LESSON 2 OF 10

Surge Actuator: Fill & Bleed

YOU WILL BE ABLE TO

Perform a complete system fill and bleed on a Dexter surge actuator.
Execute the emergency lever pumping sequence to remove air from brake lines.
Maintain appropriate fluid levels and safety precautions during the bleeding process.

TOOLS AT THE BAY

Brake fluid (DOT 3 or DOT 4) — Fill the master cylinder reservoir to provide the hydraulic medium for the braking system.
Bleeder hose — Direct expelled fluid and air bubbles from the brake bleeder valve into a collection container.
Clear container — Submerge the bleeder hose in fluid to observe air bubbles and prevent air from being pulled back into the system.
Protective gloves and eye protection — Prevent brake fluid from damaging skin, infecting cuts, or contacting eyes.

Brake fluid damages paint and can infect cuts — wear gloves and eye protection.

How It Works

Master Cylinder Maintenance

The reservoir must remain above half full during the bleeding process. Checking the fluid every 4–5 strokes prevents air from being drawn back into the system from the master cylinder side.

Air Displacement Mechanics

Air is purged by pumping the emergency lever with short strokes while the bleeder valve is open. Closing the bleeder valve before releasing the lever ensures a one-way flow of fluid and air out of the system.

Sequential Bleeding Order

Effective bleeding begins at the brake farthest from the actuator. This ensures the longest line runs are cleared of air before moving to the closer wheel positions.

Step-by-Step Procedure

0/7 done

1.Fill the master cylinder with DOT 3 or DOT 4 brake fluid.
2.Remove the lever guide and safety stop plate.
3.Attach a bleeder hose to the brake farthest from the actuator, submerged in a clear container of fluid.
4.Open the bleeder and pump with short strokes on the emergency lever; close the bleeder before releasing.
5.Repeat until no bubbles appear, then move to the next wheel.
6.Check fluid every 4–5 strokes and keep it above half full.
7.Refill the master cylinder and secure the reservoir cap.

Diagnostic Chart

Symptom	Check	Spec / Expected	Likely cause & fix
Air bubbles visible in the clear container during pumping.	Continue pumping the emergency lever with short strokes and closing the bleeder before release.	Repeat until no bubbles appear.	Air is trapped in the brake lines or master cylinder. Basis: Dexter Surge Actuator Owner's Manual OM-A-160
Fluid level dropping rapidly in the reservoir.	Monitor fluid level every 4–5 strokes of the lever.	Keep it above half full.	Normal displacement of fluid into the brake lines during the bleeding process. Basis: Dexter Surge Actuator Owner's Manual OM-A-160
Brake fluid contact with painted surfaces or skin.	Immediate cleanup and use of personal protective equipment.	Per the applicable manual	Fluid spills or failure to wear gloves and eye protection. Basis: Dexter Surge Actuator Owner's Manual OM-A-160

At the Bay: Diagnose the Case

CASE 1 / 3

Air bubbles visible in the clear container during pumping.

Test
Compare
Correct

Select the next check

Basis: Dexter Surge Actuator Owner's Manual OM-A-160. A likely cause is a hypothesis; confirm it with the applicable service procedure before repair.

Common Bay Mistakes

✕ Releasing the emergency lever before closing the bleeder valve.
✕ Allowing the master cylinder fluid level to drop below half full.
✕ Starting the bleeding process at the wheel closest to the actuator.
✕ Failing to remove the lever guide and safety stop plate before pumping.
✕ Mixing incompatible fluids or using fluid other than DOT 3 or DOT 4.
✕ Operating without eye protection despite fluid's ability to infect cuts and damage paint.

Quick Check

Practice only — not scored.

How often should you check the master cylinder fluid level during the bleeding process?

Where should the bleeding process begin?

What action must be taken before releasing the emergency lever during a pump stroke?

Plan the Service Sequence

Surge Actuator: Fill & Bleed

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.

Basis: Dexter Surge Actuator Owner's Manual OM-A-160

Hands-on: Test Bench Practice

VIRTUAL TEST BENCH · SIMULATED READINGS

Symptom: Healthy trailer. Learn what good readings look like.

TrueRMS DMMCAT III 600V

AUTODC

----V

Place both probes

Function dial

10A

COM

VΩ→|

Tap a point to place the red probe.

Controller gain100%

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: 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: Dexter Surge Actuator Owner's Manual OM-A-160 — Bleeding

Next: Surge Hookup & Breakaway →