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Troubleshooting

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Hoist Won't Go Up

Underbody Hoists

Do you have gear pump hydraulics?

Is the body overloaded for the capacity of the hoist?

  1. If the hoist has been overloaded the oil will go over the relief valve and not lift the load.
  2. One should observe how the load has been distributed. If the body is loaded heavy at the front this will diminish the overall lifting capacity of the hoist as well.

Has the hoist been properly maintained?

Confirm that all pivot points with grease zerks have been greased regularly. If a pivot point that is supposed to be greased has not been serviced regularly it is possible that the pin and bushing have gulled and that they are binding up.

Is the PTO working properly?

Confirm that the PTO is fully engaged and working properly.

For PTO problems or questions concerning the PTO contact the installer or business you purchased the unit from.

Does the reservoir have enough oil?

Check reservoir oil level. See the Operators Manual for fill instructions.

Is the suction line blocked or collapsed?

Remove and inspect the suction line hose for blockage or collapse. Remove the blockage or replace the hose as required.

Is the suction line free of air leaks?

There may be an air leak in the suction line preventing priming of the pump. Eliminate the leak by changing the hose or tightening/replacing the clamps.

Is the pump turning in the correct direction?

Confirm that the pump has the proper rotation. See the Operators Manual for instructions.

Is the cable pulling the valve spool to its full travel?

Check cable connections at the shifter and valve to make sure they are intact. Is the cable adjustment at the valve correct allowing the valve to fully shift? Check the Operators Manual for proper cable adjustment.

Are the hoses connected correctly?

Make certain that the hydraulic circuit is plumbed correctly.

  1. The pressure port of the pump is connected to the “inlet” port of the valve.
  2. For direct mount hydraulics, the “B” port is the power up and should be connected to the port at the base end of the cylinder, which is opposite the end of the cylinder shaft.
  3. In a double acting system the “A” port is the power down and should be connected to the port at the shaft end of the cylinder.
  4. The valve needs to have a return back to the tank.

Does the valve have the correct pressure?

Check the pressure on the power up side of the valve.

  1. On direct mount hydraulics, the “B” port is the power up side. Connect the hose that runs to the power up port of the cylinder directly into a pressure gauge (called deadheading). (Do not tee into the line with a pressure gauge. This would measure only the amount of pressure needed to raise the hoist with the amount of weight on it at that time).
  2. If the pressure is not at the recommended level adjust the pressure relief valve until the desired level is obtained. Check the appropriate specs of the equipment being powered by the valve for the recommended pressure setting.
  3. Loosen the jam nut on the relief cartridge. Turn the adjusting screw clockwise to increase pressure and counter-clockwise to decrease the pressure. If the pressure is okay, the cylinders internal bypass valve may be stuck open.

Is the internal bypass valve stuck open?

  1. To determine if the internal bypass valve is stuck open, remove the hose from the valve that comes from the shaft end of the cylinder.
  2. Put the end of the hose into a catch basin to collect any oil that might come out.
  3. Now try raising the hoist. If oil comes out of the loose end of the hose and the hoist does not go up the bypass valve is stuck open.

Hoist seems to raise extremely slow.

  1. Confirm that the valve cable is adjusted correctly as noted in the Operators Manual.
  2. DuraClass recommends a PTO ratio of 100-120% of engine speed.
  3. Confirm that the suction line is not obstructed in any way.

Do you have electric single or double-acting hydraulics?

What is the condition of the terminals?

  1. Make sure all of the terminals are clean and tight.
  2. Any corrosion should be removed from the terminals. Important: If a ground cable was fitted at initial install, remove and clean both the ground cable terminal and the aluminum base of the power unit. If a ground cable was not put in place at initial install, one should be added now.

What size battery cables should be used?

Battery cables should be a minimum size of 1“0”. If the cables are smaller than 1”0” they should be changed.

Is the battery in good condition?

  1. Using a Volt Meter, make sure the battery is charged and offering 12 volts at the unit. Low voltage can cause the unit to either not run or not run properly, due to the valve coils not energizing and, in turn, not shifting the valve.
  2. Using a Volt Meter, put the red lead on the “Hot” start solenoid post.
  3. Now touch the black lead to the motor case or a ground and read the volts.

Does the unit have a secure ground?

Check that the cable is attached to the threaded grounding hole on the side of the unit’s base. If it is not, one should be attached from this hole directly back to the negative post on the battery. Poor ground is the number one cause of trouble for these units.

Is the unit getting really hot?

If the unit is getting really hot when it is being operated, the unit does not have a secure ground.

  1. Place the red lead from the Volt Meter onto the unit’s aluminum base.
  2. Touch the black wire to a known ground.
  3. With the unit running, read the meter’s millivolts. The lower the reading, the better the ground is for the unit. Any reading above 2 volts would suggest that the unit does not have a good ground.
  4. For rated performance, the voltage at the power unit must be a minimum of 12 VDC. This should be measured between the large terminal of the start solenoid (where the battery cable is connected) and the base of the power unit.
    Note: Grounding of the power unit is just as important as the installation of the positive battery cable. It is easier to get a good ground by using a second battery cable.
  5. Connect the large terminal on the motor start solenoid to the positive terminal on  the battery with a 1”0” gauge battery cable.
  6. Connecting a second battery cable to the threaded hole in the power unit base  marked, “GRD” can complete grounding of the power unit.
  7. A size 1”0” cable should be attached to the battery negative terminal.
  8. Check the voltage between the large terminal on the start solenoid and the base of the power unit.

How do I check the motor start solenoid?

Eliminate the unit’s start solenoid, mounted to the motor, by using a jumper wire across the two large posts. This will supply power directly to the motor. If the motor runs, replace the solenoid. If the start solenoid is not energizing, it might be defective. It might also mean that the unit is not getting the proper voltage at the unit.

Is the cord plugged in securely?

Make sure the cord halves are securely plugged together. Something to look for here pertains to the pins on the end of the wire in the plug. If the wire can be pulled back toward the cord, it is not locked all the way into the sealed portion of the plug. If the pin is not all the way in, it might not be making contact as needed.

Is the body overloaded for the capacity of the hoist?

  1. If the hoist has been overloaded the oil will go over the relief valve and not lift the load.
  2. One should observe how the load has been distributed. If the body is loaded heavy at the front this will diminish the overall lifting capacity of the hoist as well.

Has the hoist been properly maintained?

Confirm that all pivot points with grease zerks have been greased regularly. If a pivot point that is supposed to be greased has not been serviced regularly it is possible that the pin and bushing have gulled and that they are binding up.

Does the reservoir have enough oil?

Check reservoir oil level. See the Operators Manual for fill instructions.

Is the hoist plumbed correctly?

Electric Single Acting:
On DuraClass’s electric single acting power unit the “C1” port is the power up and should be connected to the port at the base end of the cylinder, which is opposite the end of the cylinder shaft.

Electric Double Acting:

  1. On DuraClass’s double acting power unit the “C1” port is the power up port and should be connected to the port at the base end of the cylinder, which is opposite the end of the cylinder shaft.
  2. The pumps “C2” port is the power down and should be connected to the port on the cylinder towards the chrome shaft end of the cylinder tube.
  3. When the up button on the controller is depressed the coil on the valve in the “C2” port of the pump should become energized thus opening the valve. To confirm that the coil has become energized lay a screwdriver over the end of the coil. It should become magnetized.

Does the power unit have the correct pressure?

Check the pressure on the power up side of the valve. The “C1” port is the power up side.

  1. Connect the hose that runs to the power up port of the cylinder directly into a pressure gauge (called deadheading). (Do not tee into the line with a pressure gauge. This would measure only the amount of pressure needed to raise the hoist with the amount of weight on it at that time). If the pressure is less than 3000 PSI contact a DuraClass Customer Service Representative.
  2. If the pressure is okay, the cylinder’s internal bypass valve may be stuck open.

Is the internal bypass valve stuck open?

  1. To determine if the internal bypass valve is stuck open, at the valve remove the hose that comes from the shaft end of the cylinder.
  2. Put the end of the hose into a catch basin to collect any oil that may come out.
  3. Now, try raising the hoist. If oil comes out of the loose end of the hose and the hoist does not go up, the bypass valve is stuck open.

Have all pivot points been greased?

Confirm that the rear hinge and hoist frame have been greased. See Operators Manual for points of lubrication.

Hoist Won't Come Down

Underbody Hoists

Do you have gear pump hydraulics?

Is the PTO working properly?

Confirm that the PTO is fully engaged and working properly.

For PTO problems or questions concerning the PTO contact the installer or business you purchased the unit from.

Is the cable pulling the valve far enough?

Check cable connections at the shifter and valve to make sure they are intact. Is the cable adjustment at valve correct allowing the valve to shift fully? See the Operators Manual for proper cable adjustment.

Is the hoist free of obstructions?

Make sure that no foreign material has become lodged in the hoist frame preventing it from coming down.

Have all pivot points been greased?

Confirm that the rear hinge and hoist frame have been greased. See Operators Manual for points of lubrication.

How do I check the down side pressure of the valve?

Check the down side pressure in the same manner as the power up side pressure was checked. This pressure will be checked by deadheading from the valve’s “A” port. It should be approximately 500 PSI and 800 PSI.

Can I lower the hoist without hydraulics?

Prepare to try and lower the hoist manually.

  1. Secure the body while in the up position by using the body prop, blocking, and/or chain hoist.
  2. Once the body has been secured in the up position, remove the hose from the power up port of the valve (labeled “B”) and put it into a catch basin. Now you can remove the body prop and attempt to lower the hoist.
  3. If the hoist now comes down, the oil will run into the catch basin and the problem is in the valve.

What if the hoist will not come down without hydraulics?

If the hoist still will not come down, the problem is in the hoist frame, rear hinge, or possibly a bent cylinder shaft. You will now have to check further for galled pivot pins or a bent cylinder shaft.

Do you have electric single or double-acting hydraulics?

Is the hoist free of obstruction?

Make sure that no foreign material has become lodged in the hoist frame preventing it from coming down.

Have all pivot points been greased?

Confirm that the rear hinge and hoist frame have been greased. See Operators Manual for points of lubrication.

What is the condition of the terminals?

  1. Make sure all of the terminals are clean and tight.
  2. Any corrosion should be removed from the terminals. Important: if a ground cable was fitted at initial install, remove and clean both the ground cable terminal and the aluminum base of the power unit. If a ground cable was not put in place at initial install, one should be added now.

Does the unit have a secure ground?

  1. Check that the cable is attached to the threaded grounding hole on the side of the unit’s base. If it is not, one should be attached from this hole directly back to the negative post on the battery. Poor ground is the number one cause of trouble for these units.
  2. Using a Volt Meter, make sure the battery is charged and offering 12 volts at the unit. Low voltage can cause the unit to either not run or not run properly, due to the valve coils not energizing and, in turn, not shifting the valve.
  3. Using a Volt Meter, put the red lead on the “Hot” start solenoid post. Now touch the black lead to the motor case or a ground and read the volts.

Is the unit getting really hot?

If the unit is getting really hot when it is being operated, the unit does not have a secure ground.

    1. Place the red lead from the Volt Meter onto the unit’s aluminum base.
    2. Touch the black wire to a known ground.
    3. With the unit running, read the meter’s millivolts. The lower the reading, the better the ground is for the unit. Any reading above 2 volts would suggest that the unit does not have a good ground.
    4. For rated performance, the voltage at the power unit must be a minimum of 12 VDC. This should be measured between the large terminal of the start solenoid (where the battery cable is connected) and the base of the power unit.
      Note: Grounding of the power unit is just as important as the installation of the positive battery cable. It is easier to get a good ground by using a second battery cable.
    5. Connect the large terminal on the motor start solenoid to the positive terminal on the battery with a 1″0″ gauge battery cable.
    6. Connecting a second battery cable to the threaded hole in the power unit base
      marked, “GRD” can complete grounding of the power unit.
    7. A size 1″0″ cable should be attached to the battery negative terminal.
    8. Check the voltage between the large terminal on the start solenoid and the base of the power unit.

Is the cord plugged in securely?

Make sure the cord halves are securely plugged together. Something to look for here pertains to the pins on the end of the wire in the plug. If the wire can be pulled back toward the cord, it is not locked all the way into the sealed portion of the plug. If the pin is not all the way in, it might not be making contact as needed.

Is the solenoid valve working correctly to lower the hoist?

  1. When the down button on the controller is depressed the coil on the valve in the “C1” port of the pump should become energized thus opening the valve to allow the hoist to come down. To confirm that the coil has become energized lay a screwdriver over the end of the coil. It should become magnetized.
  2. There needs to be at least 10 volts at the coil for it to work properly.
  3. If the coil is becoming energized and the hoist still will not lower, you potentially have a contaminated valve or bent valve stem that will need to be replaced.
  4. The valve stem can be checked by loosening the coil and spinning it around the stem. If it wobbles or moves up and down as it spins, the valve stem is bent.
  5. If contamination is found on the valve screens, this can prevent the valve from shifting properly.
  6. If the coil is not being magnetized it needs to be replaced.

Is the hoist plumbed correctly?

Double Acting Hydraulics:

  1. On DuraClass’s double acting power unit the “C1” port is the power up port and should be connected to the port at the base end of the cylinder, which is opposite the end of the cylinder shaft.
  2. The pumps “C2” port is the power down and should be connected to the port on the cylinder towards the chrome shaft end of the cylinder tube.
  3. When the down button on the controller is depressed the coil on the valve in the “C1” port of the pump should become energized thus opening the valve to allow the hoist to go down. To confirm that the coil has become energized lay a screwdriver over the end of the coil. It should become magnetized.

What if the hoist will not come down without hydraulics?

If the hoist still will not come down, the problem is in the hoist frame, rear hinge, or possibly a bent cylinder shaft. You will now have to check further for galled pivot pins or a bent cylinder shaft.

Can I lower the hoist without hydraulics?

Prepare to try and lower the hoist manually.

  1. Secure the body while in the up position by using the body prop, blocking, and/or chain hoist.
  2. Once the body has been secured in the up position, remove the hose from the power up port of the valve (labeled “B”) and put it into a catch basin. Now you can remove the body prop and attempt to lower the hoist.
  3. If the hoist now comes down, the oil will run into the catch basin and the problem is in the valve.

Direct Mount Gear Pump

Why does the pump seem to be running noisier?

  1. Check the reservoir oil level to see that it is sufficient as noted in the Operators Manual.
  2. Remove and inspect the inlet hose for blockage and replace as needed.
  3. Clean or replace the reservoir breather cap.
  4. Possibly the oil is too thick. Change to a lower viscosity.
  5. Be sure the suction and return lines are well submerged in the reservoir.

What do I do if the pump is overheating?

  1. Disengage the pump PTO when traveling.
  2. Possibly the oil is too thick. Change to a lower viscosity.
  3. There may be an internal leak due to wear. Replace pump as required. Check cleanliness of oil, replace if dirty.

The pump is leaking externally?

Replace pump as required. Check cleanliness of oil, replace if dirty.

Cylinder is Leaking

Underbody Hoists

What pressure is the cylinder being tested at?

  1. Confirm that the cylinder is not being tested at more than its rated pressure. To find your hoists rated pressure check the Owners Manual. Testing at a higher pressure could damage the cylinder or be the cause of the leak.
  2. Clean the cylinder thoroughly so any fresh oil may be easily seen while testing.
  3. Check all connections and fittings to see that they are tight and that none are cracked.
  4. After the cylinders have been cleaned, pressurize them for a few seconds at a time. If there is a leak, it should be easy to locate where the oil is coming from.
  5. If leaking determine if the oil is coming from the shaft seal, around the threads, or from a defective weld.
  6. If the oil is coming from a pinhole in the weld of one of the cylinder ports or around the base plate weld, contact DuraClass for technical assistance.

Telescopic Hoists

What pressure is the cylinder being tested at?

  1. Confirm what pressure the cylinder is being tested at. See the Owners Manual at our website for appropriate cylinder pressures.
  2. Clean the cylinder thoroughly so any fresh oil may be easily seen while testing.
  3. Check all connections and fittings to see that they are tight and that none are cracked.
  4. Check the air bleed valve, if the cylinder is equipped with one. Tighten the valve cap to make sure the valve is fully closed. If oil is leaking from around the base of the valve, tighten the valve body to seal off the NPTF threads. Care should be taken not to over tighten the valve, causing the valve body to break off.
  5. Check each sleeve stage for oil leaking from the wiper. If this is the case, the main oil seal has somehow been damaged or the stage has been over-pressurized. There is no adjustment possible. Check any cylinder welds for oil leakage. If there are any leaking welds, replace the cylinder.
    1. Look at the sleeve surfaces to determine if there are any scratches or dents that may have damaged the internal oil seal. Determining the condition of the sleeve surfaces will help decide if the cylinder can be repaired of needs to be replaced.
    2. Check to see what pressure rating the system is running at. The system pressure may be or was too high and caused the cylinder to swell in the seal area. The swelled area will be too large for the main seal to seal off. The cylinder will have to be replaced.

Telescopic Cylinder

Telescopic Cylinder Chatters

Why does the cylinder seem to chatter or vibrate?

  1. The first thing to check is the cylinder alignment. Excess friction due to misalignment can cause cylinder chatter. Check to see if the cylinder is mounted and aligned correctly. Correct any mounting or alignment problems.
  2. Check for air in the hydraulic system. Most cylinders have an internal auto-bleed design. Follow the initial start-up procedure to bleed the cylinder of air. Look for any other places where air might be introduced into the system, such as the pump inlet line. Seal off any leaks in the system.
  3. Check fluid level in the reservoir to make sure the system has enough fluid to extend the cylinder completely. Add fluid as needed.
  4. Check that the reservoir air breather is not blocked. If the breather appears dirty, replace or clean the breather.
  5. Confirm that the pump capacity is large enough for the system and body requirement. See the Owners Manual.
  6. Check that the pump is functioning, moving oil, and not worn. The gears inside a pump can wear over time. When the gears wear there is more room around the gear allowing oil to just move around inside the pump meaning that there is less oil being forced out of the pump. To check the amount of oil flow a flow meter can be installed in the line.
  7. Check that unloading or relief valves are not misadjusted. These valves may be set too low and bypassing some of the pump flow. Check the Owners Manual, for proper relief valve setting.
  8. Check for excessive back-pressure on external drain valves. Should the pressure be too high look at plumbing the lines directly back to tank.
  9. Check for any check valves in the system and confirm that they are working properly.
  10. The main control valve may have a broken spring controlling the valve spool. Check that the spring is good and that the control valve is working properly.
  11. The cylinder may be sized too close to the load requirement. Either reduce the load or install a larger cylinder.
  12. The cylinder may have internal damage. A determination must be made as to how to have the cylinder repaired or replaced.

Telescopic Cylinder Mis-staging

  1. Following are some possibilities that could account for a cylinder mis-staging. First check that all of the air has been removed from the cylinder. Cylinders with the internal auto-bleed design should bleed the air out automatically by cycling the cylinder several times. If equipped with a manual air bleed valve, follow the air bleed procedure to remove entrapped air. The procedure for manually bleeding a telescopic cylinder is in the Owners Manual.
  2. Mechanical frictional force is another cause of cylinder mis-staging. Because of the seal design used, there is no adjustment required to the seal. Therefore, should mis-staging occur adjusting the retaining glands would not have any affect. Inspect the cylinder stage sleeve for straightness. A bent tube will cause added friction between moving parts. If any parts are bent, replace the cylinder.
  3. Check to see what pressure rating the system is running at. The system pressure may be or was too high and caused the cylinder to swell in the seal area. Upon retracting the cylinder, the swelled area will be forced into the next larger stage. These two stages may, then, be stuck together and not be able to extend. Inspect the sleeves for swelled areas and, if found, replace the cylinder.

Telescopic Cylinder Will Not Come Down Completely

  1. The first thing to check is that there is nothing mechanically holding the dump body up. Remove any obstructions that keep the body from coming down.
  2. Mechanical frictional force is something that could hinder a cylinder from coming down completely. Because of the seal design used, there is no adjustment required to the seal. Therefore, should sticking occur, adjusting the retaining glands would not have any effect. Inspect the cylinder stage sleeve for straightness. A bent tube will cause added friction between moving parts. If any parts are bent, replace the cylinder.
  3. Check to see what pressure rating the system is running at. The system pressure may be or was too high and caused the cylinder to swell in the seal area. Upon retracting the cylinder, the swelled area will be forced into the next larger stage and not allowed to fully retract. These two stages may, then, be stuck together and not be able to extend. Inspect the sleeves for swelled areas and if found, replace the cylinder.
  4. Check that the reservoir air breather is not blocked. If the breather appears dirty, replace or clean the breather.
  5. Check that the hydraulic components are working properly and not hydraulically locking the cylinder up.
  6. Cylinders with internal auto-bleed design may have internal damage. Determine this cause by eliminating all the other possibilities.

Air Tailgate Cylinder

The cylinder does not extend or retract

  1. First, check to see that there is 12VDC present at the switch. If there is no voltage, check the voltage at the source for the switch and termination points.
  2. Assuming there is 12VDC at the switch, check for 12VDC at the valve. If there is not voltage at the valve, check the wiring from the switch to the valve.
  3. Assuming there is 12VDC at the valve, check the air pressure. If there is no air pressure check the main air supply.
  4. If the air pressure is over 120 PSI add a regulator kit.
  5. Make sure the cylinder is disconnected from the body. If the air pressure is 120 PSI or less, pushing the manual override button will check the valve. The manual override is located on the back of the solenoid and can be pushed with a pen or a small screwdriver. If the valve is functioning properly the cylinder will extend when the manual override is pushed.
  6. If the valve is working, check the cylinder. What is the condition of the rod? There can be a few things that can affect the rod. Make sure that the rod has not been painted. Also, check to see if the rod has been bent. Another check is to make sure the clevis pins are still in place.

The Valve is not working

  1. More often than not, the valve will be working correctly. There may be cases where the solenoid went bad or there is contamination inside the valve causing it to stick. It is more likely that there is a bad connection to the solenoid.
  2. Make sure the cylinder is disconnected from the body. The cylinder will extend when the manual override is pushed. Check to make sure the wires are connected. If they are, check the manual override. If the cylinder retracts, then the solenoid is bad.

The cylinder is leaking

  1. All air valves will have a small amount of leakage. This should not result in any performance loss of the cylinders.
  2. The first thing to do is to check that all air lines and fittings are intact.
  3. Make sure the truck air pressure is less than 120 PSI, as this could account for some leakage.
  4. Spray the valve at the mufflers with soapy water. If there are air bubbles present, there could be a leak in the cylinder or valve.
  5. Make sure that the shop air pressure is less than 120 PSI. On a bench, take the valve off the cylinder and run the shop air pressure into the cap end of the cylinder. The cylinder will extend. Listen for leaks. If you can’t hear anything, the cylinder is good.
  6. Send the valve back for evaluation.

Vibrators

Why won't my vibrator run?

  1. Confirm that the power source is connected to the vibrator.
  2. Confirm that all connections are intact and secure.
  3. Check to see if there is current at the switch and at the vibrator.
  4. Check to see that the unit is grounded properly.
  5. If ground wire is good remove the vibrator from its mount and clean off any paint, rust, etc. from mounting surface.
  6. Add a ground strap from the vibrator to the chassis frame.

Why does my vibrator seem to be noisy?

  1. Check to see that all mounting bolts are installed and tight.
  2. Check to see that all welds are intact on the mounting assembly.
  3. Check if the abnormal noise is coming from the inside of the vibrator.
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