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Anyone have an electrical diagram of the m939 series trucks? I was unable to find one in the tm's or on the internet.I think that would help alot of my electrical questions related to the truck.

Ok that helps i also tried putting the voltage meter with the positive on the wire right where it plugs into the valve and the negative on the body of the truck (ground). I got nothing from either wire so that probably tells me that the positive power isn't getting to the horn but the negative...

Ok like i said before i hate electrical wiring. So today i was going to try to get the air horn functioning properly but i failed. So i first started by seeing if the air valve worked so i hooked up a 12v battery to it and it clicked like its supposed to. Next i checked to see if i have air to...