They do have single filament h4 bulbs. Does you h4 bulb have one or 2?
The H4 plug has 3 terminals, ground high beam and low beam.
I'd make sure that the bulbs themselves are actually capable of firing the high beam filament
If these are the rectangular 5x7 6054 Hella sealed beam replacements, it is said that once the low beam is adjusted properly, the high beam is up in the tree tops and ineffective.
Cibie200MM With Phillips extreme h4 bulbs are what I desire, but firmly in the want side of the need/want list.
I am using GE nighthawk 6054 as they are the best sealed beam in this size format. And They get within 0.3v of alternator voltage by bypassing the headlamp switch and using relays instead. That alone was good for an estimated 30% brightness increase.