Low air warning pressure switch

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by B5love08, Mar 4, 2024.

  1. SmallPackage

    SmallPackage Road Train Member

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    Yeah. Its mind boggling how many wires are in that dash. That manifold seems deep down in there because of the rats nest of yellow wires. On my ‘99 I’ve replaced the low air buzzer switch three times over 25 years. Two of them started leaking air at the metal crimp were it connects to the plastic top. Made the first one easy to find.
     
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  3. B5love08

    B5love08 Light Load Member

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    Yea mines an 1999 but vin comes back to a 2000 and I’ve replaced the buzzer so got that back working and the low air warning light used to come on and buzz but stopped a couple months ago and it’s time for a new inspection sticker so looks like I have to go fishing
     
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  4. Big Road Skateboard

    Big Road Skateboard Road Train Member

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    As long as either the light or buzzer works, you don't need both to pass DOT
     
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  5. skallagrime

    skallagrime Road Train Member

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    Yep, i turned my buzzers off on my trucks, nothing more obnoxious after just waking up than 3 minutes of

    ***bbbbbzzzzzzzzzzzzzzzztttt
     
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  6. B5love08

    B5love08 Light Load Member

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    Yea neither are working
     
  7. skallagrime

    skallagrime Road Train Member

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    That pic you sent, with key in on position (but not started), disconnect the wires and then short it with a paperclip or something, check around the cab if nothing changes too obviously doing that.

    Might be worth putting 12v straight t your buzzer/light to make sure they do work and its not a fuse somewhere
     
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  8. Rideandrepair

    Rideandrepair Road Train Member

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    Might be. Both my 99 and 2000 Classics were there, along with the brake switch ( normally open closes at 5 Lbs pressure turns brake lights on.) It’s hard to read them. Ones red ink ones green ink if that helps. If you already have the new one, you’ll see the stamp on it. Since it’s normally closed and opens at 65lbs and shuts the buzzer off. Must be stuck open. Maybe if you unplug it and jump the pigtail it will turn the buzzer on. Then you’ll know .
     
  9. SmallPackage

    SmallPackage Road Train Member

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    The brake light switch may be on the peddle like an old GM car. It is electric only. Both of ours were. You can here it click on and off with key on and engine off. Press peddle with hand and it should be hearable.
    My ‘99 had a recall on it because the clip that held it against the peddle wasn’t strong enough and would cause it to push back and not work lights. Thats when I became a where of that nonsense of a switch on an air brake truck. There are a few things on the Business Class trucks that are not traditional Frieghtliner ways. That series was Mercedes designed and influenced.
     
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  10. B5love08

    B5love08 Light Load Member

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    Brake switch works I hear it clicking
     
  11. B5love08

    B5love08 Light Load Member

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    I pulled apart dash and this is what I found near the green air line I’m hoping this is it?
     

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