Common Symptoms
- Identify causes of hydraulic reservoir overflow during operation.
- Diagnose start solenoid failure and identify warranty eligibility.
- Verify electrical and mechanical causes for loss of bed movement.
- Digital Multimeter — Check battery charge level and verify the quality of the ground connection.
- Wrench Set — Tighten loose hydraulic lines or inlet fittings to prevent reservoir overflow.
- Wire Stripper and Crimper — Repair loose remote wiring or poor connections between the control and the pump.
- Coil Swap Tooling — Interchange coils to determine if a directional movement fault is due to a bad coil.
Reservoir overflowing: usually low battery or bad ground; also loose lines or a loose inlet.
Start solenoid failure: caused by an under-charged battery. Not covered by warranty.
Bed won't go up or down: failed solenoid, poor connection between control and pump, or loose remote wiring.
Pump runs but nothing moves: possibly a stuck valve.
Works one direction only: swap the coils. If the fault follows, the coil is bad.
How It Works
Electrical Impact on Hydraulic Systems
Low battery charge or poor grounding can manifest as physical hydraulic issues, such as reservoir overflow. A start solenoid specifically requires a fully charged battery to function; failure due to under-charging is considered a maintenance issue rather than a defect.
Signal Path Continuity
Bed movement requires a complete signal path from the remote wiring through the controller to the pump solenoids. Failures in any segment of this path, including loose wiring or failed solenoids, will prevent the bed from moving up or down.
Directional Fault Isolation
In systems that work in only one direction, the coils are the primary suspects. By swapping the coils, a technician can isolate the fault; if the symptom moves with the component, the coil is confirmed bad.
Diagnostic Chart
| Symptom | Check | Spec / Expected | Likely cause & fix |
|---|---|---|---|
| Reservoir overflowing | Test battery voltage, inspect ground quality, and check for loose lines or inlets. | Per the applicable manual | Low battery, bad ground, loose lines, or a loose inlet. Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019) |
| Start solenoid failure | Verify battery state of charge. | Per the applicable manual | Under-charged battery; not covered by warranty. Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019) |
| Bed won't go up or down | Inspect solenoid function, remote wiring, and control-to-pump connections. | Per the applicable manual | Failed solenoid, poor connection, or loose remote wiring. Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019) |
| Pump runs but nothing moves | Inspect hydraulic valves for mechanical movement. | Per the applicable manual | Possibly a stuck valve. Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019) |
| Works one direction only | Swap the position of the coils. | Per the applicable manual | The coil is bad if the fault follows the swap. Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019) |
At the Bay: Diagnose the Case
CASE 1 / 5
Reservoir overflowing
- Test
- Compare
- Correct
Select the next check
Basis: KTI DC Power Unit Troubleshooting Guide (Jan 2019). A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.
Common Bay Mistakes
- ✕ Filing a warranty claim for a solenoid failed by an under-charged battery.
- ✕ Replacing the pump for an overflow issue before checking the ground.
- ✕ Assuming a bad pump when the motor runs but a valve is merely stuck.
- ✕ Replacing a remote before checking for loose internal wiring.
- ✕ Replacing both coils when only one direction is failed.
Quick Check
Practice only — not scored.
Hands-on: Shop Test Equipment
Hydraulic Pressure & Relief Gauge
0–5,000 psi gauge on the pump pressure port, DC clamp meter, battery voltmeter
🛠 Equip your bay for this test →Symptom: Routine check before a customer pickup.
Spec limits used
- 3,200 psi — Primary relief (factory preset) (KTI Hydraulics Troubleshooting Manual 2019)
- 1,500 psi — Secondary relief, circuit 111 (KTI Hydraulics Troubleshooting Manual 2019)
- below 9 V — Low-voltage alarm (KTI remote)
- illustrative only — Motor current & voltage drop (General shop practice)
Simulated readings for practice. Always follow the manufacturer's procedure and values on a real trailer.
Source: KTI DC Power Unit Troubleshooting Guide (Jan 2019) — 1