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Old 06-24-2017, 10:19 PM   #1
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Another Step Thread

My new to me 2015 FR3 purchased by my wife and I less than a month ago, it had 24K miles.
Last weekend while working on the cab A/C, the steps stopped working. No noises, they just stopped. I took off the motor assembly, to find that the commutator was blackened, and the main gear (nylon) was damaged, presumably by the motor attempting to drive the steps down when the path was obstructed by a curb or something. I cleaned up the commutator with sandpaper, and filed the teeth.
I read the threads about putting a switch in place to stop the motor from running, so the steps would not be stopped by an obstacle and become jammed and damage the motor. I was concerned though, because knowing myself; I would drive off, sooner or later, with the steps deployed and locked down, and damage them big time.
So I came up with an idea. I would use a normally closed relay to control the power to the steps. The relay control coil would get its ground only when the emergency brake is on AND a switch added to the battery disconnect panel is closed. If I inadvertently leave the step relay switch closed, and try to drive away, releasing the emergency brake will remove the ground from the relay winding, and the relay reverts to its normally closed condition and the steps retract.
I found the best and closest place for emergency brake-controlled ground at the Lippert Leveling Control connector. The power input plug only has two wires, red power and white ground (only grounded when the emergency brake is on. I tapped into the white wire, soldering a wire running across the underside of the motor home to the Coach Battery Compartment, and up into the battery disconnect switch at the top of the interior stairwell.
I inserted the n.c. relay at the green fused wire providing power to the step system.
I can lock the steps in the up or down position, but they will retract as normal when the emergency brake is released.
I am enclosing some pictures and a rough wiring diagram. Click image for larger version

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2015 fr3 30DS, added 2nd A/C-Heat Pump, converted to 50amp, CHF with Hellwig Links, Progressive Power Management, TPMS, Blue Ox True-Center, Koni Shocks, HID Headlamps, LED Foglamps, Pioneer Stereo, Keyless entry, Auxiliary Cooling Fans for A/C Condenser.
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Old 06-27-2017, 10:49 AM   #2
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I like the way you think Hogq, from another EE mind. Great mod!
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2015 FR3 30DS
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Old 06-27-2017, 11:31 AM   #3
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The steps motor stopping is controlled by current increase to a cutoff level. Every time the steps extend/retract and reach their maximum mechanical travel stop it's the current increase that shuts the motor off. It's the same when an obstruction does not allow the steps to extend/retract fully. This is all normal operation of the steps. Sounds like your control module or motor has an issue. Electric windows in a car do not have travel stop switches.
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Old 06-27-2017, 12:32 PM   #4
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Quote:
Originally Posted by bubbles View Post
The steps motor stopping is controlled by current increase to a cutoff level. Every time the steps extend/retract and reach their maximum mechanical travel stop it's the current increase that shuts the motor off. It's the same when an obstruction does not allow the steps to extend/retract fully. This is all normal operation of the steps. Sounds like your control module or motor has an issue. Electric windows in a car do not have travel stop switches.


Yes, I agree. I don't know what the current threshold is. It is high enough that over time the brush material fused to the commutator. The biggest functional problem was that the nylon main gear, had lost tooth material into the grooves. I cleaned that up.
The main reason for my mod, was to reduce the cycles on the step motor, and keep the motor from going into lock-rotor, without need. At the same time I wanted a fail safe method to limit the step operation (and thereby lock them in or out) so my mod did not override the intrinsic safety of having the steps retract upon door close/engine running.
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2015 fr3 30DS, added 2nd A/C-Heat Pump, converted to 50amp, CHF with Hellwig Links, Progressive Power Management, TPMS, Blue Ox True-Center, Koni Shocks, HID Headlamps, LED Foglamps, Pioneer Stereo, Keyless entry, Auxiliary Cooling Fans for A/C Condenser.
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Old 06-28-2017, 01:13 AM   #5
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The intrinsic safety factor is that the steps "extend" whenever the door is opened no matter ignition and/or step power switch position. Just a thought. if what you did works for you then that's all that matters.
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Old 06-28-2017, 07:59 PM   #6
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safety

The steps on my FR3 do not lock unless they fully extend. There is an adjustment for the extend-lock. I noticed they are decidedly unstable when unlocked.
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