HELP!! PCM/ Compressor Sticky Fault


Our team is having a serious issue. This close to the end of build season! My oh my!

We are encountering a sticky fault within the PCM. We have switched PCMS, compressors, and wiring. Yet the fault persists and the compressor will not turn on. We have no voltage to the compressor. When we hotwire the compressor, the compressor works fine. We have tried clearing the sticky fault by rapidly clicking the absolutely stupid button, as well as by forcing it to clear within the code. Does anyone have any thoughts or other things to try?

Thanks, and good luck teams! Love, 4593

Are you sure the fault is with the compressor and not with a solenoid? Do you have a picture of your setup that we can look at?

The first thing I would do is unplug the switch, compressor, and solenoids. Then clear the fault and run your code. Assuming the fault does not come back in that test…

Next add one thing back in. Just one. I would start with the pressure switch. Turn the robot back on and run your code. Does the fault return? Manually short and un-short the pressure switch during this test, to simulate reaching pressure and dropping pressure. If the fault has not yet returned…

Add another thing. This time, make it the compressor. Turn the robot back on and run your code. Does the fault return? Does the compressor run as expected? Once the tanks are full and it shuts off, manually release some air until the compressor comes on again, make sure that process is working. Still no fault?

Add the solenoids in one at a time. With each one, turn the robot back on and run your code. Did you get the fault? Actuate that solenoid several times to make sure it works properly.

Eventually, you’ll get the fault again. Whatever you plugged into the system immediately prior to getting the fault is going to be the cause of your problem! Look for shorted wires, obvious damage to the devices, and voltage ratings of your devices (24V versus 12V solenoids). Look especially closely around the terminals on the PCM - it’s very easy to have one or more strands of wire stick stick out and get shorted against a neighboring wire, if you are using a larger gauge or trim the insulation improperly.

Thanks for your help, we got it figured out. After 2 hours of troubleshooting, we found an intermittent bad crimp between the connections.