1975 headlight doors won't close

Just bought the car on eBay; great shape but this is one of the little problems I need to fix. The headlight doors stay open all the time, and they should be shut except when the lights are on. Seller said vacuum lines need to be replaced; took it to mechanic who said lines are OK, some kind of vacuum switch under the hood needs to be replaced. Manual is no help in identifing exact name of this part, but it's a little metal object connecting some rubber vacuum lines together.

Any help on the name of this part so I can find a replacement is appreciated. If the mechanic is wrong, any other advice on troubleshooting the problem is also appreciated. Thanks,

--Don:screwy: