help on a 78 headlight problem

when I cut the headlites on one comes up about a inch and then goes back down..I know the vacuum holds it down.. every so often it works OK but then.. fails to come up.. where should I look first..many thanks..

when I cut the headlites on one comes up about a inch and then goes back down..I know the vacuum holds it down.. every so often it works OK but then.. fails to come up.. where should I look first..many thanks..

use a vaccuum gage (mityvac brand) and check for vacuum leaks, you may have to rebuild the actuators.