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Flat towing behind MH - power connection to battery

9K views 24 replies 6 participants last post by  grandriver125 
#1 ·
The wiring harness was installed but we will not be towing the Cherokee for another month. I still have to get power to the battery to keep it from going flat.

I'd be interested in learning what other members of this forum who flat tow have do to provide power to the battery from the motorhome.

Thanks
GR
 
#2 ·
In the best of cases, the tow connector on your MH already has a pin which is "hot" when the ignition is on, and it is controlled by a circuit breaker (or fuse). THe tow cable you get should have an extra wire for this power, e.g.
L-turn/Brake
R-turn/Brake
Taillight
Ground
*12vPower*
(Some MH's may be wired with separate turn and brake signals, in which case a converter may be in order).

I suggest you start by checking the connector on your motorhome; if it's a 6-pin or 7-pin, there's a good chance that it has wiring for all the above but, if it's got everything but the ignition controlled hot line you may be able to wire that line in.
 
#3 ·
We have a 7 pin and it has a positive connection (Itasca Impule 26 Silver). I just wonder if it provides enough power to keep the battery adequately charged. Reports of the battery being drained in 3 hours with the new Wiring Harness is what has given rise to my concern.

I currently only use the turn signal and brake light connections and those four wires go out to a four pin connection for mag lights. I'll have to add a power line to the positive terminal and a ground and that is where I start running into a lack of electrical knowledge. The wiring kits I've seen on the web connect right to the positive and negative terminals of the chassis battery of the MH and they have a charge regulator to ensure they don't overcharge the toad battery. Also have no idea what size positive line to run. I assume I don't need anything to the negative terminal. Is the power supply from the 7 pin already grounded?

I dumped an Escape and bought the Cherokee (for DW) in 2013 since I wanted a transfer case so I could hook up to the MH very easily and not worry about anything. So much for that idea - although we towed 6 times for 1500 miles and had no wobble.

I'm still of the view that FCA should be providing a power connection for owners who tow.

GR



ps. My first toad was a Colorado and the dealer who installed my towing package (for a 04 Journey) installed bulbs in the back. When I switched to a 07 Tahoe LTZ (and an 06 Ambassador) I went with a Blue Ox light bar that fitted into the receiver on the Tahoe. I could not use mag lights as they would have been higher than allowed by law. When I downsized the MH and toad I went with mag lights and I find them highly adequate as we only use the MH a couple times a year max.
 
#5 · (Edited)
We have a 7 pin and it has a positive connection (Itasca Impule 26 Silver). I just wonder if it provides enough power to keep the battery adequately charged. Reports of the battery being drained in 3 hours with the new Wiring Harness is what has given rise to my concern.

I currently only use the turn signal and brake light connections and those four wires go out to a four pin connection for mag lights. I'll have to add a power line to the positive terminal and a ground and that is where I start running into a lack of electrical knowledge. The wiring kits I've seen on the web connect right to the positive and negative terminals of the chassis battery of the MH and they have a charge regulator to ensure they don't overcharge the toad battery. Also have no idea what size positive line to run. I assume I don't need anything to the negative terminal. Is the power supply from the 7 pin already grounded?

I dumped an Escape and bought the Cherokee (for DW) in 2013 since I wanted a transfer case so I could hook up to the MH very easily and not worry about anything. So much for that idea - although we towed 6 times for 1500 miles and had no wobble.

I'm still of the view that FCA should be providing a power connection for owners who tow.

GR

ps. My first toad was a Colorado and the dealer who installed my towing package (for a 04 Journey) installed bulbs in the back. When I switched to a 07 Tahoe LTZ (and an 06 Ambassador) I went with a Blue Ox light bar that fitted into the receiver on the Tahoe. I could not use mag lights as they would have been higher than allowed by law. When I downsized the MH and toad I went with mag lights and I find them highly adequate as we only use the MH a couple times a year max.

If you opt for a separate cable, which sounds like your easiest solution, you could use trailer connectors at each end, using only two of the wires therein, one for ground and one for "hot". Be sure the cable is adequately sized. Based on what I have heard, a 10amp charge line (and ground) should be adequate; that line should be protected with 10 amp fuse (or circuit breaker). Also, a diode, rated accordingly should be placed in the line to prevent the MH end from drawing down the toad battery. Many have said the latter is unnecessary due to the unlikeliness of such an event but my view is that Murphy's Law is always around. :)

If you go with 10amp line make sure the cable fuse/breaker and all wiring to/from is at least 16gauge. If you feel only 7 amp is enough you could get away with 18awg wiring.

You may want to consider changing to 6-pin or 7 pin connectors at each end so you only have a single connection to deal with. You already have a ground connection with your 4-pin but that line may not be heavy enough to accommodate a charge line also.

I agree with your last sentence, "FCA should be providing a power connection". For the trouble some of us have gone through they should install a charge line, tell us the max and average current draw of the EPS system, and give us a case of beer. :)
 
#4 · (Edited)
Like rpasetto said there must be a way to get power through the harness. That's the only way that makes sense. Towing a vehicle behind a motor home has been done for decades. I'm sure that problem has been anticipated and resolved long before now.

Your best source of info will probably come from a motor home and camper supply dealer. You may have to rewire or add something and the motor home folks can probably do that for you.

I think ground between the vehicles comes from contact between the ball on tow vehicle and hitch on the towed vehicle. Sometimes it takes a few miles for rust to get rubbed off before ground is made and lights will work on my utility trailer if they haven't been used for awhile.

I've never towed a vehicle behind another vehicle so I'm guessing at a lot of this. Worst case you may have to upgrade to a stronger alternator on the motor home to keep up with having to keep so many batteries charged. Best of luck. Again, contact the experts who do this for a living. Maybe a dog chewed a wire in two.

Also as rpasetto stated chech for tripped breaker or blown fuse.
 
#6 ·
I'll let you know what we** do and how it works.

GR

**This is where I turn it over to my sos (with all the comments here) and I supervise. He has an MEng and works in the auto manufacturing biz and has also built his own race cars (DSR and GT2). That way I can blame him if anything goes wrong. I mean, a CPA isn't supposed to know a darn thing about electrical connections. :D
 
#7 ·
Finally found exactly what I want and will hope to get one in the next week or so (have to get it across the border).

It covers off the fuse and diode. It also provides a short instructional video. We will not put a connector in the front of the vehicle but will runt the wire right to the 12V pin on the 7 pin connector on the motorhome.

RVibrake Towed Battery Charger, charge line replacement
 
#8 ·
It's your prerogative to spend $50 for a fuse & holder, a diode, and 8' of 16 gauge wire.

You may want to also provide your son with the following information; much of which he probably already knows:

- The MH alternator with voltage regulation (i.e. the motorhome's charging system) will monitor/regulate the voltage and generate the current necessary to keep the toad battery charged.
- Your Itasca probably has a switched 12 volt feed (my 2010 Itasca does) which means you do not need a diode to save your toad battery draining back into the MH battery. IOW, the 12 volt feed is made by a relay that is only closed when the MH ignition is turned on. When the MH ignition is turned off, the 12 volt connection is severed; no way for the toad battery to drain into the MH battery. BTW, there is a cost in using a diode for battery isolation. My understanding it is .7 volt. That's .7 volt less pressure available to do the job.
- It's likely your MH socket has a fuse or breaker protecting the MH side of the connection.
- Your MH's 7-pin socket has a ground prong at 7 o'clock and a 12V+ prong at 1 o'clock as you are facing the socket.
- FCA's Accessory Kit to Enhance Flat Tow harness uses a 10 amp fuse to power up the Electric Power Steering. Using that estimated draw plus the draw for the tail/brake lights and potential toad battery draw, I doubled it to 20 amps max draw. 16 gauge wire will handle that for the about 10 foot stretch of umbilical cord, but I used 10 gauge because it's cheap. Did that for both the negative and positive wires between the MH and toad.
- I bought a marine-grade 10 gauge waterproof fuse holder and a 5-pack of 30 amp fuses for $10 Amazon. That goes in line close to the toad 12V+ battery connection.

My charge line cost me $10 (I had 10 gauge wire laying around my garage) and I would argue it is better than what you will get with the $50 product.
 
#9 ·
What you are saying may be true but it may also break down a bit when one considers the value of the time involved. One takes 15 minutes and the other could be much more.

GR
 
#14 ·
Just to add my two cents....I had the new Jeep harness installed. I thought the removal of a little 10 amp fuse post towing was kind of stupid so I cut and ran the live feed (put and inline 10 amp link in for kicks) to and all weather switch (with pilot light) installed on the front cowl. Now I just hit the switch and all is on/off. I all so purchased the RVi towed vehicle unit (yes I spent the $50 instead of making up my own!), the ordering process and Sam who I spoke with at the company was super. The unit is well made (US) and is very easy to install. Getting a 12V feed to the RVi unit was made a little more complicated in my case because I use a wireless toad light set up. The wireless transmitter uses a four blade plug so I have to use and adaptor off the 7 pin round plug on the motor home, I therefore had no way (at least to my weak mind) to access the live wire lug. I merely tagged into the live wire behind the MH plug and ran a two wire (live and ground) wire thru a new 4 pin round plug on the MH to a four pin round plug that I placed on the lower right corner of my license plate bracket (had to cut the plate just a little). Ran the live to the RVi unit and the ground to a ground lug on the jeep and all is perfect.
 
#20 ·
Question - where did you locate that GROUND LUG. I had look under the hood and my untrained eye didn't see one. My son has been out of town and has not had a chance to look at it yet. Hoping to do that tomorrow.

Tx
GR
 
#15 ·
I ordered the RVi product the other day and it is on the way. Glad to see you found it an easy install. I use wired mag lights so I won't encounter the same problem you did. Thanks for the update.

I'm going to bill FCA for the RVi kit. They likely need a good laugh.

GR
 
#17 ·
Have a 12 year old Brake Buddy that is still working well so no need to change and spend a bundle more. Second, Invisbrake has to connect to MH 12V so that issue still exists.

Our RVi charge unit has arrived and we may install next week.

GR
 
#18 ·
I have a couple of issues with my 12 year old Brake Buddy in that one the cleat that goes over the peddle does not fit the fat Cherokee's fat brake pedal shaft. Brake Buddy sent me their new adapter but that did not work to my satisfaction at all. I took my grinder and open up the cleat more to fir over the pedal but that approach is not ideal either. The other issue is the drivers seat face is at such and angle the Brake Buddy does not mate up well at all, couple that with the leather and the Buddy slips upwards and the push force is negated. I have tried to tip the seat bottom up as far as the electric controls will allow but it still does not work as well as it use to on my old Liberty's. Anyone have a solution other than buying and under the seat model!
 
#19 ·
I use a couple of clamps to hold the BB on to the pedal. Annoying how the pedals have changed. I also have a 2 x 4 with a piece of plywood that I put in between the seat and BB to keep it from sliding around.

PITA for sure.

GR
 
#22 ·
Nice. When I searched around that looked to me like the only possible place. Will try tomorrow.

Many thanks.

GR

ps. Talked to one of the chaps at RVi today - very helpful. Jeep should have made this a part of the harness package frankly.
 
#25 ·
My son returned and jumped right into the project.

First, we bought a 12 inch 16G 4-way trailer harness. Mail connector at one end and female at the other. Cut it in half. The half with the female connection was used under the hood (see photo). Cut off all but about 6 inches of the 12V wire from the small controller box. The green wire was connected to the black 12V wire to the box by twisting the two ends and then soldering the connection. Prior to that a heat shrink tube was slid over the green wire and after the green and black were soldered it was pulled over the connection and heat applied to shrink it. All wire to wire connections were soldered and a heat shrink applied in this manner.

The white wire was connected to the ground post just under the controller box with a ring connector that was soldered on the white wire. Care is required with that operation as the post might be a drawn arc stud - but we could not determine that with certainly (better safe than sorry). The controller was connected to the Jeep with both velcro and a zip tie. (admission - never heard of a drawn arc stud until yesterday)

From the plug that inserts into the 7 pin outlet at the motor home we ran the black 16G wire (cut off from the controller) from the 12V pin to the green wire connected to the male half of the 4 way harness (which of course connect to the green of the female end. Then a 16G wire was run from the ground pin to the white wire of the 4-way harness. The white ground wire for my mag lights was already connected to the ground pin. The brown and yellow wires of the short harness were not used of course.

Then, we (we always means “he” of course) connected the positive wire and then the negative wire from the controller to the battery and bundled the excess with a zip tie.

So, when using the toad it is just a matter of plugging the male harness connector to the female harness connector under the hood and the system is operational.

The next question was “did we do it right and does it work.” Our motorhome is at a storage yard so I backed up my SUV as it has a 7 pin connector. Put in the plug, turned on the ignition and started the engine of the Expedition. Bingo, the light on the controller box started flashing indicating that power was flowing to the Cherokee battery. We checked the voltage of the Cherokee battery with the power flowing and it was higher than without the power connection.

I have to say I’m very pleased how it worked out and I sure could not have done it on my own with the same results. I could probably do it now after the education but I still like leaving things like this to a professional.

FCA should have provided a power connection like this. If we had known that it was going to be necessary to have a harness installed (at no cost but I’ve since been told by FCA customer care that I should have paid for it!!!!) and then pay for and install a power connection, I’m not sure we would have ordered the Cherokee. It is not just these things but also the myriad of other issues we’ve encountered. We still get periodic false alarms on the emergency breaking (scares the hell out of my wife) and I regularly get a notification to put my hands back on the steering wheel when they are already clamped on at the 10 and 2 positions. I was thinking of trading my 2014 T&C for the new Pacifica. Test drove the Pacifica and I must say I really liked it. Much nicer ride than the T&C. Seems to have been very well executed. BUT, at age 74 I am not up to being a field tester like we’ve been with the Cherokee. Once was enough thank you. Now I'll wait a few years and then trade my SUV on a Pacifica if has a good reputation and the Cherokee stands up. With all the issues we've had on the Cherokee in 23,000 miles and 2 years and 9 months I'm going to pay through the nose for an extended warranty - just in case.

GR
 

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