Hendrickson has coupled a Haldex PR Plus valve when building its suspension systems, to great success.
The Haldex PR Plus valve is a no-delay design, featuring a tight dead zone and a reliable ceramic seal valve design.
Hendrickson technicians have found this Haldex valve to be highly versatile, where it can be truck mounted in almost any position.
So that the Haldex can be positioned in a range of different positions, its arm is supplied separately, meaning that, ultimately, there are 16 possible variations of HCV, shaft and arm positions.
It is essential that the arm is installed in the correct orientation to the bump identifier dimple, according to the valve’s mounting position.
Incorrect orientation can cause the suspension height and valve operation to behave unpredictably.
This procedure often catches technicians out during installation. When replacing an existing valve, the easiest technique is to copy the arm and bump position of the old one that is being replaced.
Alternatively, installation details are usually provided with the valve, and simplified instructions can be found on the Hendrickson website in technical bulletin 49441-311.
Another key point to remember with the Haldex HCV is the location of its air vents.
Suspension dump vent
This vent is located under the plastic cover at the rear of the HCV.
Because of this design, it is not possible to add a pressure regulating valve to the dump port to keep residual pressure in the air springs when dumped.
However, residual pressure can be set up by a couple of other arrangements, such as bypassing the HCV and using a separate solenoid and regulator for the dump function.
Suspension height adjusting vent
This is located at the valve shaft. Despite being an inherent part of the design, air venting from the shaft area is often mistaken as a leak by technicians unfamiliar with Haldex HCV operation.
For example, after driving a truck into the workshop, a technician may notice air escaping from the valve shaft before the suspension has fully settled, often resulting in the frequent response by technicians stating that “The HCV is leaking”.
However, the most likely reason is that the suspension is just a little high and needs a minute or so for the valve to vent excess air until it is at the correct ride height.
Therefore, the best approach is to allow the valve a couple of minutes to settle before rechecking for leaks.
A little extra care on installation will save the technician many headaches, and giving the suspension time to settle will save time and money on replacing valves that were working correctly.
Therefore, when serviced with proper understanding of the situation and care, height control valves will remain a reliable, essential and fully operational part of heavy vehicle air suspension systems.
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