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steering assist
I have an 05 H3-45 chassis. Lately, the steering assist has been intermittant. Prevost has checked out the pump pressures at the engine and found no problems.Therefore the PS pump is OK. With the front wheels lifted, turning the wheels lock to lock, proved there is no suspension interference. This leaves, by default, only the steering box as the problem area. This hard steering issue has surfaced before and then self corrected. Upon leaving Prevost yesterday, it seemed to have magically corrected as I was driving away. Approximately 100 miles later, at slow speed, the hard steering was back. The system must be working partially because at dead stop the steering wheel can be turned lock to lock, but with difficulty. I know of the subsystem where, electrically, the steering assist is minimized at highway speeds.Could this subsystem be malfunctioning and causing my problem? Does anyone have any similar experiences and hopefully solutions?
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6 Replies
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Les,
I moved your post here so we can get Prevost involved with your steering issue.
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The box should work so that the steering has full pump pressure at low speeds and the assist is lessened as the speed increases. This is so you get more “road” feel at higher speeds.
The system works with an ECU (electronic control module) which is located in the front electrical compartment below the driver’s window. It looks like a tall relay but it has ZF on the marking on the outside of the unit. This ecu plugs into a relay base and can be removed by pulling it up.
The box receives pwer and ground and a speed signal from the chassis and there is a two wire harness that goes from the unit to the connector on the steering gear box. The system works by varying the signal on the wires to the steering gear and causing the steering gear to bypass assist presssure.
First check to see that the unit is well installed and there are no backed out pins in the ECU base and that the connector at the steeering gear is well connected and the harness appears to have no defects.
If you remove the ECU from its base and you drive the vehicle you will find reduced power assist across all speeds as it defaults to a mid range. Therefore it would require more effort to turn the steering at low speeds and reduced assist at all speeds up the speed range. If you do this you can find out if the lack of assist you feel is what yoiu then would feel with the module removed. It may be that the connections are not good or open as the vehicle heats and the circuits heat and it opens the circuit and you loose the normal assist.
Try it and see.
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Les,
Let us know how all this works out.
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Understand– will check relay. Also remove it and try a test. Thx for suggestion.
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My steering problem has been solved. While attending the Prevost Prouds rally in Branson, the Prevost service techs took the time to check out the ZF control module thoroughly. Connections were checked and then voltages to make sure up to specs. Culprit was a bad ground wire and by moving it to another electronic ( home run to battery bank ) ground solved the intermittent issue. My chassis is an 05 pre- multiplex model. Newer models apparantly do not have this same steering assist. One additional recommendation by Prevost was to replace the old inline glass fuse that powers the module with the newer plastic tab style of equal amperage. Reasoning is that the spring loaded glass case fuse type can lose contact and mimic the problem.
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