Powering the LT35 Light Tester
1. Powering the LT35 using trailer’s on-board battery: The LT35 can
be powered by your trailer’s on-board battery (if equipped) through the 7-
way connector. If your trailer is capable of powering the tester, the LT35’s
Power Status LED will illuminate when your trailer’s 7-way connector is
plugged into the tester. Note: Some trailers have a diode in their circuitry
that prevents them from powering this tester.
2. Powering the LT35 using its cigarette lighter plug: The LT35 can
be powered by any 12v negative ground power source, such as a portable
power pack, jump box, or auto battery capable of supplying a minimum of
10 amps. The LT35’s Power Status LED will illuminate when the cigarette
lighter plug is attached to a 12v power source. Note: When using a trailer
Connector Adapter to connect the LT35 to a trailer that has a 4, 5, or 6-
way connector, power your tester using this method.
Using the LT35 Light Tester
1. Ensure the tester’s Power Status LED illuminates: Fully plug-in
the trailer’s connector into the LT35 tester, check that the tester’s
Power Status LED illuminates. If it doesn’t, confirm the trailer’s battery is
charged or plug tester’s cigarette light plug into a suitable 12v power
source.
2. Tail & Marker Light Test: Rotate the control knob to position 1, check
to ensure the trailer’s tail and marker lights are ON.
3. Brake Light Test: Rotate the control knob to position 2, check to en-
sure the trailer’s brake lights are ON.
4. Turn Signal Light Test: Rotate the control knob to position 3 or 4,
check to ensure the trailer’s left or right turn signal lights are flashing ON.
Trouble-Shooting
Power Status LED does not illuminate when powering the LT35 with
the trailer’s battery.
Trailer has poor connection with LT35 tester. Solution: Check & clean 7-way
connector, and ensure it is fully plugged-in.
Circuit breaker may be tripped. Solution: Reset the circuit breaker by pushing the
button down until it stays in the lowered position. If the circuit breaker continues
to trip, there’s likely a short-circuit in your trailer’s wiring.
Trailer’s battery maybe discharged or connected improperly. Solution: Charge
trailer’s on-board battery and check for proper polarity when connecting battery.
Trailer may not be capable of providing power to LT35, due to diode in trailer’s
circuitry. Solution: Power LT35 through cigarette light plug using an auxiliary
power source.
Power Status LED does not illuminate when powering the LT35
through its cigarette lighter plug.
Low voltage from 12v power source or reverse polarity. Solution: Ensure power
source is providing a minimum of 12v and check for proper polarity.
Circuit breaker may be tripped. Solution: Reset the circuit breaker by pushing the
button down until it stays in the lowered position. If the circuit breaker continues
to trip, there’s likely a short-circuit in your trailer’s wiring.
The cigarette lighter plug may have a blown fuse. Solution: Unscrew the tip of
the cigarette lighter plug to inspect the 10A fuse, replace fuse if blown.
Power Status LED is On, but trailer lights do not turn On.
Low voltage from 12v power source. Solution: Charge power source’s battery.
Check trailer for faulty lights, wiring, grounds, battery polarity, etc.
Circuit Breaker keeps tripping.
The circuit under test likely has a short circuit, which is typically a 12v wire that is
shorting to ground. Solution: Check and repair if needed affected circuits wire for
cuts, damage or pinching.
