "flasher for led turn signals". You could use an electronic flasher on the led lights if you want to get rid of the extra bulb or need more room for something else.
Nice job.

bonneyman · Aug 6, 2016

Love all the devices you guys have made.

Macgyver would be proud! :thumbup:

nickelmore · Aug 6, 2016

Looks great to me. The question I have is.....that is the same connector that is on the front of all trailers. Are you using a known good 7 way cord to plug in between your test connector and the trailer?

I made one years ago when I had to do road service that had both connectors on it. Chicago winter in the middle of the night isolated a bad cord or tractor wiring from the trailer right away.

maxpower_hd · Aug 6, 2016

We use a known good cord and all ours are the same.

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