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1971duster340's avatar
1971duster340
Explorer
Dec 08, 2016

HWH motor runs, but no pressure

My Chariot coach has Series 625 HWH hydraulic levelers and 3~slides. They've worked flawlessly for 7 years, but all of a sudden nothing extends and I only hear the motor running (free spinning) when I try any of the hyd. systems. This sounds much like the system would if the hyd. fluid was low, but it's not and motor load sounds as if there is no hyd. pressure being built...a different hum as if there was air bubbles. The HWH is powered by the coach batteries and I see the normal drop in voltage when the motor spins.
I've tried removing/inspecting/installing the shuttle valve, then plugging the 'U' shaped pipe that pressures the manifold. Nothing changed after removing the non pressure end of the pipe to the manifold. That was supposed to take the levelers out of the hyd. circuit, but keep hyd. pressure to the slides. Last test was removing the pipe plug to see if the pump will pump fluid. It's gotta be the pump itself. Please explain how the motor is tied to the pump? All I've found is the motor/pump/reservoir ass'y has one part #, so I assume not to be sold individually.

Much Thanks
  • dougrainer's avatar
    dougrainer
    Nomad
    Dec 11, 2016
    1971duster340 wrote:
    Doug...This rectangular shaft, shear pin or however the motor torque gets to the pump sounds to be the culprit. I've gotten so lost in HWH's library of diagrams, so thanks for the URLs to the diagrams. Looks like the pump uses the gear driven method like an automotive oil pump, not a centrifugal or diaphragm pump. The General Manager at Chariot told me they had the reservoir siphon tube come loose on a coach, thus no fluid could be drawn from the reservoir tank.
    I'll report back when the Foretravel shop diagnoses the problem.


    While a Siphon tube "may" cause the problem, I doubt it. In over 30 years of working on HWH systems, I have never seen it. That Siphon Tube has a filter to prevent sucking in debris to the system. It is IMMERSED in the tank and if it came loose all that would happen is non filtered oil would be drawn into system. A GM would not know squat about operations of the systems on an RV. One of the reasons I hate to tell upper management about certain odd ball problems and the solutions are just like on these forums. You find and state the 1 out of a million causes and fixes and then a LOT of people then look for THAT cause as their problem and then post that so called solution is the fix. Doug
  • 1971duster340's avatar
    1971duster340
    Explorer
    Dec 11, 2016
    Doug...This rectangular shaft, shear pin or however the motor torque gets to the pump sounds to be the culprit. I've gotten so lost in HWH's library of diagrams, so thanks for the URLs to the diagrams. Looks like the pump uses the gear driven method like an automotive oil pump, not a centrifugal or diaphragm pump. The General Manager at Chariot told me they had the reservoir siphon tube come loose on a coach, thus no fluid could be drawn from the reservoir tank.
    I'll report back when the Foretravel shop diagnoses the problem.
  • dougrainer's avatar
    dougrainer
    Nomad
    Dec 08, 2016
    1971duster340 wrote:
    I have talked to HWH, but the system is beyond me other than those simple tests. Foretravel is close and they are a HWH Master Service Center. I'm going to turn it over to them, but I've heard (not from HWH) the entire ass'y has to be replaced. I am looking for some ammo if just the pump can be replaced.


    HWH uses a motor. On the end of the motor is a rectangular shaft drive pin that spins the manifold system pump. IF you remove the u shaped metal tube that is connected to the shuttle valve and run the pump, if NO fluid comes out (will be 3000 psi), then the odds are that shaft is broken. I do not know if HWH sells just that shaft or you have to buy the motor(which includes that shaft key). If you remove the motor, it will be evident if that shaft key is broken or the spring is bad that puts pressure on that shaft key to engage it. Doug

    The motor is sold separately. But, it depends on the brand/model motor. Some have been discontinued, even on a 7 year old motorhome. It was a vendor supply problem. Some older systems the motor cannot be purchased and you have to buy the Motor/Reservoir system. You transfer all the upper manifolds to the new pump/reservoir. Doug

    This link shows what the part looks like.


    http://www.hwhcorp.com/mr303311.pdf

    this link is for the Motor/Pump assblies.

    http://www.hwhcorp.com/mr30.html
  • 1971duster340's avatar
    1971duster340
    Explorer
    Dec 08, 2016
    I have talked to HWH, but the system is beyond me other than those simple tests. Foretravel is close and they are a HWH Master Service Center. I'm going to turn it over to them, but I've heard (not from HWH) the entire ass'y has to be replaced. I am looking for some ammo if just the pump can be replaced.
  • Y-Guy's avatar
    Y-Guy
    Moderator
    Dec 08, 2016
    Greg, have you visited their website? HWH Corp you can find some good support manuals but give them a call to, I hear over n over how good their support is.

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