Disconnecting the battery on 2009 Jeep Wrangler for towing

[cschemanske]

Just got a 2009 Jeep Wrangler and noticed in the manual that you need to disconnect the negative battery cable. According to this months FMCA magazine this is do to Chrysler changing the ignition switch a couple of years ago. With the switch in the on position for towing, there is still power being consumed for dash lights and radio if on. Our 2006 Rubicon did not have this problem. Anyone with a newer jeep could you shed some light on this issue.

[Rich and Cork]

Being discussed here:

Instructions on towing new 2009 Wrangler?

[takepride]

The same issue happens with other Jeeps, too (like our Grand Cherokee). I used the auxilary wire in the tow umbilical (tow plug) to supply constant power to the Jeep. I used a fuse leaving the coach battery and another arriving at the Jeep's battery, for safety. Works great, no more DOAs.

[jdoc]

You have to do the same thing if you are towing a Dodge Dakota 4x4.
Jerry

[Rick 2005 Dolphin 5376]

Just pull the IOD fuse under the hood. That's why it's there. I've towed for 10's of thousands of miles this way with no dead battery problems.

[RVersOnline]

We have an '09 Wrangler, and ditto on pull the one fuse that's obviously set up for that purpose. However I've long pondered the advice of one of the techs in the shop when we took delivery that claims you don't need to have the key turned on at all -- because the steering wheel won't lock. I tried to research that claim on the 'net, but could never find anything that corroborated that claim -- so we still pull the fuse on all but very short trips. Never experienced a DOA condition.

[wa8yxm]

One of the fun things with pulling that lead is some of these "Brake system in a box" packages like Brake Buddy... They NEED 12 volts

And even my choice of brakes.. NEEDS 12 VOLTS, can't live w/o it.

I do not offer alternatives at this time (I have a few, but they are brake system dependent)

Oh, for folks with a DP.. M&G brakes.. DO NOT CONSUME 12vdc

[NorCal C&H]

Our 2006 Jeep Liberty Diesel has the "old" ignition switch with the key position that unlocks the steering wheel but does not energize the vehicle's electronics. Some time after 2006 Chrysler went to a ignition switch without the "unlocked but not energized" position ( I can only wonder how many fractions of a cent that change saved them. Maybe it was something Daimler was already using.) - now you have to pull the fuse.

Since the vehicles have to be towed with a "key" in the ignition to avoid anyone from breaking a window, disconnecting the tow bar and driving away in my tow I had a flat metal key made that will permit me to unlock the steering but lacks the internal microchip needed to drive the vehicle any distance. Without the chip the engine will start and run for about five seconds then die. If you attempt to restart the engine something like 3-4 times with the flat metal key (w/o chip) you have to take the vehicle to the dealer to have the computer reset. I also put a padlock in one of the tow bar pin holes instead of the clip pin.

And to RVerOnline - a key MUST be in the ignition and turned to the unlocked position. I know from experience! Most owners manuals have a section on towing and address the key / steering wheel unlock subject. I have the corner of the page turned back in my manual so I can quickly find the steps.

Harold

[donie]

FWIW, according to the 09 manual, on Page 362, it gives the steps required to tow a Jeep.
1) Turn engine off
2) Depress brake pedal
3) Shift transmission into Neutral or depress clutch pedal
4) Shift transfer case lever into N ( Neutral)
5) Start engine
6) Shift automatic trans into Drive or Manual into gear
7) Release brake pedal and ensure that there is no vehicle movement
8) Shut engine off and place the ignition key into the ACC position
9) Shift Auto Trans into Park
10) Apply Parking Brake
11) Attatch vehicle to tow vehicle with tow bar
12)Release parking brake
13) Disconnect the negative battery cable and secure it away from negative post.

The setup we have installed has a circuit for the trickle charging of the toad battery while towing, so I cant see removing the neg cable.
Maybe Im wrong.

[RVersOnline]

I suspect different vintage Wranglers may have different electrical options. When I first read the manual, which reads as in the prior post, I was surprised to see the reference to disconnecting the battery while towing. After researching the issue a bit, I discovered the reference to the fuse that is so obviously set up for a temporary disconnect; and learned other Wranger owners were opting for this easier solution. It's my impression there have been changes to the design that are not reflected in the manual. And we've found other references in the manual that are not accurate. On our '09 we *do* use the key, and pull the fuse for anything longer than short hops. However, even with the fuse pulled one of the two power outlets stays hot, so there is no issue in powering the Brake Buddy. Even more interesting is the advice provided by the selling dealer that the key is not even needed to "unlock" the steering wheel on the '09s. I'll confess I'm able to turn the wheel manually hard in both directions with the key out, and it does not appear to lock. If that's the case, I'm not certain it's even necessary to have the key even in the ignition while towing. But I've never seen any confirmation of that fact, so we keep the key in/fuse pulled -- even though that may just be an unnecessary procedure.

[Rich and Cork]

Quote:

Originally Posted by RVersOnline Even more interesting is the advice provided by the selling dealer that the key is not even needed to "unlock" the steering wheel on the '09s. I'll confess I'm able to turn the wheel manually hard in both directions with the key out, and it does not appear to lock. If that's the case, I'm not certain it's even necessary to have the key even in the ignition while towing. But I've never seen any confirmation of that fact, so we keep the key in/fuse pulled -- even though that may just be an unnecessary procedure.

Take a look at the reference in my post #2. I verified that my '08 Rubicon steering wheel locks after a half turn and my neighbor's '09 Rubicon does not with the key out.

Just got back from my first longer tow with the US Gear setup. I only pulled the M1 fuse (so there would not be an interaction with the turn signals and the brakes being actuated by the in-cab brake pulling solenoid). I put the key in the first position. I feel the US Gear setup with the power going from the Motorhome to the Jeep battery is sufficient for me.

[takepride]

Rich:

On your setup, the brake light on the toad should not matter if the signal comes from the toad or the motorhome. It ought to have a diode that allows only one signal through at a time (the first one to arrive at the diode) and prevents it from traveling "backwards", notifying the US Gear "brain" of a brake application (if you have the PCM 6002). With the US Gear setup, your 12v from the coach and the 12v from the toad are both available anyway (and compatible). It keeps the toad battery up and/or not being discharged. The in-line fuse/circuit breaker doesn't separate the two charging systems and batteries it only protects against passing an over-current or spike. Pulling the fuse is for tow situations where you are not supplying a constant 12v through the umbilical, though I'm sure it doesn't hurt anything either.

[CoolTech]

Quote:

On your setup, the brake light on the toad should not matter if the signal comes from the toad or the motorhome. It ought to have a diode that allows only one signal through at a time (the first one to arrive at the diode) and prevents it from traveling "backwards", notifying the US Gear "brain" of a brake application (if you have the PCM 6002).

We need to clarify a few things here. First off is the function of a diode. A diode will allow current to flow one way down a wire and NOT the other way. A diode has no notion of a signal arriving first etc.

Rich and Cork is correct in that the M1 fuse needs to be pulled on a 2007+ Jeep Wrangler when an in-vehicle braking device is used. The MH needs to be able to send current down the wire while towing and the brake pedal will also try to send current while depressed. The "constant" current from the Jeep's own brake pedal will negate a "pulsing" turn-signal signal from the MH. The effect with the M1 fuse in place is that the toad will "lose" it's turn-signal pulsing whenever the MH brakes (and activates the in-car brake device). No kind of diode installation will address this - as both the MH and Jeep do need to flow current..... but the problem is the concurrency!

But, speaking of diodes, they should really be avoided all together in the 2007+ Jeep Wranglers. A diode-based tow harness kit is simply very old-school in a very modern electrical system Jeep. The new Jeeps are a CAN-BUS design and, oversimplfying, the switches in the jeep really aren't switching current at all. Rather, there are placing a signal on the Jeep's on-board computer network (BUS) and the Power Distribution Module is monitoring the network and takes the appropriate action.

I recommend a seperate bulb and socket solution in each rear tail light - although this is harder with the new tail lights. Last choice would be an "old-fashioned" diode-based solution. Inherently, there's nothing really wrong with the diode solution but the install points into the OEM wiring are typically failure vulnerability points... and there's no need for this when superior alternatives exist.