Does the testerwork wothout the trailer being attached?

Yes. You can utilize the tester to test the tow vehicle side of connection without the trailer attached to it. Hope this helps.

Does it work on bulbs that aren't LED

Yes - This is testing your wiring, not your bulbs. The only reason the description mentions LEDs is because the indicator lights on the tester are long lasting LED.

tried this today, when I turn on the left or right directional all the lights light up on the tester? is it supposed to be all lights?

Only one LED will light showing left or right or tail lights. Sounds like you have a wiring problem in the vehicle's wiring to the connector. I would check the ground connection for good continuity to the auto frame. An 'open' ground would allow all lights to light as you describe. You could verify that the tester is ok by trying it on another vehicle, too.

Why are all three lights on when connecting the trailer and car? Lights arent working on the trailer and the tester works when only connected to the c

it shows there is electric to that poin not thoughtto th blubs on thr trailer

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Fully operational. Shipping worldwide, on schedule.Duty & taxes paid at delivery

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True MODS 4-Way Flat Trailer Light Tester 4-Pin Wiring Circuit Test

True MODS 4-Way Flat Trailer Light Tester 4-Pin Wiring Circuit Test

Product ID: 77742154

Details

Brand
ONLINE LED
Color
Black
Item dimensions L x W x H
6.5 x 3.74 x
Power Source
Corded
Style
Flat

⚡Nickel-plated copper terminals for superior conductivity

🔌4-pin flat trailer wiring compatibility

🛠️Plug-n-play no-tools-needed design

1828 kr

Duties & taxes included

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Sold byAmazon IcelandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

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Description

🚛 Light up your trailer troubleshooting game—fast, foolproof, and fail-safe!

COMPACT READY TO GO - Slim two-sided design fits glove box or toolbox for on-the-go troubleshooting.
ZERO TOOLS ZERO HASSLE - Plug-n-play simplicity means anyone can test trailer lights in seconds.
BUILT TO BRAVE THE ELEMENTS - Weatherproof, corrosion-resistant, and impact tough for years of reliable use.
SPLIT CONQUER WIRING ISSUES - Isolate faults quickly by testing tow vehicle or trailer side separately.
INSTANT TRAILER LIGHT DIAGNOSTICS - Plug inline and get immediate LED feedback—no guesswork, no delays.

The True Mods 4-Way Flat Trailer Wiring Tester is a compact, durable diagnostic tool featuring nickel-plated copper terminals and a plug-n-play design. It enables quick, tool-free testing of 4-pin trailer light circuits by isolating wiring faults between tow vehicle and trailer. Weather and impact resistant, this tester delivers reliable, on-the-spot LED feedback to save time and prevent electrical wear.

Specifications

ASIN	B07G8Q5LMS
Best Sellers Rank	#26,318 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #40 in Circuit Testers
Brand Name	ONLINE LED STORE
Color	Black
Compatible Devices	Vehicles with 4-pin trailer connector and trailers with 4-pin connector
Customer Reviews	4.6 4.6 out of 5 stars (2,632)
Item Dimensions	6.5 x 3.74 x 0.7 inches
Item Highlight	Nickel-Plated Copper Terminals, Male & Female, Continuity Test
Manufacturer	ONLINE LED STORE
Measurement Type	Electrical Measurement Device
Model	8542039913
Number of Items	1
Part Number	ACCEPSTST0031
Power Source	Corded Electric
Style Name	Flat
UPC	816165026065
Unit Count	1 Count
Upper Temperature Rating	60 °C

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Trustpilot

TrustScore 4.5 | 7,300+ reviews

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The product exactly matches the description. Very satisfied with my purchase.

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The delivery time was excellent, and the packaging was secure.

2 months ago

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1828 kr

Duties & taxes included

In stock

Sold byAmazon IcelandDelivered byDesertcartCustomer service byDesertcartReturns14 days · 30 with PRO

Buyer Protection · Full refund if your order doesn't arrive as described.

Desertcart purchases this item on your behalf and handles shipping, customs, and support to Iceland.

Secure transaction

Trustpilot

TrustScore 4.5 | 7,300+ reviews

Anita G.

Good experience, but the tracking updates could be better.

2 months ago

Farhan Q.

The delivery time was excellent, and the packaging was secure.

2 months ago

View all Trustpilot reviews