dash lights don't work wiht headlights?

[boomer baird]

hey listers, My 86 4000q dash lights willnot work when the headlights are
on, It's been driving me crazy enough to drive my other cars. What's the
blatantly obvious problem I am missing. Thanks boomer
79 volvo 245
83 urquattro
84 gtv-6
85 callaway gti
86 4000q
86 5000swagon
94 b4000