Bought 99 T2000, issues with air buzzer and lights

Today i worked on left tank drain valve since it was leaking. Didnt see any sensors
Tomorrow i have to finish replacing mudflaps and RH tank drain valve and than ill start working on these sensors behind radio
Not much time on weekend between runs. Im glad Volvo is still running strong

 

Well it was sensor on right side manifold. Foward tank. Got new one. Whats crazy if i disconnect black wire from bad sensor buzzer will stop. So in feature you can mKe buzzer stop till you vet new sensor.
In same time i replaced all 3 manifolds and trailer valve since they were leaking. Aloso both pass thru manifolds on firewall were leaking. This truck had a lot of air leaks. I dont know if it was from sitting alot in last 19 years