THE HYDRAULIC SLIDE OUT SYSTEMGENERAL OPERATION & TROUBLE SHOOTING NOTESThe hydraulic slide-out system is a fixed displacement system, using double acting hydrauliccylinders to open and close a room assembly built into the travel trailer or motor home.Cylinders are energized by a 12 volt DC high pressure hydraulic pump through electricallyoperated directional valves. The pump is supplied the 12V power from the vehicle’s batterycircuit.A wall mounted, three (3) position momentary switch activates the room movement. For safetypurposes, the switch must be pressed continuously during the room movement.Operation of the systemWhen the momentary switch is held to activate the 12V motor, it closes the solenoid valvecircuit. This causes the pump to start and simultaneously shifts the valve. Fluid is pumpedthrough the valve and into the cylinder ports. Depending on the switch position, the room willeither move to extend or retract to the home position.When a single cylinder is used in the system, the cylinder becomes a part of the reservoir fluidvolume. As the cylinder extends, the fluid is pumped from the rod end of the cylinder to thebase end. The extra fluid needed to fill the base end of the cylinder is pulled from the reservoir.As the room is retracted, the fluid moves from the rod end to the base end. The extra fluid isreturned to the reservoir.When two cylinders are used in tandem to move the room, one cylinder is called the “Master”and the other is called the “Slave”. NOTE: in this system the oil between the two cylindersnever goes to the reservoir. This is the most important feature that the repairman ortroubleshooter must understand when diagnosing or repairing this type of system. The Mastercylinder (the larger cylinder) receives fluid from the pump into the rear port, which causes it toextend. As this cylinder extends, it pushes the fluid from the front port out. The fluid movesthrough a hose that is attached to the rear port of the Slave cylinder, which causes it to extend.The fluid from the front of the Slave cylinder is pushed out of the port and moves through ahose that returns the fluid back to the pump and reservoir. When the process is reversed toretract the room, the pump will send fluid through the hose to the front port of the Slavecylinder. As the fluid enters the front port, it will force the room to close. As the Slave cylinderretracts, the fluid at the rear will be forced to the front port of the Master cylinder. It will thenbe retracting at the same rate as the Slave cylinder and the room will evenly close. The fluidfrom the rear of the Master cylinder will be returned to the pump and reservoir. For a betterunderstanding of how the system functions, refer to illustrations HS-1 thru HS-4 following thissection.
NOTE: The typical installation of the Hydra-Slide System assembly is to assemble the largerdiameter Master cylinder toward the front of the vehicle and the Slave cylinder toward the rear.All illustrations show the system set up in this configuration. Identify the Master and Slavecylinders on your travel trailer by measuring the outside diameter of the body. The Mastercylinder will be 1 7/8” diameter and the Slave cylinder will be 1 ¾” diameter. When removingcylinders for replacement, make certain that the Master and Slave cylinders are replaced in thesame slide tube from which they were removed.The early Production of this system proved to be unreliable for two reasons:1. The room would drift out while driving to or from a location. This problem was “fixed”by placing a Check Valve in the system, as noted in the following paragraph.2. As fluid would be “lost” from the hose between the Master and Slave cylinder, the roomwould not close evenly. As the room would extend, the front of the room would get aheadof the rear. As the room would retract, the rear of the room would retract ahead of the frontof the room. If this condition is not corrected, the room will be damaged. This problem wasinitially solved by the addition of a small in-line check valve, and was eventually replacedby a Phasing Valve mounted directly on the pump. Custom Cylinders International, Inc.has developed a pump system that eliminates the add-on valve by integrating a speciallogic circuit to check the volume of fluid between the Master and Slave cylinders on eachactivation cycle.FOLLOWING ILLUSTRATIONS REPRESENT 3 HYDRA-SLIDE FLEETWOODTRAVEL TRAILER- 2 CYLINDER ROOM CIRCUITSILLUSTRATIONHS-1
MANUAL CLOSING OF ROOMMost systems will use a Check Valve that blocks the reverse flow of fluid to keep the roomclosed. As a safety precaution there are usually mechanical locks to hold the room in placeduring transit on the highway.Should it be necessary to manually retract the room due to pump failure or some other problem,remove the hose at the pump that supplies fluid to the rear port of the Master cylinder and placeit in a container to catch a considerable amount of fluid. Remove the hose at the pump thatsupplies fluid to the front port of the Slave cylinder. Attach a come-along to the door-sidemainframe and the other end to the end of the Slave slide tube. See diagram number HS-5. Asthe room is gradually forced in to the closed position, fluid will move from the Slave cylinder tothe Master cylinder and force it to retract.ILLUSTRATIONHS-5
Electrical system maintenanceFor optimum performance, the slide out system requires full battery current and voltage. Thebattery must be maintained at full capacity. Other than good battery maintenance, check theterminals and other connections at the battery, the control switch, and the pump motor forcorrosion, tightness, or damage. Check motor leads under the trailer or motor home chassis.Since these connections are subject to damage from road debris, be sure they are in goodcondition.Mechanical maintenanceAlthough the system is designed to be almost maintenance free, actuate the room once or twicea month to help keep the seals and internal moving parts lubricated.The best time to check for external leaks in the system is when the unit is moved from theparking spot, by looking for any signs of hydraulic fluid.Hydraulic system troubleshootingThe hydraulic system is only one of several interrelated slide out room system components.When something restricts from travel on front, rear, or both, system performance will beunpredictable. It is very important that both cylinders are allowed to travel full distance (fullstroke). Remember that the hydraulics are tied very closely to the electrical system and oneproblem might appear to be a hydraulic problem and will actually be an electrical issue.Testing for hydraulic valve performanceThis test will check for operation of the phasing valve. Perform this test with extreme caution ordamage can occur to the room. Never allow the room to run more than two inches out ofalignment.When retracting the room place a 12” to 14” long 2X4 between the chassis and S1 slide tube,and flange end (flange that support the room). This will restrict the front cylinder in movementand allow the back to continue to move. DO NOT ALLOW A MISALIGNMENT OF MORETHAN 1 TO 2 INCHES. DAMAGE CAN OCCUR TO THE VEHICLE AND ROOM.After misalignment has occurred, stop and measure both front and rear extension. Let room setfor a couple of minutes and re-measure. If there is movement, check for leaking fittings. If nomovement, extend room to full open position, (be sure to allow room to realign itself) andmeasure. Let set for a few minutes and then re-measure. If there is no movement, retract andcheck to see if room is sealed. Note: it is normal for the front of the room to run ahead of rearone half to three quarter inch before closing. Be cautious that the misalignment does not causeany damage to interior room. When fully extended, the room should realign itself. If it does notrealign, it may be required that the pump pressure be set a little higher. CAUTION: DO NOTSET THE PUMP PRESSURE HIGHER THAN 1800 PSI. Operate room through at least twocomplete cycles to make certain that the front and rear are in alignment during travel and stopsimultaneously. Test is now complete.
NOTE: It is OK for the front to stop first and the back to travel one halfto three quarter inch before closing. It is not OK for the back to stop first. This will causethe front to not close fully. Cycle the room one more time to see if this corrects themisalignment.Electrical troubleshootingSince there are very few serviceable parts for the pump, motor, or reservoir, electricaltroubleshooting and service by the owner is limited to thorough checking of wiring andconnections. Loose connections or broken wiring tends to be the most common problemsassociated with the electrical system. CCI initiated an Engineering program in early 2009 todevelop an electrical replacement parts inventory of Hydra Slide System components. If theowner can not determine the problem, it may be necessary that a qualified RV service center orautomotive electrical continue the diagnosis.Since there are no records available for the Hydra Slide System circuits and spare parts list, itmay be necessary to send the travel trailer’s or motor home suspect part to CCI for reverseengineering to find or develop a replacement. This type of activity has already resulted in thedesign and manufacture of a relay circuit board that was no longer available. There is nocharge for this service.System troubleshooting guideThe following guide outlines some of the common problems of the Hydra Slide system, thecauses, and possible corrective actions. This is not a comprehensive listing, but will provide theService Tech basic information. See Illustrations HS-6a and HS-6b.Motor/control/reservoir troubleshootingBefore attempting to troubleshoot the motor/pump assembly, be sure an adequate power sourceis available. The trailer batteries should be fully charged or the unit should be plugged into A/Cservice with batteries installed. Do not attempt to troubleshoot the motor/pump assemblywithout assuring full electrical system capacity.The following tests require only a DC volt meter (or 12 volt DC test lamp) and a jumper lead.Hydra-Slide hydraulic systems troubleshooting guideThe following troubleshooting chart outlines some of the most common problems associatedwith the Hydra-Slide recreational vehicle room slide out hydraulic systems.1) ROOM DOES NOT MOVE WHEN SWITCH IS PRESSEDa-The travel locks are still in placeRemedy Remove travel locksb-Low battery voltage, blown fuse, defective wiring
Remedy Check battery charge condition. Charge battery or add auxiliarypower source.c-Motor/pump not functioningRemedy See “MOTOR/PUMP/RESERVOIR TROUBLESHOOTING”notes.2) PUMP RUNS, BUT ROOM DOES NOT MOVEa-Shuttle valve is not shifting fluid directionRemedy Check wiring to valve. Wires may be reversed or damaged. Remove valve, clean, check for damageto seats or seals. Verify relay is operative. Replace valve or relay3) PUMP RUNS, BUT ROOM MOVES SLOWLYa-Low battery, poor ground, extremely low outdoor temperature.Remedy Charge battery to full capacity or replace Verify ground connection at battery post and to the vehiclechassis. Allow system to warm up.b-S2 (rear hydraulic cylinder) is leaking at Port.Remedy Tighten fitting or replace if damaged.c-Gap between jam nuts to large.Remedy Reduce gap. CAUTION: Room must be completely closed or openwhen adjusting. Both cylinders must close and open within 2” or room couldbe damaged.4) THE FRONT OF THE ROOM WILL DRIFT OUT IN THE CLOSED POSITIONa-Leak in line between S1 (front cylinder front port) and S2 (rear cylinder).Remedy Check fittings for leaks and tighten.b-Cylinder has internal bypass around the piston.Remedy Repack or replace cylinder.ILLUSTRATIONHS-6ac-Room roller is damagedRemedy Replace roller.d-#3 or #4 hose from pump is leaking at pumpRemedy Check all fittings at pump for leaks & tighten.e-Contamination in valve bodyRemedy Cycle room in & out to clear.5) THE BACK OF THE ROOM DRIFTS OUT WHEN IN THE CLOSED POSITIONa-#1 or #2 hose from pump is leaking at pumpRemedy Check all fittings at pump for leaks & tighten.
ILLUSTRATIONHS-6bMOTOR/CONTROL/RESERVOIR TROUBLESHOOTING & REPAIRBefore attempting to troubleshoot the motor/pump assembly it is mandatory that an adequate12V poser source is available. The trailer batteries must be fully charged or the vehicle beattached to AC converter with batteries installed. Do not attempt to troubleshoot the systemwithout adequate, full, electrical system capacity.The following tests require only a DC voltmeter (or 12V DC test lamp) and a jumper wire.Attach voltmeter (or test light) leads to the negative and positive switch terminals. Does themeter indicate 12V DC?YESNOCheck all connections between battery andswitch. Check fuse and replace, if necessary.Recheck as above.At the motor, check incoming leads for 12V DC (if necessary, disconnect leadsat the wire splices). Does the meter indicate 12V DC?YESReplace the motor. The motor isnot field serviceable. Do notattempt to repair it.NOCheck all wires and connections betweenthe wall switch and motor. Repair orreplace connections as required. Retestas above.
Electrical troubleshootingSince there are no field serviceable parts in the motor or pump/reservoir, electricaltroubleshooting and service is limited to replacing only those components as previouslyoutlined. Thorough checking of wiring and connections is the only other electrical service thatcan be performed. Generally replacement parts are limited to motors, solenoids, relays, andcircuit boards. Contact the Engineering Department for additional information, or to reverseengineer a component.Thorough checking of wiring and connections is the only other electrical service that can beperformed.SERVICE PARTSRefer to HS-8 for available service parts.DEVELOP PARTS LIST AND DRAWING OF TYPICAL PUMP/RESERVOIR FORILLUSTRATION HS-7
THE FOLLOWING EXCERPTS WERE REPRODUCED FROM A FLEETWOOD MOTORHOME SERVICE BULLETINHYDRA-SLIDE CORPORATIONEZ-GLIDE MOTOR HOME SYSTEMUSED ON ALL FLEETWOOD MOTOR HOME VEHICLESHYDRAULIC CYLINDER TEST PROCEDURESThe following steps have been established to determine a defective hydraulic cylinder that hasan internal fluid bypass condition (fluid bypassing the piston seal) or leaking externally at thechrome rod seal (fluid leaking around the rod where it moves in and out of the cylinder body) atthe front of the cylinder. This test is performed with the cylinder installed on the EZ-GlideSystem and the room in its full retracted “IN” position.CAUTION-Protective safety glasses are to be worn while performing this test. THE SYSTEMOPERATING PRESSURE IS 1500 POUNDS AND A LEAK CAN PENETRATE THESURFACE OF THE BODY, WHICH CAN CAUSE SEVERE INJURY.1) Locate the hose attached to the rear of the hydraulic cylinder. Trace this hose up to theconnection at the hydraulic pump.2) When you have located where the hose is connected to the pump, disconnect this hose atthe pump connection, using a 9/16” open end wrench. CAUTION: Pressurized fluid mayflow out until the system is relaxed. This is a normal condition for a hydraulic system thathas been under operating pressure.3) Using a container, place the hose end into the container to catch the fluid that was insidethe hydraulic hose. Catching the fluid will not only protect the environment but will alsokeep the oil mess off the equipment and out of the work area.4) The next step will require and additional person. This helper will be used to operate thepower switch of the EZ-GLIDE system. With the hose inside the container, activate theswitch of operate the room (to move the room “IN”). At this point fluid may flow in theamount of 3 to 4 tablespoons into the container. This would be a normal event and is nota defect.5) If the piston seal is defective, there will be a continuous flow of fluid out of the end of thedisconnected hose.6) If the rod seal (where the chrome rod comes out of the front of the cylinder) is defective,there will be a spray or continuous leak at the front of the cylinder.7) The cylinder will need to be replaced ONLY is fluid is flowing as described in #5 or #6.If fluid is not flowing, the cylinder is operating to specifications and does not requirereplacement.8) This system has only 1 hydraulic cylinder that operates the room slide-out. Whenreplacing this cylinders, order part #141625-15H.
If no defects are found in the hydraulic cylinder, the next logical step to check is thepump/manifold assembly. The majority of problems are then isolated to the check valve.Remove and clean the check valve, looking for damage to the ball or seat and any debris thatmay be keeping it from fully seating.Custom Cylinders International Inc. provides repair service for most brands of hydraulicsystems used in the RV, industrial equipment, and general industrial industries through thesister company Custom Cylinder Repair Service, Inc.