Identify Electric/Hydraulic Breakaway Supply Requirements
- Confirm controller compatibility and identify the installed supply components.
- Match battery, supply circuit, and wiring to the applicable installation instructions.
- Follow the specified no-run checks before the documented breakaway test.
- Digital multimeter — Measure supply voltage between the actuator’s black and white wires under the specified conditions.
- Tape measure — Check actuator distance from the tow vehicle against the installation’s wire-selection guidance.
- Inspection light — Inspect battery labels, wire markings, connectors, and ground connections.
- Insulated hand tools — Access connections and service terminals with electrical power isolated as directed by the applicable instructions.
- Wheel chocks — Secure the trailer against unintended movement before inspection or testing.
An electric/hydraulic actuator supplies pressurized brake fluid in response to the tow vehicle’s braking command. The in-cab controller must be compatible with the actuator; compatibility should not be assumed merely because a controller is installed.
The illustrated arrangement includes a charger, battery, breakaway switch, ground connections, and a hydraulic outlet. Dexter’s schematic specifies a minimum 9 amp-hour battery and a 12-volt, 40-amp tow-vehicle supply circuit; values vary by maker. The schematic permits either an onboard battery or a breakaway battery.
Wire requirements depend on the actuator’s distance from the tow vehicle. Dexter recommends 12-gauge black and white supply wires for distances less than 10 feet and 10-gauge for distances greater than 10 feet, with the other wires at least 16 gauge; values vary by maker.
When the actuator will not run with ignition on and the brake pedal depressed, first compare the installation with the schematic. Dexter specifies 12–13 volts between the actuator’s black and white wires with ignition on and brakes not applied; values vary by maker. The guide then addresses the ground connection and directs the technician to the breakaway test.
How It Works
Command compatibility and hydraulic output
An electric/hydraulic actuator converts the tow vehicle’s braking command into pressurized brake fluid. The in-cab controller must be compatible with the installed actuator; the presence of a controller does not establish compatibility.
Supply capacity and circuit integrity
The illustrated Dexter arrangement includes a charger, battery, breakaway switch, grounds, and hydraulic outlet, and permits either an onboard battery or a breakaway battery. Its requirements include a minimum battery capacity of 9 Ah and a tow-vehicle supply circuit of 12 V, 40 A; these are application-specific requirements. Battery capacity supports operation, while resistance in supply or ground connections can reduce voltage available to the actuator under load.
Distance-based wiring and diagnostic sequence
Dexter recommends black and white supply wires of 12 gauge for distances less than 10 feet and 10 gauge for distances greater than 10 feet, with other wires at least 16 gauge; longer conductors increase resistance and can increase voltage drop. The guidance does not explicitly assign a size at exactly 10 feet, so consult the applicable installation instructions rather than guessing. For a no-run complaint, compare the installation with the schematic, perform the specified supply-voltage check, address the ground connection, and then proceed to the documented breakaway test.
Step-by-Step Procedure
0/7 doneDexter illustrated E/H installation; values vary by maker
| Minimum battery capacity | 9 Ah |
| Tow-vehicle supply circuit | 12 V, 40 A |
| Black-to-white supply check, ignition on and brakes not applied | 12–13 V |
| Black and white supply wires, actuator less than 10 feet away | 12 gauge recommended |
| Black and white supply wires, actuator more than 10 feet away | 10 gauge recommended |
| Other wires | 16 gauge minimum |
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Actuator does not run with ignition on and the brake pedal depressed. | Compare the installation with the applicable schematic and confirm controller compatibility. Then measure between the actuator’s black and white wires with ignition on and brakes not applied; address the ground connection before proceeding to the documented breakaway test. | Dexter supply check: 12–13 V with ignition on and brakes not applied; values vary by maker. | Possible controller incompatibility, incorrect wiring, supply fault, or ground fault; do not condemn the actuator from the symptom alone. Basis: LDServiceOnline |
| Battery capacity or tow-vehicle supply suitability is uncertain. | Identify the battery and charger, read the battery capacity label, and compare the tow-vehicle supply circuit with the applicable installation instructions. | Illustrated Dexter requirements: minimum battery capacity 9 Ah; tow-vehicle supply circuit 12 V, 40 A. Either an onboard battery or a breakaway battery is permitted. | Installed components may not meet the application-specific supply requirements. Basis: LDServiceOnline |
| Supply-wire size cannot be confirmed or appears unsuitable for the installation distance. | Inspect conductor markings and establish the actuator’s distance from the tow vehicle. Consult the applicable instructions if the distance falls at the unassigned boundary. | Black and white wires: 12 gauge recommended below 10 feet; 10 gauge recommended above 10 feet. Other wires: 16 gauge minimum. Exactly 10 feet is not explicitly assigned. | Wire selection may not match the illustrated distance guidance, or the boundary may have been treated as specified when it is not. Basis: LDServiceOnline |
| Operation is intermittent or connections show heat damage. | Isolate power as directed before inspecting terminals for looseness, corrosion, damaged strands, and poor ground contact. Use the applicable procedure for any powered voltage-drop testing. | Use the installed equipment’s service criteria; no connection voltage-drop limit is supplied in this lesson. | Connection resistance can create local heating and reduce available actuator voltage under load. Basis: General shop practice |
At the Bay: Diagnose the Case
CASE 1 / 4
Actuator does not run with ignition on and the brake pedal depressed.
- Test
- Compare
- Correct
Select the next check
Basis: LDServiceOnline. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Treating the illustrated Dexter requirements as universal electric-brake specifications.
- ✕ Assuming an installed controller is compatible with the actuator.
- ✕ Guessing a supply-wire size at exactly 10 feet.
- ✕ Using a brake-applied reading for the specified brakes-released supply check.
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 #9101 Light Ranger MUTT Trailer Tester
Battery-powered tester with a 7-way flat socket and rotary knob — powers one trailer circuit at a time, up to 10 A
🛠 Equip your bay for this test →Symptom: Pre-delivery inspection on a new utility trailer.
Spec limits used
- 10 A @ 12 V DC — Max output per circuit (IPA #9101/#9102 manual, p.5)
- 30 s — Thermal breaker cooldown (IPA #9101/#9102 manual, p.5)
- 11.5 V tester battery — Never operate below (IPA #9101/#9102 manual, p.6)
- 12.2 V — Verify battery charged to at least (IPA #9101/#9102 manual, p.10)
- battery on the trailer detected — Power LED on with knob OFF (IPA #9101/#9102 manual, p.6)
- 3.0 A each — Brake magnet current (warm) (Dexter magnet data (simulator basis))
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: LDServiceOnline — 29-30