no buzzer

[m-35tom]

OK, I have spent hours looking for a flow chart to diagnose the air buzzer not working. I cannot find any mention of it in any manuals nor any wiring diagram. There is no power to the switch.
help is needed.
Tom

 

[coachgeo]

OK, I have spent hours looking for a flow chart to diagnose the air buzzer not working. I cannot find any mention of it in any manuals nor any wiring diagram. There is no power to the switch.
help is needed.
Tom

since it is a common item and setup across commercial type trucks with air brakes... try searching out info on a generic truck with air brakes. It is bound to be very similar in wiring.

 

[m-35tom]

sorry, it would be the same as in when the air is low the buzzer comes on, that would be the limit of the similarity!
I need to find the diagnostic flow chart in the LMTV manual and I cannot.

 

[Suprman]

The repair tm should have a troubleshooting flow chart for that.

 

[m-35tom]

and what manual is that? I have them all and can find nothing.

 

[coachgeo]

and what manual is that? I have them all and can find nothing.

here is a breakdown of what each manual is

the numbering of the LMTV 1078 manuals from 1998 is that manuals are all in format of " TM 209-2320-272-##: " the -##: below identify manual type

10......... is Operations manual
xP........ is Parts AND Special Tools (24p for LMTV)
34........ is Maintenance AKA.. laymen's terms- General Service and up keep
20........ is Service/Technical Repair manuals. For us farm tractor guys..... same as FSM's ( Factory Service Manuals )


hint for how TM's in general work:
. Look at the data plate on your equipment. Write down the modal number and NSN. Look at the cover of each TM. Find the proper model number and NSN. That book is for you.
. Then look in the section of the Parts Manual under Usable on code. Find the usable on code for your equipment and write it down.
. When ever looking up parts for your equipment, make sure the Usable on code, (UOC) listed next to the part you are looking up is the same as what you wrote down.

 

[m-35tom]

OK, thanks, I finally found it. It does not help that there IS no low air warning buzzer. It is an audible alarm. And my truck is an A0 which has many different things than an A1. Plus whoever was in charge of the wiring diagram had no clue how to make a readable diagram. I have been an electronics tech for 55 years and most of the military diagrams are crap.
Tom

 

[coachgeo]

...my truck is an A0 which has many different things than an A1....

Only full Tm's for the FMTV trucks are for A0's. A1 manual's are considered as "no release to public" by military

... or did you mean to say your truck is an A1 and manuals are A0?

 

[doghead]

I wonder what it's called in the -10.

Often correct terminology is helpful when diagnosing problems.

 

[doghead]

Sure enough, in less than a minute, I was able to find this In the "desription and use of operators controls and indicators" chapter(on the first page.

18. Audible Alarm.
A steady tone sounds when air pressure is below 65 psi (448
kPa). A wavering (dual tone) sounds when troop transport alarm switch is activated
(on vehicles with troopseat kits). A steady tone sounds when M1079 Van body door
is open.

and, fwiw, I dont have one of these truck, nor am I very familiar with them, or do I have the TMs saved on my computer.

 

[Ronmar]

OK, thanks, I finally found it. It does not help that there IS no low air warning buzzer. It is an audible alarm. And my truck is an A0 which has many different things than an A1. Plus whoever was in charge of the wiring diagram had no clue how to make a readable diagram. I have been an electronics tech for 55 years and most of the military diagrams are crap.
Tom

Yea, that one is worse than most and kinda hard to follow to get an idea of how a circuit functions as it jumps between so many pages. It is also about 30’ long when you print it all out... What I have found though is that the A1 schematic is easier to follow for getting an idea of basic circuit functions.

in this case, power comes from CB77 to feed about half the lights in the indicator/idiot light panel. And the + side of the buzzer. It flows thru its respective lights for front and rear air pressure, past a pair of steering diodes and down to the pressure switches and to ground to complete the circuit when those contacts are closed. One side of the diode pair feeds the buzzer and the other side feeds the “master stop” indicator lights.

In normal operation, the voltage feeds thru the lights past the diodes keeping them biased off and you should see supply voltage at the pressure switches. When the switches close around 65 PSI, current flows, illuminating the bulbs. The voltage drop at the diodes causes current to also be pulled thru the diodes, which cause the buzzer to sound and the master stop light to illuminate. You can see most of this on foldout 12 of 34 in the A0 schematic. PX7 is the connector for the indicator panel. Pin 27 is power in to feed half the lights and pin 16 is this same power out to the buzzer. Pins 13 and 25 go out to the pressure switches and to ground when closed.

So my first question would be does your indicator panel function normally? Mine was inop except for a really dim high beam indicator when I got it home. Nothing else worked, no buzzer And no alternator output. Come to find out a clip on PX7 was broken and the connector was pulled out on one side. When I reseated the connector everything worked and the oil pressure circuit could power the excitation relay via the indicator panel...

 

[Awesomeness]

It's also worth checking to see if the buzzer is actually bad first. I've been in a truck where a soldier hated the sound of it, and jammed his pocket knife in there to damage it. Mine is mostly broke, and only works sporadically.

 

[aleigh]

My buzzer vanished this one time and some of my warning lights on the dash were acting weird. Turns out one of the connectors had pulled loose - the buzzer runs through the panel. Re-seated and all problems solved.

 

[99nouns]

OK, I have spent hours looking for a flow chart to diagnose the air buzzer not working. I cannot find any mention of it in any manuals nor any wiring diagram. There is no power to the switch.
help is needed.
Tom

You know it might be because no one really likes one of those annoying buggers you have to listen for 5 minutes before you can move, I actually learned the habit of walking around the truck checking safety instead of sitting in it listening to that crap...

 

[m-35tom]

buzzer fixed. I had removed the display unit above speedo before I got batteries to make a new lens for it. It has to be there to power the buzzer.

 

[Ronmar]

buzzer fixed. I had removed the display unit above speedo before I got batteries to make a new lens for it. It has to be there to power the buzzer.

Yep...