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SESK: Stuff Everyone Should Know · sesk.info/cdl-compressor-governor-cut-out

What does the air compressor governor do when tank pressure reaches cut-out?

It stops the compressor from pumping, at around 125 psi.

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  1. Starts the compressor pumping air
  2. Stops the compressor from pumping air ✔
  3. Opens the air tank drain valves

Why: The governor controls when the compressor pumps air into the tanks. At the cut-out level, around 125 psi, it stops the compressor from pumping.

Huh, didn't know that: For the CDL skills test you build air to governor cut-out, usually around 120 to 140 psi.

The dad joke
Why did the air compressor take a break? It was feeling a little pumped out.
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References

Answer: Stops the compressor from pumping air. The governor controls when the compressor pumps air into the tanks. At the cut-out level, around 125 psi, it stops the compressor from pumping.

  1. California Commercial Driver Handbook (DMV) www.dmv.ca.gov/portal/file/california-commercial-driver-handbook-pdf
    When air tank pressure rises to the "cut-out" level (around 125 pounds psi), the governor stops the compressor from pumping air.
    Checked 2026-10-10.

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