I agree with Brett. I always check our exhaust brake (and our new variable vane turbo brake) as he said. You can feel the brake take effect when you turn the switch, and let up when the switch is turned off. We have had 3 motorhomes with PAC brakes, and our new one has the variable vane turbo. They all "feel" the same to me and as far as I can tell are equally effective. But Brett's process is the only way I know sitting in the driver's seat that the brake is working or not.
Ed Headington
2013 Cummins 6.7 ISB engine
