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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🚛 Light up your towing game with confidence!

ZERO HASSLE SETUP - No tools or technical skills required—just plug in and test.
DUAL SIDED TESTING POWER - Test both tow vehicle and trailer wiring separately to isolate issues fast.
COMPACT PORTABLE DESIGN - Fits easily in your glove box or toolbox for on-the-go peace of mind.
RUGGED WEATHERPROOF BUILD - Nickel-plated copper terminals and impact-resistant housing for long-lasting durability.
INSTANT TRAILER LIGHT DIAGNOSTICS - Plug inline and instantly identify wiring faults with clear LED signals.

The ONLINE LED STORE 4-Way Flat Trailer Wiring Tester is a compact, durable diagnostic tool designed for quick and easy testing of 4-pin trailer light circuits. Featuring nickel-plated copper terminals and LED indicators, it allows users to isolate wiring issues between tow vehicle and trailer without any tools. Its weather-resistant construction and plug-n-play design make it an essential accessory for professional-grade trailer maintenance and hassle-free towing.

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Manufacturer	ONLINE LED STORE
Brand	ONLINE LED STORE
Product Dimensions	16.51 x 9.5 x 1.78 cm; 32 g
Item model number	8542039913
Manufacturer Part Number	ACCEPSTST0031
Item Weight	32 g

ONLINE LED STORE 4-Way Flat Trailer Wiring Tester [Nickel-Plated Copper Terminals] [Male & Female] [Continuity Test] 4-Pin Trailer Light Wire Circuit Tester

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