What is this red light for?

Disbus

Senior Member
Joined
Jan 16, 2017
Posts
161
I have this unmarked red light on my dash. It flickers sometimes. Never stays on. All other gauges show normal like temperature, oil pressure, water levels, ......??

Viscosity warning light?

2003 Cummins 5.9 TC2000 FE

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It all sort of depends upon from which circuit that light gets power and ground. The two switches above the light might have something to do with the light. I can't read what the two switches activate.


Most of the time a red tell tale light like that is an additional warning for low oil or low air pressure, or for high engine or transmission temperatures.


Since it isn't right next to an amber/yellow tell tale light I doubt it has anything to do with the overhead 8-way overhead flashing lights.


It could also be tell tale light for the emergency door/exit/window open buzzer.


It could also be a tell tale light to let you know you have left a compartment door open.


The only way to find out for sure is find out what causes the light to light up.
 
Air leaking from this. Mounted behind the rear axle.

Is it a relay valve? ABS Modulator?

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That's a solenoid valve for something, the wires power up an electric coil. Follow the hoses and see where it goes/what it controls.
 
It is an air regulator solenoid....for air operated accessories. Mine is leaking air. Replacement part is ordered.

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Replacement

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It most likely the low air warning light. Please don't remove it. It warns you visually that you are out of air for your brake system. Download a copy of the CDL drivers handbook. Read the section on air brakes. You don't need a CDL but it sure doesn't hurt knowing what is in the basic knowledge requirements.
 
It most likely the low air warning light. Please don't remove it. It warns you visually that you are out of air for your brake system. Download a copy of the CDL drivers handbook. Read the section on air brakes. You don't need a CDL but it sure doesn't hurt knowing what is in the basic knowledge requirements.

Yes, have done so. I drove a semi back in the day but I did refresh my memory. I expect when I replace the solenoid for the auxiliary air control device the red will go away. However I want to note that when the light is flickering and I look at the gauges they are all the way up to max air pressure so I don't know how related that is
 
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Yeah, maybe it's for something else. Back door warning light? It could only be so many things.

One opinion by a diesel mechanic in Georgia says it measures exhaust gas for emissions. Installed by Atlanta School District. Unconfirmed.

This weekend i will be able to trace the wires and see where they go.
 
I’ve got two similar red lights on my dash one is labeled fuel pressure the other is labeled exhaust pressure.

Yes. I think it is the exhaust pressure or how dirty the exhaust is. Some kind of monitor of emissions.

I'd like to shorten the exhaust pipe. I could easily take 10 feet off if i turned it out the side further to the front. Maybe just in front of the rear tires.
 
Mine exits directly in front of the drivers side rear tire. I like it there a lot. It’s not in the way of anything I want to put in the back
 
Mine exits directly in front of the drivers side rear tire. I like it there a lot. It’s not in the way of anything I want to put in the back

Yes. I have a set of mudflaps to install but the exhaust is in the way on the driver's side. In front of the rear tire would be my choice too. I might even be able to hear the exhaust note.
 
Yes. I think it is the exhaust pressure or how dirty the exhaust is. Some kind of monitor of emissions.

I'd like to shorten the exhaust pipe. I could easily take 10 feet off if i turned it out the side further to the front. Maybe just in front of the rear tires.

What's the legality of running the exhaust to the side instead of all the way to the back? I had to repair the part of my exhaust that goes up and over the rear axle with a section of flex pipe that won't last forever. It would be nice to know when it goes I could just junk the rear part entirely and exhaust to the side in front of the rear wheel, as you're suggesting.
 

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