Brake lights staying on

[Gunny65]

1979 Mach Dump Truck, DM685SX. Air brake system. The brake lights are staying on all the time. Even when the truck is not running and the key is off.  I can only shut it off by turning the battery power disconnect switch off. I replaced the air pressure sensor switch as the old one was rusty and one wire was disconnected. That didn't help. I have ordered a manual but it won't be in for a few more days. Suggestions on what to do next?

The low pressure air light never goes off even when the system is fully charged.  The low air alarm does not go off either, which I don't mind. I am not sure if these problems have anything to do with the brake lights staying on at all times.

Edited May 3 by Gunny65

[Gunny65]

2 hours ago, JoeH said:

1980 dm686sx

Low air buzzer is one of these 2^^

I think this one is Service brake lights^^^

T'd into the parking brake knob there's the parking brake light switch.^^^

Wow, I don't have any of that in the glove box.  Mine is totally empty. There is a fuse block under the box but there are no blue boxes anywhere over there.  I looked under the drivers side dash for boxes as well but found nothing obvious.

I am replacing both of the switches behind the brake pedal.  The one you are pointing at and the one to the left of it.  The one on the left is the one that shuts off my low air light. The one on the right, you are pointing at, is a 70psi switch. It did not do anything when I disconnected it.

I looked inside the dash by all three air knobs (emergency, park, and trailer/system).  I do not see a button type switch anywhere in there except on the emergency knob. 

Thank you for the pics.  I am done for today but I will pick it back up tomorrow.  I noticed my blinkers are not working.  Joy.....

[JoeH]

Emergency knob is probably the right spot for the switch.  It should kick the lights on in an emergency braking event. Your truck was set up for a trailer so you have 2 or 3 knobs, whereas mine had always been a straight truck til we slapped a 5th wheel on it as a yard truck for retirement.

We ripped the lift axle out from under the truck and repurposed the "down" switch through a tractor protection valve to run the trailer airlines.

Edited May 10 by JoeH

[mechohaulic]

3 hours ago, JoeH said:

1980 dm686sx

Low air buzzer is one of these 2^^

I think this one is Service brake lights^^^

T'd into the parking brake knob there's the parking brake light switch.^^^

I forgot all about those updated buzzers!! along with a lot more. older buzzers were mounted above clutch pedal on dash frame work. rectangular 1x2 black metal box with( 2 ) TWO wires attached. picture one Gunny65 posted of new valve would/should be brake light switch . picture two of gunny and  Joe H should be the low air sender. which is what I tried to describe earlier as the single pole  3/4X 1 white sender. from what is described in terms of the hacked wiring on this unit ;it will be a long tedious project. 

[Joey Mack]

Mech,  thats where I remember the buzzer to be.  on the back of the triangular gusset above the clutch pedal..  I do know that in the 90's RD models and newer that I have worked on, it's name was changed to a Multi Buzzer.. it was so loud when using turn signals, that all of the drivers in my fleet would un-plug them.. then I would plug them back in when they were in my shop for the next PM.. The DOT Man doesnt like it when they are un-plugged..  

[mechohaulic]

6 hours ago, Gunny65 said:

There are no switches, that I can see, that are directly connected to the main parking system push knob. I took the dash apart and can see in there.  There is a threaded opening on the back of the knob assembly with nothing in it.  No leaking though.  There does looks to be a pressure type switch on the emergency brake knob.  For now, these pics show what is connected to the low pressure switch.  I can not find the low pressure buzzer. The manual I got is not very helpful. It shows a low pressure switch but I see nothing that resembles that switch.  The book pic has an electrical connector on each end. Everything I see has connections on one side. I just don't know what I am looking at. Anyway, pics.

The first pic is of the switch I replaced. It is directly under the brake pedal and connected to the brake valve assembly.  That assembly is on the outside of the firewall.

The second pic shows a switch on the left that has a wire that connects to the switch on the right and that switch wire goes to the low pressure lamp. The other wire connected to the right switch it goes into the wiring loom. Both of those assemblies are directly behind the brake pedal and mounted on the inside of the firewall.

the switch on the left which has the spade terminal unplugged and a possible wire hanging looks more  to be a sender from a kysor AC/ shutter system. I'd plug it on terminal see if any thing happens. red line covering clear picture; but seems to be a wire was spliced into white sender .my first place of tracing  why/ where they go.

[Gunny65]

5 hours ago, mechohaulic said:

I forgot all about those updated buzzers!! along with a lot more. older buzzers were mounted above clutch pedal on dash frame work. rectangular 1x2 black metal box with( 2 ) TWO wires attached. picture one Gunny65 posted of new valve would/should be brake light switch . picture two of gunny and  Joe H should be the low air sender. which is what I tried to describe earlier as the single pole  3/4X 1 white sender. from what is described in terms of the hacked wiring on this unit ;it will be a long tedious project. 

THAT!!  I have a black box right where you are talking about.  It is not connected to anything and I didn't know what it was. Excellent.  Thank you. I will take a pic tomorrow.  There are not any unconnected wires hanging near the box that I remember seeing but then again, I wasn't fixated on that part.

I switched the wires on the new valve I posted a picture of and now the brake lights are not on constantly...however...they do not come on when the brake pedal is pushed, nor at any other time (IE: air pressure at zero, or at full, with parking on or off).  The bulbs come on when the running light switch is flipped. At normal brightness now but I just couldn't get the brake lights working, yet. 

Yep, I expect it to take me a while to figure out the wiring.  Lots of wires not connected to anything and lots of wires that are newer that run to headlights, spliced to old wiring, etc.  The marker lights do not work. The turn signals do not work (I put in a new flasher unit, no luck there).  Right now I just need brake lights and turn signals.  I can work the other stuff over time.

[Gunny65]

5 hours ago, mechohaulic said:

the switch on the left which has the spade terminal unplugged and a possible wire hanging looks more  to be a sender from a kysor AC/ shutter system. I'd plug it on terminal see if any thing happens. red line covering clear picture; but seems to be a wire was spliced into white sender .my first place of tracing  why/ where they go.

I unplugged that switch you saw on the left of my pic.  When I did, the low pressure light turned off. I plugged it back in it came back on.  I then unplugged the white square looking switch on the right of my picture and the low pressure light came on.  I did notice the square switch on the right has 70psi written on it. The switch on the left has no markings at all and looks to be original. Rusty and beat up really.  Now that I know where the buzzer is, I am going to see if that has something to do with the buzzer. I am getting closer.  Thanks everyone.

[Gunny65]

6 hours ago, JoeH said:

Emergency knob is probably the right spot for the switch.  It should kick the lights on in an emergency braking event. Your truck was set up for a trailer so you have 2 or 3 knobs, whereas mine had always been a straight truck til we slapped a 5th wheel on it as a yard truck for retirement.

We ripped the lift axle out from under the truck and repurposed the "down" switch through a tractor protection valve to run the trailer airlines.

Yep, I have three knobs.  Emergency, tractor parking, and system parking. I think the system parking is if a trailer is attached. It also has a jake brake (trolly brake, Johnson bar) on the steering wheel post. 

[Gunny65]

6 hours ago, JoeH said:

Emergency knob is probably the right spot for the switch.  It should kick the lights on in an emergency braking event. Your truck was set up for a trailer so you have 2 or 3 knobs, whereas mine had always been a straight truck til we slapped a 5th wheel on it as a yard truck for retirement.

We ripped the lift axle out from under the truck and repurposed the "down" switch through a tractor protection valve to run the trailer airlines.

I haven't decided what I am going to do with the railroad wheel axles and associated parts.  It is a lot of weight but it isn't in my way either. I would like to take it all off at some point. Maybe repurpose the hydraulic cylinders and valves. I also will more than likely never use the turn table for dumping as it would be way off balance and I have no track to hook the stabilizers onto.  It would be a bit dangerous I would think.  It is cool and all but I really bought the truck simply because it was $1,600 bucks, it ran and it dumped.  I put a clutch in it and some work on the electrical and I have an inexpensive dump truck.

 

 

 

[Gunny65]

This on the passenger side of the engine down on the lower end and back of the engine.  The rope goes into the cab.  I assume to pull on. Anyone know what this is and why anyone would put a rope on it?

 

[Gunny65]

Here is what i think is the buzzer box. One of the spades is busted off and there are no wires close to it that have spade connectors. Another shrug.

[Gunny65]

I have ordered replacement switches.  They will be in next week.

[Joey Mack]

yes to buzzer box, the rope is a home made hand throttle. the other linkage to the rear a bit is the real secondary hand throttle..  ditch the  rope.. do you still have the 'T' handle in the dash below the speedo? 

[Gunny65]

2 hours ago, Joey Mack said:

yes to buzzer box, the rope is a home made hand throttle. the other linkage to the rear a bit is the real secondary hand throttle..  ditch the  rope.. do you still have the 'T' handle in the dash below the speedo? 

The hand throttle is missing.  I found the cable sheath under the dash and followed it to the linkage under the cab.  The throttle handle, dash mount and cable are all missing. At least I know what it is now. Thank you.

[Joey Mack]

👍

[mechohaulic]

rope for throttle cable ???? OH BOY ;  guess better then dead idle . kinda makes a person want to see this unit up close or at least lots of pictures.

[mechohaulic]

On 5/10/2024 at 2:41 AM, Gunny65 said:

Yep, I have three knobs.  Emergency, tractor parking, and system parking. I think the system parking is if a trailer is attached. It also has a jake brake (trolly brake, Johnson bar) on the steering wheel post. 

possibly three brake knobs are yellow (truck parking brakes)= blue center (master control for all brakes ); pulling blue out should set yellow and red . red  right side controls trailer brake systems.  bobtail yellow in -red out type situation.  of course based on the rope throttle = don't guarantee any knob colors . 

[Gunny65]

On 5/12/2024 at 9:04 AM, mechohaulic said:

rope for throttle cable ???? OH BOY ;  guess better then dead idle . kinda makes a person want to see this unit up close or at least lots of pictures.

I imagine the PO used the rope going through the engine cover as a way to set the basic start up idle where he wanted it.  I don't see any other on demand use for it as you can't let loose of the rope and hope it goes back to the starting point since it is pinched as it comes into the cab.  I ordered a replacement idle/throttle cable. All the other linkage is there I just may need to clean it up and lube it.

Edited May 14 by Gunny65

[Gunny65]

On 5/12/2024 at 9:09 AM, mechohaulic said:

possibly three brake knobs are yellow (truck parking brakes)= blue center (master control for all brakes ); pulling blue out should set yellow and red . red  right side controls trailer brake systems.  bobtail yellow in -red out type situation.  of course based on the rope throttle = don't guarantee any knob colors . 

Yep, I think that is accurate. My color order is the opposite (in actual order) but that sounds correct.  I am not towing anything though.  The Red is always off/out.  If I hit red it sets the other two to off/out. The yellow is on/in for normal operation and the blue doesn't do anything if I push it.  While it has the Knob, I think they replaced the trailer lines when they put in the hydraulics and mechanisms for the rail road wheels/axle/etc. I need to look closer but I don't see any glad hands anywhere. There are old stowing spots for the hands but no actual plumbed lines.

Edited May 14 by Gunny65