Highbeam headlights work but no low beam, it is not the switch........?

Check fuses first!

This is either the headlight relay or the dimmer switch.

It can be issue with headlight switch,but as its already been replaced.Try disconnecting high beam headlight wiring from headlight assembly and reconnect direct external wire from headlight switch to headlight assembly,then by switch see if headlight is getting off and turning on or not.
See below related help links,similar to your issue.Click the link below:----
Only high beams work but head lights not working on Ford F350?

http://howtobyme.blogspot.com/2011/11/only-high-beams-work-but-head-lights.html

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Only high beams working on GMC Savana?---------- High beams stopped working but headlights still work? http://howtobyme.blogspot.com/2011/11/highbeams-stopped-working-but.html
---------- • Working of Headlight switch? ----------

• Both headlight bulbs blow together? ----------

• Car headlight bulbs don't last long?
------------ Only one head light works on 2001 Dodge Caravan? http://howtobyme.blogspot.com/2011/11/only-one-head-light-works-on-2001-dodge.html

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these will help.
Thanks.

the headlight switch sends power to the highbeam switch which controls both low and high beams, if the bulbs are good i would say it is a faulty high beam switch, if it was the headlight switch the highs would not work either.

If your highbeams work theres a strong possibility that BOTH your headlight bulbs the low beam filament is burned out, if the highbeams dont work either check all related wiring and fuses for the headlights also the headlight switch on your steering column....

AT FUSE TERMINAL #45 TO THE RIGHT OF THE HIGH BEAM RELAY AS YOU ARE LOOKING INTO THE ENGINE COMPARTMENT FROM THE FRONT OF THE VEHICLE. THERE IS A 15 AMP FUSE, PULL IT AND SEE IF IT IS BAD. IF IT IS REPLACE IT. THIS IS THE FUSE FOR THE HIGH BEAM RELAY.

try checking the fuse first highbeam and dipped use different fuses.

it is ur switch that changes it from low beam to high beam
[ turn singnal switch]

Yes there is a relay switch that allows the low to high beam switch to occur. It shoud be mounted under the hood along the firewall. Check your manual too!

Thanks,

Mark

try replacing the fuse because low beam and high beam are two different systems