I have no low beam headlights. already checked bulbs, fuses, relay and dimmer switch. can you help?

If you have already replaced the switch and checked the connections, there could be a few other possible reasons for the low beams not working:

1. Relay issue: The headlight relay controls the low beams. Check if the relay is functioning properly, if not, replace it.
2. Fuse issue: Check if the headlight fuse is blown, if so, replace it.
3. Wiring issue: There may be a problem with the wiring between the switch, relay and lights. Inspect the wiring for any damage, such as frayed wires, loose connections, or melted insulation.
4. Ground problem: Make sure that the ground connection to the headlight is secure.
5. Light bulb problem: Finally, check if the low beam light bulbs themselves are functioning.

If these checks do not solve the problem, it may be necessary to take your truck to a professional mechanic for further diagnosis and repair.

Solution: If both headlights aren't working, it's unlikely that a bulb is at fault. The likely cause is a fuse, headlight relay, headlight switch, dimmer switch or a wiring fault. ... Consult your owner's manual to locate the main fuse for the headlight circuit and replace that fuse with one having the same amp rating.
OR
Most total headlight failures are caused by a bad component like a fuse, relay, or module. Wiring problems can also cause both headlights to stop working. High beam headlights don't work or low beams don't work. The cause: A burned out bulb, or a problem with the high beam switch or relay.
https://www.lifewire.com/fix-non-working-headlights-4137021

as you checked already fuses, relays and bulbs there must be something wrong with the light switch in the dashboard.
- either a loose connector or worn out contacts. first remove the switch and spray some WD-40 or similar contact spray into the connector from behind - if that does not help you have to replace the light switch with a new one...

Just low beams headlamp switch, bulbs, dimmer switch, low beam relay, fuses
just hi beams : dimmer switch, high beam relay, bulbs , fuse
Both Headlamp switch , dimmer switch, fuse, bulbs.

If you have checked and discounted the relay, the only things left are the headlight switch and the wiring and to the headlights. Try the switch first. It is not impossible that both bulb's low beam filaments may have fused at the same time, unlikely but not impossibly. (It will not be fuses, unless two fuses blew together).

Hi Every single time I have had a failure of low beam in a headlight without failure of high beam, it has been because the lamp bulb or halogen lamp module has reached the end of its serviceable life, not because of any wiring problems. Low beam burns out first because it is on the most. If low beam is lost simultaneously in both headlights, I would check fuse first, then the headlight switch. If low beam is lost on one side only, it is almost always going to be due to the bulb or lamp module needing to be replaced. In that case, replace them in both headlights because the other one will be going kaput in short order, as well.Also if you already replaced the fuse and bulb check the headlight dimmer control switch.
Thanks for using Fixya.

The dimmer switch on the stalk usually operates a relay in the fuse box.
It could be the dimmer switch, relay, lowbeam fuse, or odd coincidence both lowbeam filaments went out.
Use a test light and work backwards.

do you have low or high beams?

LOW BEAMS: When headlight switch is turned on the headlight relay is energized providing voltage through fuse 37 and 38 to the headlights and the low beams come on.

HIGH BEAMS : same thing as above thru fuses 37 & 38. When the dimmer is in high, the dimmer relay provides ground to the high beams, and the high beams come on.

1. pull your flash see if lights come on?
2. check fuse 15 if good
3. check fuses 37 & 38.

......No other History, symptoms, clues, things already checked?
Would check the fuses and relay box
Would check the manual (haynes or ?), if separate relay(has contact points that can fail by repeated arc damage like a switch) for high beams, if so could potentially test by switching high relay with low or a test patch wire from battery to the high beam terminal of the relay.
...if not fuses or relays, then potentially the column light/dimmer stalk which is a much bigger pain...
...could also spray some electrical contact cleaner into the column dimmer/light stalk switch and see if any result.
...So, start with the headlights and work back toward the switch---verifying that can get each stage to cause the lights to function by bypassing direct to battery current source.
...hope may have helped

Replace bulbs yet? Dimmer switch may be stuck on high?