Air System Diagram for M923A1

[KaiserM109]

Before you RTFM me, I have gone through them looking for the diagram for the air system and didn't find it. After hours in a hot storage yard, I'm just hoping someone can short-cut the search.

I'm trouble shooting my non-working air horn. It seems to have everything wrong with it, I think because it has been hacked by a lousy mechanic. The horn button doesn't work, but I'll get that figured out. Some of the wiring has been messed up by a wild pair of side cutters; I can fix that too. The solenoid is dead, but I hope I can find one on this site.

The problem I need the air diagram to solve is that there is no air pressure to the solenoid. There must be some sort of other valve or solenoid shutting it off. There is something on the fire wall with a couple of hoses going through the fire wall and under the dash and I lost track if it there.

The bare horns work, as my wife will attest. I tested them with my shop compressor while my wife was working at her computer. I don't remember her using that kind of language in our 40+ years of marriage. The fact that I was right behind her shouldn't really make a difference.

If you can help me with the air problem, I'd appreciate it.

Arlyn

 

[cwc]

From the P2P program...the air horn supply comes from the pressure protection valve, should be common with the supply to the wipers...

 

[juanprado]

horn hooks up directly to the air governor. Nothing goes into the dash for the horn. Only air lines in the dash are for the 2 air pressure gauges and the spring brake valve or on the far left for the front axle engage,wipers and air filter monitor.

Common problems are the diodes in the wiring harness next to the horns and the junction box at the base of the column.

 

[cwc]

The P2P program shows the air horn supply coming from the pressure protection valve, should be common with the supply to the wipers...

View attachment 508901

 

[wheelspinner]

For future reference, the air charts are in the rear of TM 9-2320-272-23-5. Them along with all other pertinent charts are listed as foldouts.

 

[73m819]

The P2P program shows the air horn supply coming from the pressure protection valve, should be common with the supply to the wipers...

View attachment 508901

I looked for this, exactly where, like what page or sign post, or more then a hint where the air diagram can BE FOUND.

Never mind, my answer was posted as I was asking the question, now that is a FAST response.

 

[KaiserM109]

horn hooks up directly to the air governor. Nothing goes into the dash for the horn. Only air lines in the dash are for the 2 air pressure gauges and the spring brake valve or on the far left for the front axle engage,wipers and air filter monitor.

Common problems are the diodes in the wiring harness next to the horns and the junction box at the base of the column.

I'll take a look at the TM Wheelspinner referenced to confirm it, but there has to be something somewhere because I unhooked the line going to the horn (with the engine off and the air pumped up) and expected a rush of air, but there was none. I checked the gauges and they were still showing pressure.

I'm familiar with clamping diodes (I do electrical design) and that was one of the first things I checked. The coil in the solenoid has no continuity, even in the mega-ohm range, so that is one contributing problem.

This truck must have been deployed because NO stateside motor pool Sgt. would have allowed the kind of work I'm finding on this truck, misaligned doors, wrong bolts, vinyl tape on electrical wires, ground wire splices with no solder or tape, etc. It's the kinda' crap I used to see in the field when the support facility didn't have parts and the mechanics weren't trained as mechanics. The box at the bottom of the steering column was missing and the wires were vinyl taped so they wouldn't short. Other things, like green over tan over green paint, tell me that it has a history.

 

[Recovry4x4]

FWIW, on most MVs you will find the air diagrams and electrical schematics in the unit maintenance manuals (-20 etc) in the appendix. To leaf through the manual looking for it will be a waste of time. Also to note, on most paper manuals they are nice fold outs that are easily copied in a larger format and laminated for shop and dry erase use.