what is this thing?

[johnnybronco]

It sits on top of the A/C accumulator (I think that's what it's called) by the firewall,it looks like a big, grey suppository and it's got a vacuum line coming off a 3 way running into it. The skinny little vacuum line broke off (after only 22 years!) right at the suppository. I got the line capped but am wondering what this thing does and do I to fix it?

 

[AllanD]

that's the vacuum reservoir for the vacuum actuated blend door in yyour ventilation system.

AD