If we have a off board compressor… Do we have to have the Spike on the robot…or can it be off board with the compressor. I know that the compressor has to be powered and controlled by the robot. ::rtm:: 
R80 doesn’t say the Relay can be off of the robot, it just says the compressor can. (Relays don’t weigh that much, so don’t know what you expect to gain.)
I am not the GDC. Ask on Q&A if you want an official answer.
We just have very little space… and adding a spike will make our board more cluttered.
The only official answer is the Q&A, but I would point you to R85 and R86:
R85. If the compressor is not included on the ROBOT (under the provisions of Rule R79), the “Working” Pressure Regulator, ”Stored” Pressure Gauge, and pressure switch may be located on-board (Figure 4- 16) or off-board (Figure 4-17) (but must be together), provided all other pneumatic rules are satisfied.
R86. If the regulator is kept off-board the ROBOT with the compressor, then only low-pressure (60 psi or less) “working” air can be stored on the ROBOT. The “working” pressure gauge must be installed on-board the ROBOT at all times (Figure 4-17).
Personally, I think that very clearly states which components can be located off-board, and that does not include the spike. From a safety standpoint, I personally would want to see the spike included on board, so you don’t have a pair of live wires dangling off the robot where they could potentially short out and pop the breaker on your PD repeatedly during a match.
That particular safety issue could be mitigated by setting using a quick disconnect similar to what’s used for the battery. You could even route a PWM extension cable along with the power and hot glue it to the outside of the connector.
Regardless, I don’t believe it is legal within the confines of FRC to have an off-board relay to go along with your compressor.
Is there any official rule about having a spike off robot for the compressor?
As pointed out, no rule exists either way, but the general trend of other “offboard compressor” rules is that the Spike has to be on the robot.
If you want to be certain, please ask Q&A for the official answer. Your inspectors will thank you for doing so. “I read on Chief Delphi” is not a reason your robot should be legal. On the other hand, “Q&A says thus-and-so and our robot matches the Q&A, and here’s the Q&A in print” has a pretty high likelihood of getting you past inspection with no problem if your robot actually does match.
We need help with our compressor. They coding is correct and the wiring is correct but the compressor won’t turn on. Any suggestions?
Please and thank you.
Can you post a wiring diagram for your compressor and the code you’re using? It is nearly impossible for us to troubleshoot without this info. Thanks!
Did you turn your robot on? jk check if you put the spike pwn cable in the right slot and if you have a multi-meter check if your spike is getting power, and if power is going to the compresor.