I am in the market for a used truck and today while looking over one that I am interested in I noticed something while doing the "brake bleed down" check. There was no warning horn when the light came on.
I remember the first Pete I drove it had the same condition... someone had disconnected the warning horn. Off the top of my head I cannot remember exactly why but I think it has something to with it throwing a false signal/light.
This truck, an '04 the same thing... taking it one step further I also notice one of the warning light is blacked out by what looks like black marker. I think I may know what it is. The trans oil temp gauge is pegged max 300+ with and without having a power supply. I wonder if this it the issue?
Does anyone have any insight to the Peterbilt warning horn system? Or what if any system throws false warnings that need this type of action?
Thanks for reading and your help.
Peterbilt Warning Horn System?
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I don't know what model Peterbilt you're looking at, but on my Peterbilt 379, the low air alarm is a small speaker on the warning light assembly toward the top of the dashboard. If you take off that dashboard panel, the small circuit board containing the speaker will be plainly visible at the very top. It has a small wire (3 pins I think) going to a connector on the same circuit board as the speaker itself.
Hope this helps!
I should have listed the truck and it is a 379 and the old Pete was a 378 and the speaker was in the general location you stated.
That is what I am worrying about.. the horn not going off durning a DOT inspection.
NICE KW I LOVE CABOVERS ALL OF THEM uhhh sorry did i say that out loud... you can pick those buzzers up pretty much anywherethere is a salvage yard i used to go by in fresno area on 99 cant remember where exactly but peterbilt or any parts house will have them so its just re-plug it in. or you could put a pressure switch set for whatever you want it at in the air tank and wire it to any kind of warning device.
(train horn) hehehehehe
Thanks... but I cannot take credit for the KW. It was my friends that he was restoring and in fact he still has a lot of parts just laying around. I told him about this forum and he should be joining soon.
In regards to the horn I will be willing to bet they disconnected it and it works fine. And that there is something else that is the issue.
But if not... thanks for the advice and hopefully it'll be an easy fix.
You don't have to have both.
You have to either a visual or a audible warning
It very specifically says OR, not AND
§393.51 Warning signals, air pressure and vacuum gauges.
(c) Air brakes. A commercial motor vehicle (regardless of the date of manufacture) equipped with service brakes activated by compressed air (air brakes) or a commercial motor vehicle towing a vehicle with service brakes activated by compressed air (air brakes) must be equipped with a pressure gauge and a warning signal. Trucks, truck tractors, and buses manufactured on or after March 1, 1975, must, at a minimum, have a pressure gauge and a warning signal which meets the requirements of FMVSS No. 121 (S5.1.4 for the pressure gauge and S5.1.5 for the warning signal) applicable to the vehicle on the date of manufacture of the vehicle. Power units to which FMVSS No. 571.121 was not applicable on the date of manufacture of the vehicle must be equipped with'
(c)(1) A pressure gauge, visible to a person seated in the normal driving position, which indicates the air pressure (in kilopascals (kPa) or pounds per square inch (psi)) available for braking; and
(c)(2) A warning signal that is audible or visible to a person in the normal driving position and provides a continuous warning to the driver whenever the air pressure in the service reservoir system is at 379 kPa (55 psi) and below, or one-half of the compressor governor cutout pressure, whichever is less.
LoneCowboy thanks for the regulation! This is exactly what I was looking for!
I also found this information....
S5.1.5 Warning signal. A signal, other than a pressure gauge, that gives a continuous warning to a person in the normal driving position when the ignition is in the "on" ("run") position and the air pressure in the service reservoir system is below 60 psi. The signal shall be either visible within the driver's forward field of view, or both audible and visible.
So do I understand this correctly... if we have the gauge and the light then, then the light can be burnt out and the horn and gauge qualifies?
Now I need to figure out what light is blacked out and which will probably lead me to the horn.
Thank you again!Last edited: Oct 24, 2009
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