the saftey valve is a last resort for the air system,
there should be another valve on or very near to the compressor which is tubular in shape with a plastic cover on the top this is the govenor valve which tells the compressor when to stop building the air up and when to begin building the air again these valves are prone to failure when the get clogged with soot from the air system
hope this helps
daffy4
July 2010
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