Check Breakaway Readiness and Trailer Lights
- Verify breakaway battery, switch, and actuating-chain readiness.
- Inspect connector security, lights, and brake operation before travel.
- Apply the correct battery storage and charging instructions.
- Digital multimeter — Check battery voltage and trace electrical faults using the applicable equipment instructions; do not treat voltage alone as proof of battery capacity.
- Compatible battery charger — Charge the breakaway battery according to its chemistry and the applicable manufacturer instructions.
- Flashlight — Inspect the battery enclosure, switch, actuating chain, connector, and exposed wiring.
- Basic hand tools — Access battery terminals and remove the battery for storage, following applicable disconnect and installation instructions.
- Wheel chocks — Secure the trailer against unintended movement during stationary inspection and testing.
The breakaway battery supplies power to actuate the trailer brakes if the trailer separates, and the breakaway switch connects that battery power to the brakes. This emergency function makes battery and switch condition important parts of electrical readiness.
Before use, check battery charge and breakaway-switch operation. The pretrip checklist also calls for secure engagement of the breakaway-switch actuating chain and a fully charged breakaway battery.
Confirm that the electrical connection is secure and check all trailer lights. Brake engagement and synchronization are also included in the pretrip inspection, rather than being replaced by a lighting check.
For extended storage, remove the emergency breakaway battery and keep it indoors out of the weather. Lippert specifies charging it at least every 90 days during storage; this interval is source-specific and values vary by maker.
How It Works
Breakaway readiness is a complete electrical path
The breakaway battery supplies emergency brake power, while the breakaway switch connects that power to the brakes if the trailer separates. A weak battery, damaged connection, or faulty switch can interrupt this function, so battery charge and switch operation must both be checked. Secure engagement of the actuating chain is also essential because the switch must be mechanically actuated when needed.
Working lights do not prove working brakes
A secure electrical connector and functioning trailer lights are required pretrip checks, but they do not establish breakaway readiness or brake performance. Separate circuits and components can fail independently, so brake engagement and synchronization require their own checks. Verify scheduled maintenance is current and allow time for repairs before travel.
Storage care preserves emergency readiness
For extended storage, remove the emergency breakaway battery and keep it indoors out of the weather. Batteries can lose charge while idle, leaving insufficient energy for emergency brake actuation. Lippert specifies charging at least every 90 days during storage; this interval is source-specific, and the applicable maker's instructions govern other equipment.
Step-by-Step Procedure
0/7 doneLippert breakaway-battery storage interval; values vary by maker
| Recharge during extended storage | At least every 90 days |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Breakaway battery is not fully charged before travel. | Inspect battery condition and connections, then charge and assess the battery according to applicable instructions. | Check that the breakaway battery is fully charged before use. | Possible storage discharge, inadequate charging, poor connections, or battery deterioration. Basis: Lippert-Axle-Manual |
| Brakes do not actuate during the prescribed breakaway test. | Secure the trailer, verify battery readiness and actuating-chain engagement, and test switch operation according to applicable instructions. | Check breakaway-switch operation and confirm that the actuating chain is securely engaged. | Possible inadequate battery power, switch failure, interrupted wiring, or a brake-system fault. Basis: Lippert-Axle-Manual |
| Trailer lights flicker or fail when the connector moves. | Inspect connector retention, terminal condition, cable strain, and ground connections; isolate the fault with the circuit de-energized where appropriate. | Use applicable connector and wiring instructions; no numerical electrical limits are provided here. | Possible loose terminals, corrosion, damaged conductors, or poor grounding. Basis: General shop practice |
| Lights work, but trailer braking is absent or poorly coordinated. | Check brake engagement and synchronization separately from lighting, following the applicable trailer and brake-control instructions. | Check all trailer lights, brake engagement, and synchronization before travel. | Possible brake-control, brake-circuit, or mechanical brake fault despite a functioning lighting circuit. Basis: Lippert-Axle-Manual |
At the Bay: Diagnose the Case
CASE 1 / 4
Breakaway battery is not fully charged before travel.
- Test
- Compare
- Correct
Select the next check
Basis: Lippert-Axle-Manual. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Assuming working lights prove breakaway readiness.
- ✕ Treating battery voltage alone as proof of usable capacity.
- ✕ Improvising a breakaway test instead of following applicable instructions.
- ✕ Applying Lippert's storage charging interval to every battery maker.
Quick Check
Practice only — not scored.
Plan the Service Sequence
Planning practice only. Follow the applicable manufacturer's instructions, employer safety program and qualified supervision on real equipment.
Plan the first action. Compare the service steps with the bay mistakes.
Hands-on: Test Bench Practice
Symptom: Healthy trailer. Learn what good readings look like.
Tap a point to place the red probe.
Good system: ~12.6 V at pins, 3.2 Ω across a 12×2-inch magnet (unplugged), 3.0 A per magnet at 12 V full gain, and at least 10.5 V at the magnet — the chart values from the axle manuals.
Hands-on: Shop Test Equipment
IPA #9107B Electric Brake Force Meter
Plugs into the truck's 7-way socket on a 25 ft cable; simulates a trailer load and shows controller output on 10 blue LEDs
🛠 Equip your bay for this test →Symptom: Customer wants the truck checked before buying a trailer.
Spec limits used
- 1–10, each 1.0–1.5 V — Gain LEDs (IPA #9107B manual, p.5)
- 15 s — Max time holding brake pedal (IPA #9107B manual, p.4)
- set-up step 5 — Connect the 9-pin only after the engine is running (IPA #9107B manual, p.3)
- hold brake pedal during ECU detection — 2016–2017 'Trailer Connected' not shown (IPA #9107B manual, p.3)
- faulty brake control module or relay — ECU light never lights on a vehicle with a controller (IPA #9107B manual, p.5)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Hands-on: Wire-Trace Overlay
Pin 2 · Blue
Electric brakes
- Left and right brake magnets
- Breakaway switch output
Check points
- Two brakes draw about 6.0 A (3.0 A per magnet) at 12 V full gain.
- Unplugged: 3.2 Ω per magnet; at least 10.5 V at each magnet under load.
Common failures
- Open magnet: about half the expected current and a pull to one side.
- Shorted magnet: very low resistance and controller overload.
- Wire chafed where it drops to the axle.
Colors shown are the most common RV harness colors; makers vary — always verify against the trailer's wiring diagram.
Source: Lippert-Axle-Manual — 22, 41-42