Originally Posted by Whale Pilot

If you are in Vnav, set the higher altitude in the MCP then press the altitude intervention switch.

Remember Vnav Spd in climb when you are in the Vnav Climb phase of the Vnav profile. If you get Vnav Alt during the climb, the MCP altitude has captured. Even though you are still climbing, you will have to press the altitude intervention switch again to continue the climb if you are given a higher altitude. The only time you will have Vnav Pth while in the Vnav climb phase is if you have altitude constraints set on the Act Rte 1 Legs page and the MCP altitude set to an altitude higher than the constraint.

Still confused, PM me or give me a call.

Whale