Tester?
When working with electricity it's handy to keep in mind that if shooting for power with a meter the meter (especially real good meters) will show power but the power can dissappear soon as the circuit is put under load because of a high resistance connection (connection as an example).
As another example, if the 'dimmer' is one click into 'on' (max dim) you'll read system voltage on an open circuit.
What I would do is make sure the circuit is actually getting power at teh cluster plug and that the circuit has ground before working with the cluster itself.
Like Bernie said in another thread, these clusters can be/ are fradgile damned things. Working with one too much could easily turn cluster work into a cluster f**k.