Broken valve... what is it?

[SMFire History]

Tracking down some air leaks on our 52 LS125 with air brakes and broke a threaded post off the bottom of this valve (old red one) located at the passenger side firewall.

Air line goes to a 8 way air tee. Top wire goes to ground, bottom wire to the harness and then to who knows where.

I don't think it's the brake valve as that's at the frame rail on the drivers side IIRC.

Any suggestions as to what it is? Replacements available?

Thanks,

Dom

[Maddog13407]

looks like an old style low pressure warning buzzer sending unit. they made all sorts of styles of them.

[SMFire History]

Thanks Maddog. I'll take it to my local truck shop with that in mind.

[carlotpilot]

brake light switch?

[fxfymn]

Did you touch the wires together to see if a buzzer sounds? I would also check the switch's continuity to see if it is normally closed or open.

[Vladislav]

Almost as Maddog said, the warning buzzer switch.

The threaded post you've broken might be taken out from the housing together with isolating bushing and swapped out with a similar one.

It too probably the same part is also a contact terminal inside of the valve body and might be fabricated of a common screw. A brass one would work better.

I'm not 100% sure since haven't taken mine apart yet but it seems to me the way I said and worth a try.

[MHfred]

I don't think a 1952 would have a buzzer. It looks like the brake light relay on my 1954 White.

[SMFire History]

Thanks for the tips. Nothing noted when wires are connected but our harness is a rats nest so no telling whether it's connected to anything at the other end. Brakes and brake lights work fine without it installed. I had to fix that once before and it's on the drivers side frame rail.

Still not sure what this is but I'll get a replacement and wire it back up. For now the air line is capped.

I'll reply if I get any good info on it's purpose.

Dom

[j hancock]

Early version of a flux capacitor....?

[b615rich]

Funny. But they didn't have those til 55.

[Vladislav]

They HAD them. At least in 1945.

Buzzer reminder switch.

[41chevy]

They HAD them. At least in 1945.

Buzzer reminder switch.

Military, Emergency and Bus Chassis had them as standard equipment and optional on standard chassis. According to my old time MACK PARTS MAN

[SMFire History]

Anyone have a pic of the buzzer so I know what I'm looking for under the dash?

[Vladislav]

Military, Emergency and Bus Chassis had them as standard equipment and optional on standard chassis. According to my old time MACK PARTS MAN

Paul, that makes sence.

And partly answers the question wich recently roamed in some deep ends of my mind - what military NR and resque 125LS have in common

[Vladislav]

Anyone have a pic of the buzzer so I know what I'm looking for under the dash?

Ufff... I would say track down the wire and find it but you noted the harness is off.

My cab is currently difficult to come along. I might try that in a couple of days.

[SMFire History]

Thanks for the info guys. The truck shop has a replacement but it looks nothing like this old style switch. I held off for now and think I'll pull this apart and see what I can do.

[41chevy]

Paul, that makes sence.

And partly answers the question wich recently roamed in some deep ends of my mind - what military NR and resque 125LS have in common

The original requirement was the U.S. Department of Defense requirement from the mid 1930's. They felt it was needed because the military drivers were not considered "professionals" with little or no driving experience. Easier to say "don't move when the buzzer is buzzing" than teach everybody to wait for air up.

[fxfymn]

Anyone have a pic of the buzzer so I know what I'm looking for under the dash?

Try checking the wire going to the switch for voltage with the ignition on. If it has voltage you can then short the wire to ground to sound the buzzer so you can find it. I assume you have heard a buzzer when you start the truck after it sits and the air pressure has gone down??

The pressure switch should be normally closed until the air pressure rises enough to open it.

[SMFire History]

There is no buzzer audible with low air. There are a lot of small leaks so it bleeds down to zero overnight. I would imagine if it had a buzzer it would have been disconnected because it would always be on when you first got her going.

[Vladislav]

Easier to say "don't move when the buzzer is buzzing" than teach everybody to wait for air up.

That's what exactly needed to me. Good thing when a truck has Maxi's - no run with no brakes.

For the buzzer it works in my 1943 NM. When you switch the key on you can hear it and until the pressure is up enough.

But it doesn't sound as a constant "bzzzz". Just "tsick-tsick-tsick". Like an old on-wall clock but 3 times faster.

[fxfymn]

Do you have plans to re-wire the entire truck? Based on your description I'd say you need to. It would be a shame to bring it this far and then lose it because the wiring caught fire.

Chances are the buzzer just burned out since it would quit sounding right after it built up air. Most older trucks with air brakes regularly leaked down rather quickly, so it wasn't unusual to sit in quarters building up air while everyone else got dressed and ready to ride. When the buzzer quit you knew you were OK to release the maxi-brake without causing the pressure to drop enough to re-activate the maxi. Some places even kept the trucks plugged into the station compressor to ensure they stayed aired up.

[609albert]

All 5 of the apparatus in my dept.have built in compressors on them that we keep plugged in to a land line for air and battery. And my 54 L Ikeep it connected to a Battery Tender (2 plugs wired in to the system)