98 379 oil and air buzzer staying on with key off

Whats up guys . Looking for some help with an issue my dad is having in his 98 379. He came out one morning to the low oil n air buzzers going off without the key in. He was able to turn the blower motor on for heat also without putting the key in or on acc and it sound like a static speaker but it did work. He recently changed the actual key switch so he changed it again with no luck. He open the R/S dash to change a couple air lines and with pushing some wires around it had stopped for a couple days then started back up. He changed the ignition relay then nothing worked on the dash at all but he was able to jump the relay at start the truck so he put the old one back in.With the old relay in and the buzzers going off if he taps the relay it goes off but slowly comes back on like it has a weak spring inside or its getting power from somewhere. Im going down to see him tomorrow and I will get a better idea of whats going on and some pics .

Has anyone had anything like this before? Ive seen a few posts about the air psi on the floor , which was recently changed also, and a few other mentions of possible loose ground wires. Just thought I would post something up to see if I get an response before I get down there.

Thanks in advance.

 

Thanks for the info ! ill check it out later today and let you know how it went.

 

$100 is still cheaper then a tow to a repair facility , which you know will happen on a holiday weekend...

 

Heres a couple pics of the relay changed. The second box mentioned was changed last year.

With the old relay in , when the truck is shut off with key out the warning buzzers stay on ,tap the relay and they shut off. Replace the relay and the truck starts fine but then there is no dash at all. No buzzers or gauges, backlights for the dash but if that new relay is jumped big post to big post all the dash comes back on and works fine.

With the old relay in and check the power with a test light one side is constant hot , as should be, and the other side slowly gets brighter until full bright with the key off which then causes the buzzers to come on.

 

Changed both and it still does the same thing.

 

Soooo.....Figured out what was going on. After looking at the truck and seeing what was happening it didn't make sense. With the old relay in place everything worked fine with the dash . Turn the key off and pull it out and the buzzer(s) would stay on . Had power going everywhere it should as if the key was on. Put the new relay in , that my dad pick up directly from "Peterbilt parts dept" and the truck would start but dash would not come on unless you jump the 2 big posts on the relay. I found it odd as if the relay wasn't getting the signal to close. I looked at the old relay and noticed it has 2 posts on the closing side and the one the dealer had given him was only 1. He had given them the VIN and they swore up n down it was correct. Original p/n was Bosch 0 332 002 150 , New from the dealer we were given Bosch 0 332 002 156.

Moral of the story , ensure the part numbers are correct even from the dealer. If its a superseded # find out why it was updated.Parts can physically look the same but internals completely different.

Thanks for all the help .