You have either a short to ground or short to power somewhere. You can either trace the harness wiring and repair it, or replace the harness outright.
At the front of the AC compressor....
Clutch switches are usually located at the top of the clutch pedal.
Clutch safety switches are usually mounted under the dashboard above the clutch pedal, so that they are activated when the clutch is depressed.
You may have some bare wires that are shorting out on the clutch pedal. Get under the dash and check it out.
You have 2 switches A and B above clutch petal under dash
the a/c clutch is loose and is shorting out. the compressor and clutch must be replaced
Start out by checking the freon levels and if that is okay then check the pressure switches and the wire harness to the clutch....
Vacuum lines, clutch switches, ...
low or out of fluid (new car) classic car linkage may have broken
There's several different manufacturers of PTO systems out there. In simple terms, you engage the clutch, engage the PTO, release the clutch, then use the corresponding lever to raise or lower the dump body.
The transmissions aren't made by Freightliner, and this answer applies to all commercial truck manufacturers. A fully automatic transmission is clutch free. An autoshift basically adds a synchroniser gear and computer operated shift mechanism to a manual transmission, and still uses a clutch. With an autoshift, poor clutch manipulation often causes the synchroniser gear to go out, making the transmission unable to shift. On a fully automatic transmission, that problem does not exist.
There are a bunch of switches that can keep the clutch from activating, low refrigerant pressure is the most common.