Bought 99 T2000, issues with air buzzer and lights

I just bought 99 T2000 with 567k miles. 3406E with 13 speed. 260 WB
Thanks to ELD this truck will replace my trusty 04 Volvo with ISX with 1.9m miles
Anyway. T2000 is in good condition for 99. Truck used to pull DSR race cars
I found a few issues. Two of them low air pressure on front tank even pressure is fine. Problem started when i went to Speedco to do DOT inspection. I was holding brakes for inspector guy. After that when i started truck buzzer come on

Also visor clearance lights doesnt light up with headlight switch. But there is another switch on dashboard in the middle on top and with that switch just those visor lights with come on but not with headlights. Tbey will stay on even with truck off

Anyone have any ideas where to start

I know for low air pressure buzzer i should look for bad low air pressure sensor
Thanks

 

The lighting has probably been rewired so driver could leave lights on at truck stop without headlights or truck running.

 

Clearance lights - the 2nd switch from left, is independent of the headlights. At least that was how my 2001 was wired.

Is your low pressure buzzer locked on even with good pressure? If your low pressure switch is still ok, then . . ,

Buzzer is integral in circuit board on back of instrument cluster. You need to poke a hole in it (destroy) and then wire in a couple of cheap buzzers at the dash valves.

Or find a used cluster - with a working buzzer and similar mileage - or attempt to get that buzzer out of the board . . .

 

It could be a bad foot brake valve causing your low air pressure warning when the brakes are applied.

 

I talked with my brother in law and he say its same thing on his 03 387 and 379. Both switches must be turn on together. On my 04 Volvo there was just one switch for all lights

 

My '99 W900 has 4 switches for lights. But it has a lot of lights. I'm sure it's done that way so as to not overload one circuit.

 

Air pressure is good in bith tanks. But little light on front tank gaude is on and its buzzing

I didnt have chance to work on this issue yet, had to do some troubke shooting on reverse light.
BTW where are those low air pressure located. I think its on pass thru somewhere right ?

 

I found where thkse sensors are located. They right begind radio. There is 2 sensor next to each other but there is one more sensor on top. This one is threaded in some kinda block with hoses attached. Thjs sensor have bromen wire. I will hae to take whole thing apart to gain more access and see if this is the problem

 

Those horrid little blue connectors tell me someone has been in there in the past. All your little white tags look in good order, makes things a little easier.

Let us know how you get on.

 

I tryed connect broken wire, same thing. Ill have to start swaping sensors. I got two on bottom and one on top