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Williams Controls · Air System
118181
In stock · ships from Knoxville
This is a pressure protection valve designed to safeguard the primary air system on a heavy-duty truck or trailer.
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Verified fitment for 2 applications
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All confirmed applications for this part number.
Other applications
Other applications
This is a universal inline component based on industry-standard specs (70 PSI open/close, FMVSS121 compliant). Actual fitment depends on port size and plumbing configuration. Some installations may require plumbing changes when replacing older valves.
Part data verified against 5 catalog sources
Numbers this part supersedes or interchanges with. Showing 2 of 2.
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It remains closed to block airflow until the supply pressure builds up to a nominal 70 PSI, at which point it opens to allow air into auxiliary systems. If the primary system pressure drops below 70 PSI due to a leak or failure, the valve automatically snaps shut. This prevents the loss of braking air pressure from the primary tanks, ensuring your service brakes remain functional during roadside emergencies.
Part Number: 118181
WM778A 70PSI PRESSURE PROTECTION VALVE
Unit: ea
Dealer: Post Onsite
Compatibility, alternatives, and more
Parts commonly needed alongside air system
