Locking Out Rubicon Sway Bar with Relays - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 5 Old 04-04-2018, 11:41 PM Thread Starter
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Locking Out Rubicon Sway Bar with Relays

It finally hit me a few days ago how easy it should be to make the Rubicon sway bar stay unlocked no matter what, 2Hi, on the highway, whatever.

The sway bar requires power to lock, or to unlock. This is not like an E-Locker where you have to constantly supply power to keep it going. Only needs power to lock when unlocked, or to unlock when locked (at least I'm 99% sure this is true).



Just put a normally-closed relay on B. Put your Jeep in to 4Hi, unlock the sway bar, then activate the relay and the sway bar no longer has power. No matter what you do, it shouldn't re-lock.

But, I tried it tonight and when I turned off the relay the sway bar made its motor noise for 2 seconds and it was locked again.

Ok, so I figured they put in some safety redundancy and I have to also simultaneously cut B1.

So I hooked up another relay to B1 and repeated the experiment simultaneously cutting power to B and B1. Again, a moment later the motor activated and it re-locked.

What??? Does anyone understand how this is possible? All it has is GND and CAN, there's no power source remaining. Is there something absolutely stupid where Chrysler was so scared of a law suit that they didn't consider double redundant power sufficient and put a little battery inside the sway bar? Hard to believe that'd be the case, but where else is it getting power?

I was 99% sure this was going to work and it did not Any ideas on what could possibly be going on here? The electrical unit is pretty much sealed on the sway bar so I don't really want to go cutting into it. Anyone ever taken one apart and seen either huge capacitors to store enough power to run the motor for a few seconds, or a small battery?
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post #2 of 5 Old 04-05-2018, 04:49 AM
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As the sway bar unlocks, the electric motor winds up a clock spring. Once unlocked, power to the motor is cut, but a brake on the motor is energized.
When power is lost for any reason, the brake releases, and the clock spring unwinds, driving everything back to the locked position.

2008 Unlimited Rubicon Automatic
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post #3 of 5 Old 04-05-2018, 08:46 AM Thread Starter
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Quote:
Originally Posted by ronjenx View Post
As the sway bar unlocks, the electric motor winds up a clock spring. Once unlocked, power to the motor is cut, but a brake on the motor is energized.
When power is lost for any reason, the brake releases, and the clock spring unwinds, driving everything back to the locked position.
Hmmm, dug deeper into research and found discussion of something like this.

But then there's this guy who got his to work by applying power only to change states:

I wonder how if there's a spring-return and a brake that has to carry current to stay unlocked...
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post #4 of 5 Old 04-05-2018, 03:46 PM
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Quote:
Originally Posted by christensent View Post

But then there's this guy who got his to work by applying power only to change states:
I wonder how if there's a spring-return and a brake that has to carry current to stay unlocked...
I don't know what he may have done to his sway bar, but yours is behaving exactly like it's set up as described in my post.

I'm waiting for my sway bar to fail so I can install the one I converted to lever operation from the cab.

2008 Unlimited Rubicon Automatic

Last edited by ronjenx; 04-05-2018 at 04:35 PM.
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post #5 of 5 Old 04-05-2018, 07:02 PM Thread Starter
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Quote:
Originally Posted by ronjenx View Post
I don't know what he may have done to his sway bar, but yours is behaving exactly like it's set up as described in my post.

I'm waiting for my sway bar to fail so I can install the one I converted to lever operation from the cab.
Ya, it looks like it definitely is as you described. I think I'll take it apart and see if I can just take out the return spring and then maybe my relay trick will work. Not sure if it motors return or just uses the spring in which case it wouldn't work anymore, but the whole 18MPH thing is driving me absolutely crazy so if it doesn't work out I'll do something else in the end.
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