1997 GMC Yukon No Headlights but have daytime headlight lig

Electrical problem
1997 GMC Yukon V8 Four Wheel Drive Automatic

Checked fuses, relay, headlight switch with other good ones varified good from other Yukon, but these made no difference, lights still do not come on but day head lights do shut off when switch is turned to call on Night time headlights. Bulbs look fine and only has single filement in low beam anyway, plus can not get low or high beam to work.

all other lights work fine on parking light setting and all dash lights work fine. Is there anything that is typical with these Yukons or GMC units that I should check before going crazy looking for a disconnected wire?