fordguy2100

Do you have a crewcab?

1Uncle5Jessie0

yes

fordguy2100

That explains the lack of passenger switch.

You're positive your dash airbag light never flashes? But comes on when you go to start?

1Uncle5Jessie0

comes on during the cluster check when i first turn the key then goes out. that was the first thing i checked when i looked up what the beeps meant. Then i fund on another forum someone with same problem that said they changed there headlight switch and it went away, so i put my spare one in and the beeping stopped for a day and then came back.

fordguy2100

I'd try a few things (again ford engineers put that in for a reason, there is something going wrong. Maybe it's the airbag maybe it's something else; not something I'd gamble my life on)

1. Make sure there are no loose wires/connectors under the seat. 2. Replace the dash bulb (I know you said it works but there could be some sort of fault within the bulb triggering the beeping. They are cheap so it's not wasting money to try it) 3. Take it to auto zone and/or ford dealership. I believe airbag codes can still be retrieved from the trucks control module with a scan tool; double check there are no codes stored for the airbag system.
Lastly, in my quick research some people have mentioned bad batteries. Is yours new or old? Have another vehicle you can swap batteries with to test the theory?

1Uncle5Jessie0

i saw a post about weak batteries causing it too, switched batteries with my other 03 f150 same thing. the guy i bought the truck from had it at 2 shops and ive taken it to ford since my land lord works there and no one can figure it out. also ecerything in the interior thats supposed to illuminate when you turn the head lights doesnt work either, both shops and ford couldnt figure that out either.

fordguy2100

So that's probably the fault that's tripping it. You've probably got a pinched or pulled wire somewhere behind the dash. I'd look for a schematic that shows which wire from the headlight switch triggers the dash lighting up.

Also how do you drive at night if you can't see the cluster? I assume by everything that should illuminated you mean the dash and the hvac controls, yes?

Edit* this might be the schematic you need
Edit2* another user found which wire lights up his dash -> https://www.f150forum.com/f6/dash-li...switch-129706/
Edit3* since it worked for a day when you installed the other switch, I wonder if the wire isn't fully seated in the connector and was pushed on when you connected it but under normal use got pulled back out. Against check the wires for continuity and check to make sure you have proper voltage when the switch is turned. You might have a short or pinched wire

1Uncle5Jessie0

the guy i got the truck from hooked up 2 leds in the corners of the cluster wired up to a on/off cigerette lighter switch

1Uncle5Jessie0

i have every wiring diagram for the truck

1Uncle5Jessie0

i never destroyed anything taking the beeper off, just desoldered it so that i can put it back in when the problem is solved. I have 2 complete interior wiring harnesses also ive pulled from other crew cabs.