Governor signal line

Discussion in 'Ask An Owner Operator' started by 77fib77, Dec 1, 2023.

  1. 77fib77

    77fib77 Road Train Member

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    So I have a truck that has the purge valve always going off. But it just started doing that.

    I took off the signal line. Air comes out near the governor. Plug it in poof, it purges. Is there always supposed to be air in signal line? When it drops below 100 psi, the air stops and the compressor kicks back in?
     
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  3. JB7

    JB7 Medium Load Member

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    The air in the signal line holds open the unloader valve when the pressure is high enough, about 120 -130psi. That way air is not pumped to the tanks when it is not needed. Once the pressure drops to about 100 the air is shut off allowing the unloader valve to close and the compressor to pump air to the tanks.

    Constant purging - these may vary depending on the make and model of dryer. What do you have?
    Excessive leakage
    Defectjve delivery check valve
    Defective governor
    Compressor unloader leaking excessively
     
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  4. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    A pic of the governor and air dryer would make helping you easier.
     
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  5. JB7

    JB7 Medium Load Member

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    Below provides more detail.
    "Is there always supposed to be air in signal line? " No
    upload_2023-12-1_22-43-49.png
    As the system reservoir air pressure drops to the cut-in setting of the governor, the force exerted by the air pressure on the piston will be reduced so that the pressure setting spring will move the piston down. The inlet valve will close and the exhaust will open. With the exhaust open, the air in the unloader line will escape back through the piston, through the exhaust stem and out the exhaust port
     
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  6. 77fib77

    77fib77 Road Train Member

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    Well the signal line was cracked going into the air compressor. So the system cycled quickly. I fixed it. But i wonder if it will crack again the plastic line is brittle. But I have more new line and connectors, so ......
     
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  7. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    Very likely will. The older Pete's are having the same issues, but running 20-30 year old stratoflex. You can spray down the supply line to the governor and signal to the dryer with soapy water, and the both lines will be leaking the entire length.

    Whether stratoflex or plastic, I usually replace both with high quality plastic line, and don't use quick connect fittings at any of those connections.
     
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