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  #97  
Old 08-24-2016, 10:50 AM
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Re: 2014 Jeep Cherokee rv tow wobble

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Originally Posted by Array View Post
That should work and sounds like the easiest solution. When the umbilical cord is plugged in, the relay in FCA's harness is energized which connects the KL's power to the power steering module.
Sorry about the long previous post. I just want to be clear that my method would connect the MH power source, not the KL's power, to the power steering module.

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  #98  
Old 08-24-2016, 01:56 PM
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Re: 2014 Jeep Cherokee rv tow wobble

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Originally Posted by MrK454 View Post
I am assuming that re-routing the circuit to utilize the MH's 12v power rather than the 12 volts from the Battery Distribution Center's connection would not adversely affect the operation of the Power Steering, and "the relay in FCA's harness" was one of the questions I have. Do you know where the dealer installs that relay, as I don't see it under the hood. It would seem to me that the relay would be in the circuit that activates the electric power steering, the circuit into which we insert the fuse.

I just went to check the amperage draw on that circuit. I tested at the point where the fuse would go, and found a draw of 0.19 amps. When I made the connection, I could hear an audible "click", akin to a relay engaging. Unless the current draw is greater when the vehicle is being towed, it would seem to be an insignificant draw on the Jeep's battery and no need to run the Jeep every three hours to keep the battery charged.

In my case, I have an air-actuated braking system, so the only draw on the Jeep's battery is for the occasional illumination of the brake lights. Power for other lighting (directional signals and running lights) is from my motorhome. It would seem to make sense to re-route the circuit with the fuse directly into my MH's 12v so that I can leave the fuse in place and make the connection to it when I connect the 'umbilical cord'.
They installed my harness relay on the driver's side wheel well low and next to the battery.

The wire and fuse connected to the PDC only energize the coil in the relay. That's why it draws so little amperage. The contacts in the relay actually connect the power steering module to the KL's battery. I measured the amps draw at the battery when the power steering module was powered up and it came in from 1 amp to over 20 amps depending on how fast the steering wheel was being turned.

Since the FCA harness relay connects the power steering with the KL's battery, FCA estimate the battery will last 3 hours. If you install a charge line to keep the KL's battery charged while towing and also use that line to energize the tow kit harness relay, make sure you isolate the KL's battery from the relay with a diode or a relay.
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  #99  
Old 08-24-2016, 03:40 PM
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Re: 2014 Jeep Cherokee rv tow wobble

Quote:
Originally Posted by Array View Post
They installed my harness relay on the driver's side wheel well low and next to the battery.

The wire and fuse connected to the PDC only energize the coil in the relay. That's why it draws so little amperage. The contacts in the relay actually connect the power steering module to the KL's battery. I measured the amps draw at the battery when the power steering module was powered up and it came in from 1 amp to over 20 amps depending on how fast the steering wheel was being turned.

Since the FCA harness relay connects the power steering with the KL's battery, FCA estimate the battery will last 3 hours. If you install a charge line to keep the KL's battery charged while towing and also use that line to energize the tow kit harness relay, make sure you isolate the KL's battery from the relay with a diode or a relay.

Aha, so the power steering does use more power when it's moving/turning than the stationary draw. I can now see where FCA might suggest a three hour interval for recharging.

Although you've measured in excess of a 20-amp draw, I imagine that it is a momentary draw, therefore the 10-amp fuse is adequate to protect the circuit. I guess I need to double-check my MH's 12v output. If its circuitry takes the power from the MH chassis batteries to the front of the MH and then all the way back to the rear, I can envision a considerable voltage drop. And wouldn't that, in turn, require a higher amperage draw in order to support the power requirements of the power steering, possibly exceeding the 10 amp fuse's capacity? Looks like I need to trace some wires on the MH.

I really appreciate the information from you all. What sometimes looks like a simple solution may, in fact, create a whole new set of issues. But I still hate the "solution" that FCA came up with!

Dale
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  #100  
Old 08-24-2016, 04:39 PM
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Quote:
Originally Posted by MrK454 View Post

Aha, so the power steering does use more power when it's moving/turning than the stationary draw. I can now see where FCA might suggest a three hour interval for recharging.

Although you've measured in excess of a 20-amp draw, I imagine that it is a momentary draw, therefore the 10-amp fuse is adequate to protect the circuit. I guess I need to double-check my MH's 12v output. If its circuitry takes the power from the MH chassis batteries to the front of the MH and then all the way back to the rear, I can envision a considerable voltage drop. And wouldn't that, in turn, require a higher amperage draw in order to support the power requirements of the power steering, possibly exceeding the 10 amp fuse's capacity? Looks like I need to trace some wires on the MH.

I really appreciate the information from you all. What sometimes looks like a simple solution may, in fact, create a whole new set of issues. But I still hate the "solution" that FCA came up with!

Dale
That 10 amp fuse protects the relay's coil. It's a separate circuit from the part of the relay that's carrying the current required to drive the power steering motor.

A relay is like a remote control switch. When its coil is energized the switch closes which typically carries much more current. It takes very little current to drive the coil to close the switch. The contacts in the switch part might be rated for 30 amps, for example.
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  #101  
Old 08-24-2016, 09:37 PM
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Re: 2014 Jeep Cherokee rv tow wobble

Quote:
Originally Posted by Array View Post
That 10 amp fuse protects the relay's coil. It's a separate circuit from the part of the relay that's carrying the current required to drive the power steering motor.

A relay is like a remote control switch. When its coil is energized the switch closes which typically carries much more current. It takes very little current to drive the coil to close the switch. The contacts in the switch part might be rated for 30 amps, for example.
So, the power to operate the power steering doesn't go through the 10-amp fuse circuit, but through the relay, which provides the power from the Jeep battery. I think I've finally got it.

Using my MH to provide power to the fused circuit will eliminate the need to install and remove the fuse, but the Jeep battery will still be at risk of discharge if the jeep isn't started to recharge the battery, or if a supplemental charge isn't applied to the battery. It should be a simple matter to use the same 12v+ source from the MH to power both the fused circuit and, with a diode, keep the battery charged.

Thanks again to all, especially to Array, who have pointed the way through this quagmire. I'll still use the switch inside the console, but I'll be freed from popping the hood to play with the fuse... and I'll keep a charge on the battery.

Dale
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  #102  
Old 09-06-2016, 05:47 PM
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Quote:
Originally Posted by MrK454 View Post

So, the power to operate the power steering doesn't go through the 10-amp fuse circuit, but through the relay, which provides the power from the Jeep battery. I think I've finally got it.

Using my MH to provide power to the fused circuit will eliminate the need to install and remove the fuse, but the Jeep battery will still be at risk of discharge if the jeep isn't started to recharge the battery, or if a supplemental charge isn't applied to the battery. It should be a simple matter to use the same 12v+ source from the MH to power both the fused circuit and, with a diode, keep the battery charged.

Thanks again to all, especially to Array, who have pointed the way through this quagmire. I'll still use the switch inside the console, but I'll be freed from popping the hood to play with the fuse... and I'll keep a charge on the battery.

Dale
Thanks also from me to Array for giving the heads up on this modification. I've just done ours by simply removing the wire coming from the terminal under the fuse bay lid and splicing it into the wire coming from the MH into the RVi Toad Charger. I got a flat battery recently by forgetting to remove the fuse overnight. This mod will prevent that happening again.
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  #103  
Old 09-06-2016, 07:29 PM
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Re: 2014 Jeep Cherokee rv tow wobble

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Originally Posted by MartinC View Post
Thanks also from me to Array for giving the heads up on this modification. I've just done ours by simply removing the wire coming from the terminal under the fuse bay lid and splicing it into the wire coming from the MH into the RVi Toad Charger. I got a flat battery recently by forgetting to remove the fuse overnight. This mod will prevent that happening again.
Depending on how your coach is wired you may need to disconnect the umbilical cord when you park overnight with the Jeep still connected. On my coach that 12 volt source from the MH is only hot when the MH's ignition is on.

I would also like to thank Array and MrK454 for the idea and the information provided.
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  #104  
Old 09-06-2016, 08:50 PM
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Quote:
Originally Posted by BobGed View Post
Depending on how your coach is wired you may need to disconnect the umbilical cord when you park overnight with the Jeep still connected. On my coach that 12 volt source from the MH is only hot when the MH's ignition is on.

I would also like to thank Array and MrK454 for the idea and the information provided.
I think that's the beauty of this mod - the 12v source from the MH does go dead when parked thereby negating the need to remove the fuse.
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  #105  
Old 09-06-2016, 09:03 PM
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Re: 2014 Jeep Cherokee rv tow wobble

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Originally Posted by MartinC View Post
I think that's the beauty of this mod - the 12v source from the MH does go dead when parked thereby negating the need to remove the fuse.
My bad, you're absolutely correct. Had a friend that installed a switch and wound up with a dead battery when he left the switch on, however his power was still connected to the PDC.
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  #106  
Old 09-17-2016, 12:07 PM
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Re: 2014 Jeep Cherokee rv tow wobble

The following observation does not materially change anything, but worth adding to the conversation.

At the JCC site, klenger posted this: "In doing some research on EPS systems, I stumbled on a wiring diagram (not for a Jeep). On this drawing, the EPS main power is connected to the battery directly (not switched) and the switched power that the Jeep harness splices into is just a control line for the EPS. If the Jeep is wired this way, then the current draw on the control wire should be pretty low (the wire size is like 18 GA or so), but the load on the battery may be quite substantial when the EPS motor is providing significant torque, thus the need for a charge wire from the motorhome. Take this information for what it's worth as I am far from knowledgeable on this system. My real expertise is in aircraft avionics systems."

This makes more sense to me than the harness relay having 30 amp contacts and skinny wires carrying the current required to power the EPS motor. This suggests there might be a sizeable cable going from the battery positive terminal to the EPS motor; maybe similar to how the starter is cabled.

I was thinking about what Jeep could do going forward with this tow kit harness thing:

1) Change the front suspension and steering to eliminate the mechanical root cause of the shimmy while EPS power is turned off.

OR

2) Add the components during assembly that enable the EPS to be powered while ignition is off similar to the brake controller setup. The customer is responsible for purchasing their desired switch arrangement and plugging into the harness connector under dash. Dealer flash required to activate.
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  #107  
Old 10-27-2016, 06:11 PM
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Re: 2014 Jeep Cherokee rv tow wobble

How do I contact Kori @ Jeep cares? FMC declined my email and phone request for them to pick up the cost of the wiring kit and its installation. The local dealer also denied my request. FYI the 2015 Cherokee was purchased before the owners manual addendum was issued in 2016.
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  #108  
Old 10-27-2016, 06:22 PM
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Re: 2014 Jeep Cherokee rv tow wobble

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Originally Posted by dknewman View Post
How do I contact Kori @ Jeep cares?
JeepCares is a member account at Jeep Cherokee Club. Kori is one of the Jeep Social Care Specialists using that account. Her last post on this subject was here: Severe shaking problem towing behind motorhome - Page 54 - 2014+ Jeep Cherokee Forums
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