[ArzaanK]

Is some other part of your code trying to control Relay 3 at the same time?

No, nothing else on our robot is trying to control relay 3 at the same time.

I'd say that it's probably some slip of the mind of your electrical guy (I have many.) Just make sure that 1. Your cable is connected to relay three counting up from 1 (parallax makes it hard to be sure) 2. Your signal is in the correct direction (check with a voltmeter) 3. Your cable has continuity for each of the respective pins (check with an ohmmeter or with a known good PWM cable) 4. Your cable is wired correctly, make sure the connector isn't flipped (simple mistake but easy fix.)

Everything you have mentioned has already been tested. We've tried adjusting pretty much everything electrically.