Just some fundamentals:
The upper sealed beams have 2 filaments (60/40 watt) while the lower S/B's have only one filament (50 watt).
When low beams are selected, only the 40 watt filament in the upper S/B is energized. Looks like this:
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When the high beams are selected, power is supplied to the 60 watt filament in the upper S/B (the 40 watt filament is de-energized) and the single (50 watt) filament in the lower S/B's. Looks like this:
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The upper S/B's have a 3 prong plug. The lower S/B's have a 2 prong plug.
Low beam power is supplied only to the upper S/B's on the tan wire. High beam power is supplied to both S/B's on the light green wires. The sockets and plugs for the upper (dual wattage) S/B's pin out like this:
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The lower S/B's are similar, but they just have the 2 prongs and plugs.
Ignore the blue/white & blue/red wire color codes in the image above. Substitute light green for the Bl/W and sub tan for the Bl/R.
In addition to the Lt Grn & Tan leads, each lamp gets a black ground wire.
When the light switch on the dash is pulled all the way out a common power supply for both highs and lows is sent to the dimmer switch. It is the yellow wire indicated below:
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Power out of the dimmer switch is either on the Lt. Grn or Tan wire.
The fact that you have power to the high beams would indicate that your headlight switch (the push/pull one on the dash) is good.
The problem then, would either be a bad dimmer switch or a break in the common section of the Tan wire (I say the common section because both low beams are non-functional).
Not a bad ground connection because the highs require a ground as well and they are working.
Any chance the sealed beams are installed in the wrong bays (i.e. the uppers in the lower bays and vice-versa)?
Or maybe the wiring plug connectors got reversed (the 2 prong sockets on the three prong plugs and the 3's on the 2's)?
