97 E320 W210 vacuum question

[mcmattaustx]

Hello, I believe I have a vacuum leak. When I accelerate, my AC air volume decreases. I think a flap is closing. The blower seems fine and I have a new alternator.

I was looking at the front of the engine under the front cap and there is a vacuum solenoid with 3 ports and electrical connector. The one pointing downward has no tube in it.

Should it? If so, where does the other end go?

Thanks