1995 Freightliner FLD Low Air Warning

im working on getting an old 1995 FLD back on road. Currently I’m stumped on the low air warning system (it’s not working). The original buzzer and light were located in the dash info bar. But that device was damaged and has been removed.

I’ve located the low air sensors, there are two of them behind the steering column. I can verify this because they both have red stripes which indicate the LAW system. But they’re so deep in there I can’t reach them. I’d have to dismantle the steering column to reach these things.

Even if I do reach them, I don’t know how the circuit works. Do these sensors work together to put out one signal? Would it be a 12v or ground signal? Does the signal come on at 60psi?

I’d love to find the wire still existing in the dash, hook it up to a light and be done. it probably still in there. But there’s nothing but 1000 yellow wires in there plus I don’t know if I’m looking for a ground or 12v signal or if it comes on or turns off at the 60psi.

Any help on this would be great.

 

Ok great info. So I should be looking for the signal to shut off at 60 psi. I’ll rip out the carpet and see if I can get in there.

There are some air switches at the parking brake. I tested those but they’re not for the air alarm. Other threads pointed me to the steering column and indeed there are more air switches there, 2 of which have red stripes which supposedly are for the low air.

If I can find the right wires I think I’ll just hook it up to the existing air suspension dump buzzer and add a light. That shouldn’t be too hard with the right wire and signal. Yep oos criteria. I don’t need or want a low air warning system. However it seems to be a top concern at the local scales.

 

I went out and tore out the carpet behind the steering column. By this point I could see 4 air switches. 2 of them are looped together with one going to ground and the the other going up to dash. I was able to trace that one behind the speedometer. This wire does work using a test light. I’m getting a ground signal above 60psi. Which is good news.

But this presents a challenge for my basic wiring skill. I need a ground below 60 psi to activate a light and buzzer.

How to wire such a situation?

 

Oh good, now I understand the purpose of a 5 pin relay. Ill go with that, the truck is full of them I should be able steal one from somewhere.

 

this 5 pin relay works. the light and buzzer work good.