I had mentioned in other threads my wanting a pyrometer.
The coach came with a thermocouple attached to a threaded hole in the side of the Pacbrake housing. The thermocouple led to an electric sender, to a wire, across the bottom of the coach, to the helm, to.... nothing! For whatever reason, a previous owner had removed the gauge. I tried to find a single-wire gauge to use the existing setup, but could not find. I ordered a gauge, sender, and wire from an online seller.
I removed the old thermocouple and tried to install the new. The attachment nut was too large, but it was easily removed to reveal a smaller, proper-sized thread. The thermocouple is the same length as the old, but would not go completely into the threaded hole. The flap in the Pacbrake was blocking it! The old sender was keeping the Pacbrake from closing completely! No wonder the braking action seemed weak.
I purchased a 1" length galvanized pipe and a short combiner from our local hardware store, and installed the thermocouple. The pipe moved the thermocouple out about an inch, which allows the sensor bulb to clear the Pacbrake flap, yet remain in the exhaust path. I ran the wires along the bottom of the coach, held with metal tape. (Yeah, I know...) I removed the dead VDO clock from just above the steering column and installed the new gauge. It was impossible for me to get my big hands underneath all of that stuff in there to attach the mounting bracket from the rear. I would have accidentally disconnected half the dash wiring! I used a bit of foam tape to augment the nice friction fit of the gauge in the hole. Working gauge!!
I have not been on a road trip yet, but I expect the Pacbrake to work much better now.