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Guest Message by DevFuse

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Is The C-Max Energi Really Flat Tow-able? My experience says maybe not!

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4 replies to this topic

#1 OFFLINE   John A Smith

John A Smith

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Posted 01 July 2017 - 03:30 PM

My experience was horrific. I bought a brand new RViBrake3 which comes with a Wi-Fi tablet that allows you to remotely set and monitor the toads brake unit. The first chance I got to test it was 2,000 miles from home where we drove our C-Max Energi to pick up our new motorhome. This would be my 3rd toad and 3rd Class A so I am not new at this. The only questions were regarding active brakes and the correct ignition position. I have it in writing from Ford that any C-Max should be towed in neutral with the ignition off. I have it in writing from RViBrake “The C-Max brake pedal acts like a 'dead pedal'. You are to run the RVi3 in the Vacuum 'Compact Car' set point.” I doubted this so tested it by coasting down a long hill in neutral with the ignition off. Sure enough it acted like a regular vacuum system, some assist for a couple of brake attempts then it required a lot of effort. Sorry if it took so long to get to the point but I thought setting the scenario was important. Now the horror story:
Before I left I installed new Michelin tires on my C-Max. I had it all ready to be towed including the RViBrake3. I set it exactly as the company told me it should be set. Everything seemed fine for the first 15 or 20 minutes until I was on a highway doing about 55. When I applied my brakes to come to a normal stop the brake unit jammed on my brakes locking them up completely. I could see smoke in my rear view monitor as I dragged the car until the unit released. I had no way to pull off the road for quite a while during which the brakes locked up two more times. Finally I was able to get it disconnected and continued on without toad brakes. When I was able to contact the manufacturer they suggested a different setting which I tested in a controlled situation. This time I set it to “active” along with the lowest pressure setting of 5 pound. At about 10 MPH I pressed the test button only to have the brake engage hard enough to jerk the motorhome. I had to make the 2,000 trip home without the brake unit. It was difficult at first because the MH brakes weren't broke in. Bottom line, the trip home was difficult. The first time I drove the C-Max after the three major lockup’s I got that horrible thump, thump sound indicating the tires were damaged. One actually had a flat spot down to the wear warning bar. Towing it home like that was scary but fortunately we made it home safe. I just went back to Costco and had all four tires replaced again with just a bit over 4,000 miles including the tow miles that did not register on the odometer. 
I have nothing bad to say about the company at this point. They admit I did nothing wrong and are bewildered at what exactly caused this. I think they will take my RVibrake3 back and pay for my tires.   All I have asked for is they making me whole and I expect they will. 


Next I decided to go with the Patriot 1 since it has a simple 0 to 9 brake pressure selector.  A couple of weeks ago my first test while towing behind my pickup went well.  I set the new Patriot to #3 before I could feel brakes engaging on the C-Max.  #1 and #2 engaged too gently to feel any pullback.  Today I took it out for a real road test behind the motorhome and got a quite a surprise, the C-Max skidded at setting #2.  I did pump the C-Max brakes and the ignition had not been turned on since.  There is only one logical explanation for this; the C-Max must be spontaneously reactivating the power (active) brakes even with ignition off.  When I switched to setting #1 it didn't happen again but who knows what could happen since it is so unpredictable.  I'm seriously considering putting a shutoff switch on the 12 volt battery.  In afterthought I can't disconnect the 12 volt battery because then the Patriot would have no power.  Maybe there's a single fuse that would interrupt the active brakes.  Or I could go ahead and disconnect the C-Max 12 volt battery and connect the 20 amp charge circuit from the MH to the Patriot.  Since the Patriot has a built in backup battery it would still function in case of breakaway.   Any ideas would be appreciated.  I have way too much invested to start over with another toad.  

Edited by John A Smith, 01 July 2017 - 03:30 PM.

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#2 ONLINE   rbort


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Posted 01 July 2017 - 03:45 PM

I think the Cmax periodically recharges the brakes (you hear that pump) when you access the car or turn the car on.  It may be detecting the car is in motion and recharging the brakes just like when you open the door and not even have the ignition on.  If you don't want that to happen then you would have to disconnect the 12v battery for the Cmax or find the fuse for the brake booster if they have one.


Just a thought.



#3 OFFLINE   mangles


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Posted 16 July 2017 - 01:14 PM

Hi John


Here's a link to a posting in the CMAX hybrid forum in which the owner pulls fuse #9 to prevent the electric vacuum pump from operating.  I have verified this is the correct fuse in my shop manual.


re, mike angles




#4 OFFLINE   fotomoto


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Posted 17 July 2017 - 06:47 AM

Agree with others, they system can and will pump up pressure with the car off.  I suspect these TOAD brake systems are electronically periodically waking the car up and it auto-pumps the brake system just like if you open the drivers door.  

#5 OFFLINE   mangles


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Posted 17 August 2017 - 06:15 PM

Hi John


Thanks for you posting.  It forced me to make one last phone call on potential options for us.  First, to answer your question, I have not been able to test my CMax towing with the fuse out behind my RV.  Currently my CMax is at the dealer for some other recall work (modem/radio and door latches).  Which they, the dealer, after a week can't seem to get the job done.


But, on the good news front, I had a 4-wheel alignment completed in which all was at factory spec.  Also not frame issues, which I did not expect as I had not encountered the brake lockup issue.


A week or so ago, Dick mentioned that Roadmaster may have a solution as they make various fuse bypass switches.  Today I called.  With enough words I found myself speaking with Graham Dudik (800-669-9690, ext 139).


I learned much from Graham, including that he and Dick have spoken at length.  Graham still has some reservations with by-passing fuse #9.  His main concern was the generation of a DTC fault if the car where started with the by-pass on, preventing the vacuum pump from running.  While there is no way to prevent a DTC event, I told him that I had learned if one tries to drive the car with the by-pass on in the tow position(fuse removed), the engine will start and create the needed vacuum for braking. Additionally the DTC will clear itself after a few good engine starts.


Soon into our conversation Graham told me Roadmaster does not have an application or tech note on their web site for the CMax vacuum pump fuse.  But they have just developed a relay based fuse bypass that is controlled by a switch placed in the driver's area.  The part number is JK76517. Priced at $150 it is not inexpensive, especially for a $10 relay, and some simple engineering work etc.


Graham, told me they are special order only at this time as there have been so few situations of CMax owners encountering the braking issue.  Hence, most don't know there is a potential issue.  I did order a JK76517 which shall take two weeks or so to get it as it is a special order, build to order.  Which brings me back to my CMax.


As I mentioned it is at the dealer.  Normally I do all my own maintenance, but the aforementioned repairs are Ford recalls with exception of the front end alignment.  With just 16k miles, I would expect the alignment to be true and would not typically waste my money unless I noticed a need for it. 


In talking to the service tech at Ford, who started our conversation with the "tow with the ignition off to ensure the likes of the vacuum pump doesn't turn on"... Which based on what we know is wrong, that is, the vacuum pump can turn-on anytime for some CMax Energi's.  Anyway, I told him that my mileage range for the big battery was now approaching 40 miles for a car/battery that Ford gives us a 22 mile range on.  He told me that the regen continuous to operate when I flat tow and that the large battery indicator range will be influenced by averaging the miles traveled without the ICE.


So, in the same breath he told me when everything is off, the vacuum pump will not operate, and that the little car brain continues to measure mileage traveled which it then merges into the miles traveled into the electrics average, resulting in an increasing display count.  I said you can't have it both ways...Is there someone at Ford I can speak with??


Bottom line, no one at Ford wants to talk to us.  And from my standpoint no one really cares to understand the problem.  I think the only way to get Fords attention is to file a complaint at https://www.nhtsa.gov/recalls


As a final note here, I just finished calling Ford Support (800-392-3673) where I spoke to an Energi support person, I told him I needed a Ford case number associated with my car and the brake lockup issue for filing a complaint with the nhtsa. 


He understood and provided the case reference number (CAS12947427) . If you have not done so, I recommend you also open a case with Ford, be sure to tell them it is a safety issue with brake lockups on the highway.  Somewhere, someone at Ford should see this and start asking questions (I hope). 


Doing so, perhaps while the car is still under warranty may help us get post warranty work/repairs covered if they are related to the brake lockup issue. Additionally, if there is an event, we can cite this case number to our insurance company as a show of good faith in trying to address the issue. If enough of us do this, the nhtsa may reach out to Ford for a response and correction.


Lastly, I am going to post this info on the Ford Energi forum and to my CMax paper on my web site.  I will try to add it to your original posting. Perhaps someone from Ford will take notice...


re, mike

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