Have a 1995 peterbilt 379 with a 3406e. Just did a complete out of frame. Went to go drive to truck and the Jakes are not working like they were before the out of frame. Cruise control works and turns off when you hit the brake pedal and clutch pedal. Idle bump also works and goes off with the clutch pedal. Checked the plug on the the back of the on and off switch and is plugged up. Put a test light to it and no power to either prong (2 prong switch). Do these have power sent to them or work off grounds?
1995 with a 12.7 - but all my problems with the circuit were from ground wires being tapped into. Not a mechanic, but I believe the circuit of clutch/brake/cruise etc all run a ground circuit to activate/deactivate. Check any wiring that they may have tapped into in the engine bay to source a ground.
I will check it out. Oddly enough for it age the truck is not too hacked up nearly everything was original on the truck
Mine was pretty original too - it was something like an old ELD unit that I pulled (was a DOD truck) that triggered it. Or a cigarette lighter, something dumb. If this just occurred after the out of frame, I’d be having them run through any wiring alterations they made while you’re there, to track it down. If everything else clutch/brake/bump/cruise are working - it’s somewhere else.
Did all the work myself so I didn’t make any wiring alterations. Don’t know how to tell if the switch is going bad
Well if you think it’s switch….do what us poor folks do….go to Napa get switch(or comparable part…put it in If it worx keep it If not you know it’s not the switch….put back in box…return to Napa Rinse&repeat Good luck
One side of the switch goes to chassis ground, other side comes from ECM, so that when switch is on wires from the ECM see ground. Since it was just overhauled I would double check that both the wires are tight on all the jake solenoids under the valve covers. I see the spade ends on the wires loosen up quite often and need replacing. Wiring diagram for the jake switches goes something like this: ECM | | (2 wires from ECM to range switch, | | one for low, one for med, both see ground for high.) | | low/med/high switch | | | on/off switch | | | Ground
