Dometic HC4645H User manual

Dometic Hydraulic Steering Systems
Troubleshooting Guide
[REVISION C] Form No. SL61501 | ©2020 Dometic Corporation
WARNING
Cancer and Reproductive Harm
www.P65Warnings.ca.gov
EN
HYDRAULIC STEERING
SYSTEMS

ii EN
All information, illustrations and specifications in this manual are based on
the latest information available at the time of publishing. The illustrations
used in this manual are intended as representative reference views only.
Moreover, because of our continuous product improvement policy, we
may modify information, illustrations and/or specifications to explain and/
or exemplify a product, service or maintenance improvement. We reserve
the right to make any change at any time without notice.
©2020 Dometic
All Rights Reserved. This document, subject matter and all information
herein is the sole, exclusive and confidential property of Dometic and shall
not be disclosed, copied, reproduced or used in whole or in part for any
purpose other than as specifically authorized in writing by Dometic.
is a registered trademark of the American Boat &
Yacht Council (http://www.abycinc.org)
NMEA 2000® is a registered trademark of the National Marine
Electronics Association.
Optimus, Optimus 360, SeaStar, and BayStar are all trademarks of Dometic.
California
Proposition 65 Warning
Battery posts, terminals, and related accessories contain
lead and lead compounds, chemicals known to the state
of California to cause cancer and reproductive harm.
Wash hands aer handling.
This book contains:
• the troubleshooting information for Dometic hydraulic steering systems.
Thank you for choosing Dometic Hydraulic Steering. You have chosen a
state of the art steering system that will provide years of effortless and
trouble free steering performance.
About this Book

iii
EN
Table of contents
1 Important safety information ................................................. 1
1.1 Explanation of symbols ..................................................... 2
1.2 Safety considerations and safe operation ............................ 3
2 How to use this manual.......................................................... 5
3 Common terms and definitions ............................................. 5
4 Manual troubleshooting........................................................ 6
4.1 Loss of fluid/fluid level not visible in helm pump ................... 6
4.2 Helm locks up completely................................................. 7
4.3 Difficulty purging the air from the system............................. 8
4.4 Steering wheel(s) are hard to turn at dock ............................ 9
4.5 Steering wheel(s) are hard to turn while underway
(easy at dock) ................................................................. 10
4.6 Steering wheel(s) freewheel(s) to one/both direction(s) ........ 11
4.7 Steering wheel(s) are bumpy when turning either direction..... 12
4.8 Boat drifts to one side or the other while underway ............. 13
5 Power Assist system troubleshooting .................................. 14
5.1 Steering wheel(s) “lock up” to one or both directions........... 14
5.2 Power Assist motor runs but NO power assist ..................... 15
5.3 Bumpy feeling at steering wheel(s) with power assist
turned ON ..................................................................... 16
6 System checks ...................................................................... 17
6.1 Checking for air in the steering system ............................... 17
6.2 System pressure test........................................................ 18
6.3 Cylinder/helm pump check.............................................. 19
6.4 Helm/cylinder & power assist checks ............................... 20
7 Routine maintenance........................................................... 22
8 Specifications and replacement parts .................................. 24
8.1 BayStar ......................................................................... 24
8.2 SeaStar......................................................................... 25
8.3 Fitting identification........................................................ 26
9 Advisory notice..................................................................... 27
9.1 Power Assist pumps ....................................................... 27
9.2 How to determine if your power assist is affected ............... 27
9.3 How to disable the power assist....................................... 28
9.4 How to obtain a service kit .............................................. 28
10 How to test the SeaStar power assist....................................29
10.1 Test procedure .............................................................. 29

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1
EN
1 Important safety
information
This troubleshooting guide is written using years of experience
troubleshooting the most common problems associated with our steering
systems. Most faults are directly related to installation and operating
manual(s) not being followed or incorrect parts being used.
The purpose of this troubleshooting guide is to systematically work your
way through the system, centering in on the most likely problem.
When you find a fault, it is good practice to determine “how” the fault was
created and “what” can be done to prevent this in the future.
Please carefully read and follow all instructions, guidelines and warnings
included in this product manual in order to ensure that you install, use and
maintain the product properly at all times. By using the product, you
hereby confirm that you have read this disclaimer, all instructions,
guidelines and warnings carefully and that you understand and agree to
abide by the terms and conditions as set forth herein. You agree to use this
product only for the intended purpose and application and in accordance
with the instructions, guidelines and warnings as set forth in this product
manual as well as in accordance with all applicable laws and regulations.
A failure to read and follow the instructions and warnings set forth herein
may result in an injury to yourself and others, damage to your product or
damage to other property in the vicinity. Dometic accepts no liability for
any loss, damage or injury incurred, directly or indirectly, from the
installation, use or maintenance of the product not in compliance with
the instructions and warnings in the product manual.
This troubleshooting guide, including the instructions, guidelines and
warning, and related documentation may be subject to changes and
updates. For up-to-date product information, please visit:
https://documents.dometic.com and https://www.dometic.com

2EN
The symbols below are used throughout this publication to alert you to
potential hazards involved with the operation and installation of this product.
Observe these warnings and notices carefully. The safety alerts alone
cannot eliminate hazards; strict compliance with any special instructions
during installation, operation, and maintenance, along with common sense
operation, are important measures to prevent hazardous situations.
1.1 Explanation of symbols
DANGER!
Safety instruction: Indicates a hazardous situation that, if not avoided,
will result in death or serious injury.
WARNING!
Safety instruction: Indicates a hazardous situation that, if not avoided,
could result in death or serious injury.
CAUTION!
Safety instruction: Indicates a hazardous situation that, if not avoided,
could result in minor or moderate injury.
NOTICE!
Indicates a situation that, if not avoided, can result in property damage.
NOTE
Supplementary information for operating the product.

3
EN
1.2 Safety considerations and
safe operation
Before installation
The safe operation of the steering system is dependent upon proper
installation & maintenance, common sense, safe judgment and the
knowledge/expertise of the operator. Every installer/user should know the
following requirements before installing/using the steering system.
1. Read and understand the installation and operating manual provided
with your motor, steering system, and associated components.
2.
Ensure that all components required to complete the installation are on hand.
3. Dometic components are highly engineered and safety tested to ensure
system integrity; do not substitute any component with non-Dometic
components as this may compromise system performance/reliability.
WARNING!
The safety information provided throughout this publication is intended to
inform you of the dangers that may be present during installation and use.
It is critical that you read and understand all the points noted.
If you have any questions regarding any of these warnings, contact Dometic.
CAUTION!
Helms and cylinders that end with the suffix -3 use ORB fittings only. Do not
use NPT fittings. Irreparable damage will occur.
During installation
1. Install components as directed in all Installation Instructions.
2. Do not modify or substitute any component in any way without written
consent from Dometic.
3. Comply with all system ratings/regulations (boat/engine, U.S.C.G.).
• cylinder must be compatible with engine(s) installed.
• cylinder must be rated for use on the engine(s) installed.
4. Confirm that there is no interference between the steering cylinder(s),
tiebars and the transom, splashwell, outboard engine(s) or jackplate or
any combination of these parts by performing the following steps;
a. With engine fully tilted down, turn steering wheel from hard over to
hard over and confirm that no interference occurs.
• If using a hydraulic jack plate the above must also be performed at
all the positions of the jackplate.
b. Repeat step 4a) with engine(s) tilted up.
c. Perform step 4a) with each engine in down/up positions confirming
that independent trim/tilt can be done without any interference.
5. Confirm that the steering cylinder(s) can be fully stroked in both
directions as well as full tilt and trim without stretching, chafing, rubbing
and/or kinking of the hydraulic hoses.

4EN
6. Outboard Systems: Confirm that extruded nylon tubing has not been
substituted for SeaStar steering hose.
7. Do not use a wire coil type trim switch with a hydraulic steering system
as the wire can wind up tight around the steering wheel shaft and
prevent further steering.
8. Conduct oil level and system check as outlined in the component’s
installation manual.
NOTICE!
Do not operate boat if any component is not in proper working condition.
NOTICE!
Do not operate boat if any component is not in proper working condition.
Prior to every use
1. Check fluid level in highest helm pump. (Refer to installation and
operating manual for correct fluid level setting.)
2. Verify immediate steering response when turning steering wheel(s).
(Ensure engine turns when steering wheel is turned.)
3. Visually inspect all steering hoses and fittings for wear, kinking
and/or leaks.
4. Check for binding, loose, worn or leaking steering components.
During use
1. Rinse off steering system thoroughly using ‘fresh, clean water only’.
• Cleaning fluids containing ammonia, acids or any other corrosive
ingredients must not be used for cleaning any part of the hydraulic
steering system.
After use
1. Rinse off steering system thoroughly using ‘fresh, clean water only’.
• Cleaning fluids containing ammonia, acids or any other corrosive
ingredients must not be used for cleaning any part of the hydraulic
steering system.
Maintenance
1. Maintain steering system at a minimum of twice per year.
2. See maintenance section in the component’s installation manual.

5
EN
2 How to use this manual
3 Common terms and
definitions
Each fault will be labeled as a “Symptom” at the top of the page, followed
by possible “Causes”, and then followed by possible “Solutions”.
• Symptom = Problem reported
• Causes = Most likely cause that can lead to the symptom
• Reasons/Solutions = Cures for the symptoms
In cases where there are multiple “causes” a series of checks and tests will
be required. Go through these checks/tests in the order that they appear.
Doing so will quickly narrow in on specific areas. Skipping steps will only
lead to more time diagnosing the problem.
Helm Pump – Located at all steering locations. The steering wheel is
mounted to the helm pump.
Steering cylinder – Mounted to engine(s), rudder(s) and/or outdrive(s).
Manual System – Consists of helm(s), steering cylinder(s) and hoses only.
Power Assist – Electrically driven power pump plumbed into a manual system.
Balanced System – A steering cylinder that the piston rod goes in and
out of both sides of the barrel.
Unbalanced System – A steering cylinder that the piston rod only goes in
and out of one side of the barrel. NOTE: Cannot be used with a Pro helm.
Autopilot Pump (A/P Pump) – External pump plumbed into the steering
system and used in conjunction with an autopilot controller.

6EN
4 Manual troubleshooting
Causes
A. Leak in steering system.
B. Air remaining in system/system not properly bled originally/fluid level
set too low.
Solutions
4.1 Loss of fluid/fluid level not
visible in helm pump
WARNING!
Repair all leaks prior to use.
A. Check all fitting connections, hoses and steering components for any
signs of a leak. See system pressure test on page 18 to pinpoint
source of leak.
B. Bleed system free of air. Reference “Checking for air in the steering
system” on page 17. Fluid level is to be set be tween 1/4” – 1/2”
below the filler port threads.
Refer to section 4.3 If having difficulty purging.
NOTICE!
When using an unbalanced cylinder the fluid level is to be set and
inspected with the cylinder shaft fully “retracted”. Failure to have cylinder
rod fully retracted will result in fluid leakage at the helm filler port.
Root Causes
• Damage to a cylinder shaft (dings, dents, corrosion and/or scratches)
will lead to the tearing of a seal resulting in a leak. Replace any damaged
shaft and/or end gland.
NOTICE!
Replacement shafts are not available for purchase. Contact Authorized
Service Center for repair, or, replace steering cylinder(s).

7
EN
Causes
A. PRO helm used with “unbalanced” steering cylinder.
B. Mechanical interference.
C. Restriction in hose/helm.
Solutions
A. A SeaStar PRO helm cannot be used with any unbalanced cylinder, this
will result in the steering wheel locking up completely.
B. Mechanical interference (see checks below).
C. Restriction in steering lines or helm (see checks below).
Checks
Mechanical interference:
B-1. Using an assistant, turn steering wheel from hard-over to hard-over.
Visually inspect steering cylinder(s) and engine(s) for any signs of
interference with any other object. Check is to be completed
throughout the trim/tilt positions of the engine(s), including jackplates.
This check should be done while underway as well.
B-2. Tilt Helm Installations
a. Confirm that the steering wheel hub is not interfering with the tilt
cover. Correct as required.
b. Disassemble tilt covers and inspect tilt mechanism for any loose
or separated components. Inspect socket head bolts holding
the coupler together to make sure they are tight and not allowed
to contact any other parts of the steering assembly. Correct
as required.
Hose/Helm Restrictions:
a. Mark and remove hoses from steering cylinder.
b. Place hoses in a catch can.
c. While filling helm with fluid, turn 1 turn to port, then 2 turns
to starboard.
• If the steering wheel cannot be turned in one direction, swap
steering lines at rear of the helm pump and repeat above.
• If the problem moves to the other side, replace that side
steering line.
• If the problem persists, replace helm pump.
4.2 Helm locks up completely
CAUTION!
Any interference must be corrected prior to use.

8EN
Causes
A. Incorrect bleeding procedure being followed.
B. Looping of steering hoses.
C. System plumbed incorrectly.
D. Cylinder prevented from hitting hard-over.
E. Clogged filter(s) in power purge unit (dealer/builder tool).
Solutions
A. Refer to installation and operating manual and/or web site for proper
bleeding procedures. Use only Dometic printed or video instructions.
B. Steering hoses MUST be installed with a gradual rise with no loops.
If installation has several loops, re-route or replace hoses with shorter
lengths. Lay loops flat on deck until purging has been completed.
C. Refer to your Installation Manual to confirm system is plumbed
properly.
D. Steering cylinder MUST hit hard-over.
E. Remove power pump from power purge unit. Clean screen filters
located on pump pick up tubes (inside the reservoir).
Dometic recommends the use of Power Purge service kit part # HP6125 for
this procedure.
Root Causes
A. There are several variations (catamarans) as well as additions (autopilots
and power assist pumps). Each system may have a unique step added
for bleeding the air out of the system
B. Hoses are too long.
C. Plumbing schematics not followed correctly.
D. Mechanical restriction preventing steering cylinder from reaching
hard-over.
E. Contaminated fluid in power purge reservoir. Refer to power purge
flushing details.
4.3 Difficulty purging the air from
the system
NOTICE!
In multiple stations, autopilots and power assist applications there MUST
be a compensating line installed.

9
EN
Causes
A. Mechanical interference.
B. Cylinder Adjusting nut over-tightened.
C. Restriction in steering hoses.
D. Wrong fluid being used to fill system.
E. Cylinder not installed correctly, or, incorrect cylinder used for
the application.
F. Steering wheel is too small for use, ensure engine moves freely.
G. Length of hoses or the use of tubing.
H. The way the system is plumbed.
Solutions
A. Check for mechanical interferences. See section 4.2.
B. Loosen cylinder adjusting nut confirm heavy steering is still present.
CSee section 4.2 (C) “Restriction in hose”.
D. Use of any other fluid may lead to heavier steering.
Use SeaStar steering fluid only.
E. Consult with Installation and Operating Manual confirming that the
cylinder is the correct one for the application and is installed correctly.
F. Disconnect steering cylinder from engine, then, using your hands push
engine back and fourth. You should “easily” be able to swing the
engine throughout its turning arc. If engine is NOT easy to turn
throughout the turning arc, locate the restriction and correct.
G. If using tubing try SeaStar hoses. The length of hoses can result in
harder steering.
H. Check to see if your system is plumbed in series or parallel.
Checks
• Disconnect steering cylinder from engine. If wheel becomes easy to
turn, check the engine for restriction.
4.4 Steering wheel(s) are hard to
turn at dock

10 EN
Causes
A. Torque tab not adjusted properly.
B. Engine not being trimmed properly when underway, or engine
mounted too low.
C. Excessive steering loads from prop(s).
NOTE: the use of chopper and cleaver props are not advised.
D. Steering system is not adequately sized for boat/user performance.
Solutions
A. Check different settings with the torque tab to narrow in on the boat’s
“sweet spot”.
If after trying all possible positions the steering is still heavy one
direction it is recommended that a “Torque Tamer” is installed.
B. Confirm that the engine is being trimmed properly, and that the
cavitation plate is set correctly for the hull.
C. See Solution B.
D. Reduce steering effort by increasing your mechanical advantage (add
more wheel turns) by
• decreasing your helm displacement
• adding additional steering cylinder (if possible)
• installing a SeaStar power assist for fingertip steering
• install larger steering wheel.
4.5 Steering wheel(s) are hard to turn
while underway (easy at dock)
NOTICE!
All outboard engines create propeller torque that want to turn the engine,
making it easy to turn the wheel 1-direction (typically starboard), and hard
to turn the other (typically port). Each engine/boat combination will have
different effort. The following causes and solutions can reduce this effort.

11
EN
Causes
A. Air in the system (most common cause). Refer to the “quick reference
turns” tables on page 17 and page 18 to confirm lock to lock turns.
B. Dirt or debris in helm pump valves.
C. Internal bypass in steering cylinder and/or autopilot pump.
Solutions
A. Confirm that system is full of fluid and bled free of air. Refer to
installation and operating manual for filling and purging procedures.
B. Check fluid condition for signs of milky, dirty or contaminated fluid.
Flush system as noted on page 21.
C. Conduct the cylinder/helm pump test on page 20.
4.6 Steering wheel(s) freewheel(s) to
one/both direction(s)
NOTICE!
On multiple helm applications, there is a possibility to enter a slow
freewheel situation if 1–helm is turned 1–direction and then the opposite
helm is slowly turned the opposite direction. This is normal and can be
stopped by performing a quick, partial turn of the wheel to fully close a
hydraulic valve.
CAUTION!
A system that is not responding must be diagnosed and corrected
prior to use.
WARNING!
Dometic does not recommend the disassembly of any helm pump.
Contact an Authorized Service Center, or, replace helm pump.

12 EN
Causes
A. Air in the system (most common cause).
B. Incorrect steering cylinder installed.
C. Faulty tilt mechanism.
D. Faulty check valves in helm pump.
E. Timing issue with helm pump.
Solutions
A. Confirm system has been bled free of all air. Refer to installation and
operating manual for filling and purging procedures.
B. Consult with selection guide and/or website to ensure proper cylinder
has been installed.
C. Check following:
a. Confirm tilt mechanism has been installed correctly.
b. Check all possible tilt settings.
4.7 Steering wheel(s) are bumpy
when turning either direction
NOTICE!
If the problem goes away in other tilt settings, replace tilt mechanism.
D. Replace and/or repair helm pump.
E. Replace and/or repair helm pump.
NOTE: A timing issue within a helm pump is very rare. Most timing related
problems are felt immediately after installation and purging.
WARNING!
Dometic does not recommend the disassembly of any helm pump.
Contact an authorized service center, or, replace helm pump.

13
EN
Causes
A. Air in the system (most common cause).
B. Dirt or debris in helm pump valves.
C. Internal bypass in steering cylinder and/or autopilot pump.
Solutions
A. Confirm that system is full of fluid and bled free of air. Refer to
installation and operating manual for filling and purging procedures.
B. Check fluid condition for signs of milky, dirty or contaminated fluid.
Flush system as noted on page 17.
C. Conduct the cylinder/helm pump test on page 20.
4.8 Boat dris to one side or the
other while underway
NOTICE!
On multiple helm applications, there is a possibility to enter a slow
freewheel situation if 1–helm is turned 1–direction and then the opposite
helm is slowly turned the opposite direction. This is normal and can be
stopped by performing a quick, partial turn of the wheel to fully close a
hydraulic valve.
NOTICE!
If helm/cylinder pass the test and there is not autopilot on board the boat
should be sea trialed while conducting the following test.
WARNING!
Dometic does not recommend the disassembly of any helm pump.
Contact an Authorized Service Center, or, replace helm pump.
CAUTION!
A system that is not responding must be diagnosed and corrected
prior to use.
Test
If possible, carefully take boat into an area free from obstruction.
• Run boat straight and then put in neutral. Do not turn wheel.
• Using a felt marker, mark cylinder shafts on both ends at gland seals.
• Do not turn wheel, bring boat up to a safe speed to determine if boat
veers off course.
• Shut down engine.
If the marks that you made did NOT move, this is a sign that the steering
system is holding course. In this case the steering system is not at fault.
Boat balance and hull design should be looked into.

14 EN
5 Power Assist system
troubleshooting
Causes
A. Mechanical interference.
B. Pro helm used with “unbalanced” cylinder.
C. Blockage or restriction in steering hoses between helm pump and
power assist pump.
D. Power Assist spool valve stuck or seized.
E. See advisory notice on page 27 for power assist pumps.
Solutions
A. Mechanical interference. See 4.2.
B.
A Pro helm cannot be used with an unbalanced cylinder. See section 4.2.
C. Mark and remove hoses from power assist pump. Pump 1/2 bottle of
steering fluid through helm and out of the hoses. If the wheel locks up
to one side only inspect the hose on that side of the system.
Status light on power assist is ON, electric motor does NOT run.
Causes
A. Fuse at battery or in rear of power assist blown.
B. Blown breaker.
C. Incorrect wiring to/from battery.
D. Low battery voltage.
E. Faulty electronics.
Solutions
A. Check fuse located at battery as well as fuses installed behind the rear
cover of the power assist pump.
B. Check all breakers for proper working condition.
C. Check that all wiring is correct and in good working order (consult
installation and operating manual).
D. Confirm all batteries are in good working order.
E. Test power assist voltage. Refer to page 29.
5.1 Steering wheel(s) “lock up” to
one or both directions
NOTICE!
The on status light on the power assist is triggered by the ignition lead.
If the fuse at the battery or, the fuses in the rear of the power assist are
blown, the status light will still be turned on or may turn to red. See how
to test the power assist unit on page 29.

15
EN
Causes
A. Air in system.
B. Faulty/damaged coupler.
Solutions
A. Bleed system as outlined in the power assist installation and
operating manual.
B. Inspect coupler for wear and/or damage (see inspection details below).
Inspection
• Turn ignition OFF.
• Disconnect power assist from battery.
• Loosen and remove two 5/16” hex head screws from top of power
assist motor.
• Lift motor straight UP. Hold top and bottom to ensure motor does
not come apart.
• Inspect coupling that joins the motor to the valve body.
• Replace if worn and/or broken.
5.2 Power Assist motor runs but NO
Power Assist
1
1
4
5
2
3
Figure 5-1.
Item Description
1 5/16” Hex Head Screw
2 Wire - Do not disconnect
3 0-Rings (x2) — Ensure O-rings
are in place prior to installation
4 Valve Body
5 Coupling — Install smaller slot
facing down towards the
valve body. Larger slot up
towards the motor

16 EN
Causes
A. Air in system.
$ Hoses between power assist and helm pump too short.
Solutions
A. Confirm that return line from power assist has been bled free of air.
Refer to power assist installation and operating manual for proper
filling and purging details.
B. Hoses installed between the helm pump and power assist should be
at least 6 feet long.
5.3 Bumpy feeling at steering wheel(s)
with Power Assist turned ON
NOTICE!
Above Causes and Solutions are under the assumption that the bumpy
feeling only happens when the power assist is turned on. For bumpy
feeling with the power assist on/off see section 4.7.