When the engine is running at idle and I press the button, the engine races (as it should per test process). When I'm driving and I press it, the car will continually accelerate until I let go, but it won't hold speed.
The light never comes on. However, to test this you are supposed to disconnect the cruise harness to the Speedo, then do the idle test. Correct response is no idle up, but the light comes on (which it does). If this is the case, you are supposed to "remove Speedo and have repaired".
The Speedo is supposed to send a pulse thru the Speedo cruise harness. I'm guessing this isn't happening....