Thank you, I never thought of that ... the added vacuum from the engine. *slaps head*
I usually run the test on the brake before travel, so it pushes the pedal in for me a few times.. Never even thought it would bleed down the vacuum that much but you learn things every day.
I was running it as after a long bout in traffic of stop and go, the battery was going dead so I was trying to try and give it a charge as I drove.
I just bought a new battery in the middle of the last trip as it got to the point of not lasting two hours being towed, so I don't have the dead battery on arrival problem anymore. Factory battery lasted two years on the CRV with towing.
I don't have a charging wire in yet.. it's on the to do list...
It's a 9700:
Roadmaster Inc. - Tow Bars, Braking Systems & RV Accessories
I like it as it is brake actuated and no inertia switch.
Setting it for brakeaway only is a good idea if I have to do that again.
Even the light setting firmly hits the brake.
I did make some jumper cables for the occasional dead battery issues... two lengths of 10 gauge with some battery clips on them. I put one on the positive feed to the generator ( mine is in one of the back bays ) and the other to a frame ground on the MH and it is sufficient to boost the tow battery enough to start.