My team had the same problem a while ago, but figured it out.
If you take a look at the
table in the manual, you'll see that the am-0912 can NOT be powered by a spike relay. It's got nothing to do with your wiring or your programming, it's simply that it can't be run off of only 20a current.
The table also specifies motors that can be used with the spike, but they're weaker motors, and thus might not be suitable for what you're doing.
Hope that helps.