parking brake light flashes

[twisted60]

So had some free time and got started on a few projects for the 5 ton, 1st issue was to figure out why the failsafe horn would not stop squawking, I hit the TM's and tried my best to follow directions but coming from a "I don't need directions" background I had a little trouble. First issue I came across was no secondary air pressure switch (see Pic), in it's place was something being used as a plug... So I installed a new pressure switch, checked the wiring and fired up the truck...No change, still sounds like the wife when I come home late...

The parking brake warning light flashes with good air pressure, the Low air pressure warning light goes out right at 65psi and stays out, air pressure in tanks shows between 120 and 140 psi while driving. For now I will disconnect the failsafe module. Looking for wisdom to fix the parking brake issue.

Other project I will post in "what have you done to your 5 ton this week"

Thanks for any and all help.

 

[The HUlk]

When the parking brake is released an electrical switch should apply GND to wire 584/PIN I on the failsafe module causing the flashing parking brake lamp and buzzer to stop. I'm guessing the switch is not connected or working correctly(open circuit).