I have a 2013 FFH that we tow behind a Leisure Travel Van B+ RV (Mercedes Sprinter Chassis)
The FFH is set up with a charging line from the RV, and I have a Roadmaster InvisiBrake system installed. I have two persistent problems, and would like to know if any others have experienced these problems, and / or found solutions.
1. After towing, about 25% of the time the car will get the "wrench" and transmission error code. This disappears after one or two start-ups when driving the car. The dealer (and I) don't think this is a big issue as the code always resets, and when in for service, no codes are showing. I have had the "random code" problem with a previous Olds Alero that I used to tow with another RV.
2. The FFH does not have active brakes (i.e.: there is no power brake boost when towing). The InvisiBrake is set to about 70 lbs pressure, which seems about right so that when braking the car feels to be putting minimal pressure on the tow bar. The Roadmaster instructions suggest 60 lbs, but after road testing with the tech, we upped the pressure a bit. Now the bad part. On a long road trip (3 months), about once out of every 5 days of towing, when applying the brakes in the RV, the FFH seems to go into "panic braking" and trys to stop the motorhome. When this happens, I have to pull to the side of the road (the brakes on the FFH are very hot - as expected as it is trying to stop an 11,000 lb motorhome). I then go through the normal towing start procedure (put the FHH in park, start the motor and let it run for a bit, put the car in neutral, and turn off the ignition (push button start). Then everything is back to normal, and I am likely good for another week.
I think the cause of the problem is that, for some reason, the vacuum assist on the FFH is powering on while driving, and the next time I touch the brakes, the InvisiBrake is applying 70 PSI to power brakes, not to unassisted brakes, and hence the "panic" braking. I don't think the InvisiBrake is causing the problem, as it has a mechanical control for the brake pressure. The dealer has check for any bulletins that might be related to this problem, but hasn't found any. He is unable (or unwilling) to call Ford directly as he has never seen the problem "firsthand" (and likely never will unless he goes RVing with us).
Any thoughts on how to proceed? I have tried to check for voltage problems, as I do have a charge line, and there weren't any after I had pulled off the road. But if it was a transient problem, I likely wouldn't have found it anyway, so not conclusive. I am thinking of buying a portable OBD reader, but the service manager said that the aftermarket ones may not be able to read all the codes. I have talked to Roadmaster, but they say they have never encountered the problem, and their only suggestion is to drop the brake pressure to 30 PSI, which would likely solve the "panic braking", but would give only minimal braking the rest of the time. Any other thoughts?