1972 250 C Vacuum Advance help!

[P2Razz]

Hello Everyone,

I am trying to figure out wether or not my vacuum advance is working properly. I've attached my vacuum gun to both ports while the engine is running and I the retard seems to work, but not the advance. I took the vacuum module off of the distributor and then used the vacuum gun on each port; this time the retard moves and holds, but the advance doesn't. Does this mean it's bad, or they work together and i need both be hooked up?

Thanks for any advice.