Re: Hydrolic Brake failure
Confused here Bill. First, if my brakes were not working for a trailer back failure, I would know before I got off the end of my street.
And, the HPU does not run off it's own battery.
If you are using an alarm system type battery to actuate your brakes I think you should reconsider that.
The HPU should be wired into your main DC system.
Porthole:
I have a 4 battery bank system. For some reason the positive jumper to 2 of the batteries was disconnected, so 2 of the batteries were being charged and running the house 12 volt system, while the 2 "orphan" batteries were not being charged, and of course the braking accumulator got connected to the positive post of one of the "orphan" batteries. So the system worked for about 3 months until I noticed the lack of braking, and replaced the missing battery system jumper to charge the 2 "orphan" batteries.
You could just as easily have road debris hit and break a hydraulic line, have no braking in the trailer, and have no indication of that condition in the truck, unless you did the manual braking test AFTER the road debris incident.
When I started out on the trip where I realized braking was gone, I pulled out of an RV park with a dirt, large potholed, short length, driveway before connecting with a 55 mph highway where I didn't want to obstruct traffic. That afforded me no good chance to get going 15 mph and do a manual braking test when I started out. Yes, I could have done that at the first stoplight, but my mind moved on to travel and route questions and left initial pullout checks.
Being a retired electronics technician, I thought that a simple comparator circuit could alarm when there is braking voltage input to the actuator, but no braking pressure produced by the actuator, again something you would probably not realize in the truck 25 feet forward of the brake actuator, unless you did the manual braking test. The truck brakes would be stopping the entire rig. The alarm I envision could be sent to the cab by wire or wirelessly.