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Brake Problem when towing FFH

towing active brakes brake problems

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3 replies to this topic

#1 OFFLINE   Habart

Habart

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Posted 19 November 2016 - 10:50 PM

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? 









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#2 OFFLINE   murphy

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Posted 20 November 2016 - 06:37 AM

Did you connect your "charge line" to the jumper terminals under the hood?  If connected directly to the battery terminals that makes it impossible for the car to accurately monitor the charge state of the battery.  There are sensors on the regular battery connections that allow the car's computer to monitor current flow into and out of the battery.

 

The FFH vacuum assist brakes get their vacuum from an electrically operated vacuum pump.  The car can be driven up to 2 miles with the engine not running so no engine vacuum would be available.  If you pull the fuse for the vacuum pump, power braking should not be possible.



#3 OFFLINE   Habart

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Posted 20 November 2016 - 06:36 PM

Yes, the charge line was connected to the posts under the hood, so it shouldn't be a problem with that.

 

Good thought about looking for a fuse for the vacuum pump for the brakes. I will have to double check the manual to see if I can identify the correct fuse (I think I have looked for this before, but couldn't identify a specific fuse).

 

Someone described modern cars as computers with wheels. I think this applies doubly with hybrids. I keep wondering if there is regenerative braking going on when the InvisiBrake pushes the brake pedal, and maybe something happens when regeneration has fully charged the battery (gee, I need more braking, maybe I (the computer) had better turn on the power brakes). The other change that has happened is that there is now a relay in the brake light line so that when the InvisiBrake pushes the brake pedal the brake lights don't come on and override a turn signal. How the car actually works is now buried in the computer software, and likely only one of the Ford programmers could answer these questions, and as a customer, I don't get to talk to them.

 

However, if it was any of these two issues, it should be a common problem with anyone to tows an FFH or a C-Max, and I haven't found any reference to this. 



#4 OFFLINE   Habart

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Posted 07 December 2016 - 06:57 PM

Some more news. Had the FHH in for service, and found two things.

1. There were a number of error codes regarding communications failures between computer modules in the car. Unfortunately the computer tech didn't keep a record of the codes, he just deleted them  :drop: . So I will have to wait to see if they reoccur.

2. There was some communications with Ford's tech support, and I found out that they now say that, when towing, it is necessary to stop every 500 miles and start the motor. The concern seems to be that the oil can overheat, and by starting the motor, the oil is forced though the cooler. I haven't seen this in either the 2013 manual, or in the revised towing procedures from 2013. However it is now in their summary towing guide that lists which Ford vehicles that can be towed.







Also tagged with one or more of these keywords: towing, active brakes, brake problems

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