Compressor Not Shutting Off

Hello, we have been having a issue with both our competition and practice bot where our compressor will not turn off and shoots out the relief valve after 125psi. We already changed out multiple pressure switches but it doesn’t seem to be changing.

Maybe a recent update or something effected this? Does anyone have any advice? Also there is no polarity on the pressure switch and the pcm pressure switch slot right?

There is no polarity.

I’d be looking at your robot code…

Also there is no polarity on the pressure switch and the pcm pressure switch slot right?

No polarity, it is just a switch. The switch must be CLOSED (current can flow) in order for the compressor to run. The switch is supposed to OPEN (current cannot flow) when the pressure reach around 100 PSI. You can verify this with a multimeter IF THE SWITCH IS DISCONNECTED FROM THE PCM.

I suggest you try with no switch connected. The compressor should not turn on. If is does, the PCM is probably faulty.

You can use the CTRE Phoenix Tuner to connect to the RoboRIO and look at the PCM self test in the Phoenix tuner for diagnostic. It will show the state of the switch and of the compressor.

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The compressor control logic is entirely performed in the PCM, so robot code is not at play here.


I had a team at GNR today with this exact condition. We did this exact test, then got them a replacement PCM. They hooked it up and everything worked perfectly.


Thanks we will try this!

Please post photos showing your complete pneumatic system as well as the wiring for the pressure switch and PCM. Check your system against the drawing on page 18 of this document or against the document linked in the first post of this CD thread.

Last year, I inspected a team at CPR that had similar symptoms. Instead of the activating the relief valve at 125 psi, they were blowing up the tubing at 140 psi. I found they had the pressure switch installed after the pressure regulator.

We seem to have found the issue. For some reason after replacing a leaky solenoid and reconnecting the wires all is working.


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