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Topic: Tow Jeep Electrical Failure (Read 780 times) previous topic - next topic

Tow Jeep Electrical Failure

When towing our 2012 Wrangler, I noticed the coach start battery bank voltages changing between 11.8 and 12.1. 

I started the coach generator and it raised  the battery voltage to fluctuate to 12.8-13.6

I stopped in about ten minutes and disconnected the Jeep.  The coach start battery  came to steady 13.6-14.

Then I cranked the Jeep and drove it a few hundred yards where it went completely dead.  In that few hundred  yards the headlights rapidly blinked on and off, the dash lights dimmed and blinked and went off, the light controls would not work to turn them off, and finally only the small signal lights were blinking faintly as the car died.

Ideas of what did what to what?  Did the coach system harm the Jeep as we were towing it or did something in the Jeep cause some draw on the Coachb start batteries that I was seeing as lowered battery voltage as I was driving?

Very odd!!

Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Tow Jeep Electrical Failure

Reply #1 –
Quote from: Michael & Jackie –
Then I cranked the Jeep and drove it a few hundred yards where it went completely dead.

...or did something in the Jeep cause some draw on the Coach...

Sounds like the smoke was let out of the Jeep alternator or voltage regulator, since it could not keep the engine running.

Not knowing how the Jeep and your coach are wired together when towing, hard to say what caused what.  But you will certainly need to get the Jeep looked at by electrical system techs.

I'm going to guess that the Jeep was for some reason causing a BIG load on the coach electrical system.

I would think the 12 volt supply wire from the coach to the Jeep would be protected by a fuse.  If so, surprised it did not blow.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Tow Jeep Electrical Failure

Reply #2 –
Michael,

I cannot even hazard a guess as to what did what  to what.  However, I regularly tow my 2011 Wrangler Unlimited and will be quite interested in what you find.  Keep us posted please. 

Richard
Jan & Richard Witt
1999 U-320  36ft WTFE
Build Number: 5478 Motorcade: 16599
2011 Jeep Wrangler Unlimited w/Air Force One
Jan: NO5U, Richard:KA5RIW
The selected media item is not currently available.

Re: Tow Jeep Electrical Failure

Reply #3 –
Shorted or open battery?
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Tow Jeep Electrical Failure

Reply #4 –
Mike, my first guess is that the Jeep battery has failed.  Ours lasted about 5 years.  If you have a 12v connection to the Jeep from the coach it should (must) be protected by a fuse at the coach end.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Tow Jeep Electrical Failure

Reply #5 –
Quote from: Roger & Susan in Home2 –
Mike, my first guess is that the Jeep battery has failed.  Ours lasted about 5 years.  If you have a 12v connection to the Jeep from the coach it should (must) be protected by a fuse at the coach end.

Actually, the charge wire needs a fuse at BOTH coach battery and toad battery end.  Either battery, were the charge wire to rub to bare metal would be a DEAD SHORT.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Tow Jeep Electrical Failure

Reply #6 –
Brett is correct, a fuse belongs close to any source of power and if two are connected a fuse at each end is best practice.

OEM wiring in our coaches between the batteries and inverter/charger has only one fuse between the coach common + post and the inverter. There should be a fuse at the battery end.  Picture is from install prior to tidying up the small wires.  400 amp fuse.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Tow Jeep Electrical Failure

Reply #7 –
Quote from: Roger & Susan in Home2 –

OEM wiring in our coaches between the batteries and inverter/charger has only one fuse between the coach common + post and the inverter. There should be a fuse at the battery end.

Yes, the large-gauge positive wire to the inverter or inverter/charger should have a  single properly sized slow burn fuse (amp rating depends on wire gauge and inverter amp rating).  And nearer the battery is always safer-- less chance of insulation rubbing through and contacting metal/chassis ground which would be a dead short.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Tow Jeep Electrical Failure

Reply #8 –
It sounds like there was a lot of power dissipated somewhere.  Use your eyes and nose to sniff around the Jeep for burnt or melted wiring.  It could have gone into the battery too, which would have cooled by now but if you can't determine anything else I would start there by pulling the battery and taking it in somewhere to have it checked.  If you have a separate charger you could see if it responds to charging or lugs it down.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho

Re: Tow Jeep Electrical Failure

Reply #9 –
Latest info

Had a tow truck coming but canceled right before he came and I have an appointment for tomorrow at Jeep.,

Last night after Jeep died, I found one Jeep battery post covered in corrosion material (a white salt, sulfate?).  I dissolved with baking soda, cleaned and let dry.  This morning I reconnected battery to Jeep and it started.  Good but....

Was the coach electrical system harmed in this episode for I have no idea what was going on.....why would a towed jeep have such an electrical draw on the coach?  But if it did, any harm done?

Coach today, 12 hours after episode, shows a bit over 13 volt at start batteries without engine running, and the house battery show about 14 volt.

I noted that one of you said a short or open (?) battery could be the problem.

Now you raise the fuse question and I do not know that answer.    Will try to see. 

Battery bought May, 2018.  Will take a photo to see if fuse there,  It was bought as a system check said it was spinning the starter too slowly.

As always, thanks for your time, interest and help.
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Tow Jeep Electrical Failure

Reply #10 –
Battery tested good but acid leaked up post and disrupted connection.  I guess that means the jeep was drawing more amperage than normal to keep the lights and brake available?
Mike
2001 U320 4010 Build 5878 (Gus)
Wrangle Unlimited Toad
Nacogdoches

Re: Tow Jeep Electrical Failure

Reply #11 –
I am installing this on our Jeep, on the incoming charge line from coach.  (one way diode)  Roadmaster Single Diode  Item # RM-690    https://www.etrailer.com/Accessories-and-Parts/Roadmaster/RM-690.html

To clarify, I am adding the above to this charge line kit:  Roadmaster Battery Charge Line Kit for Towed Vehicles Item # RM-156-25  https://www.etrailer.com/Accessories-and-Parts/Roadmaster/RM-156-25.html 



Dan - Full timing since 2009
2003 U320 40' Tag 2 slide

Re: Tow Jeep Electrical Failure

Reply #12 –
My Jeep tows with the ignition off and the braking system doesn't use power, so I don't need a charging system.

My MDX often arrived with a dead battery, so I added my own charging system, using the otherwise unused center terminal on the trailer lights connector. My cable already has wires on all connectors, so all I needed was a wire on each end through a circuit breaker to each vehicle battery. No diode,  although I did buy one.  Piece of cake and works like a charm, although I got well practiced for a time in jump starting the MDX.
Tom Lang K6PG (originally  KC6UEC)
and Diane Lang
2003 38 U295 build 6209
2016 Jeep Grand Cherokee Summit Ecodiesel
still have tow-ready 2006 Acura MDX 
Temple City, California
Motorcade 16681 California Chapter President
SKP 16663 member of SKP Park of the Sierra, Coarsegold California
FMCA F071251
Retired electrical and electronic engineer

Re: Tow Jeep Electrical Failure

Reply #13 –
Our Jeep rides with the key off and a wire harness that taps in just before the tail light fixtures using 12 volts from the coach to make the brake lights work thru the trailer light connection so I don't understand why the Jeep would need a external charge system.


Keith
The selected media item is not currently available.Keith & Jo
2003 U320T 4025 PBBS Designer series
Build 6203    Cummins 500hp
2000 U320 4010 WTFE / Build 5762 —Sold—
Motorcade #18070   
Pasadena, Texas
2015 Jeep Wrangler Sahara-Sunset Orange pearl coat
Don't argue with a fool, people watching might not be able to tell the difference.

Re: Tow Jeep Electrical Failure

Reply #14 –
Quote from: hdff –
Our Jeep rides with the key off and a wire harness that taps in just before the tail light fixtures using 12 volts from the coach to make the brake lights work thru the trailer light connection so I don't understand why the Jeep would need a external charge system.


Keith

One example for needing external power is to run a toad brake system that has to be plugged into the toad for the compressor.  I use the RVI3 system, that has a built in compressor, that plugs into the hot jeep acc. plug.  I was told and now after 4 years of towing know that the Jeep Grand Cherokee has enough battery for a day's tow.  But RVI kindly included the system to add to charge the Jeep will towing if I ever had problems.
Dave Cobb
Buckhorn Lake Resort The Club, #6202, Kerrville TX
check the map.  I do rent it out when I am traveling!
2001, U320, 36' #5887, in Kerrville, FT Club #17006, (7/23 to present)
2024 Jeep Grand Cherokee L, Summit, white
EX: 98 U295, 36' #5219, (mid door), (4/13-10/23)
EX: 93 U225, 36' (4/11 to 4/13)