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Old 06-05-2017, 11:11 AM   #1
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Strange steps action

Hello,

I am new to the forum, but have search for a clue to my problem before posting my question.

I have a 2014 FR3. I am plugged into shore power(my house), and have the "Step" switch in the position which keeps the steps down when the door is closed. Here's my problem. As part of my spring checkout, I ran the air conditioner. Occasionally, when the air conditioner compressor comes on, the steps will retract. I have checked all fuses and breakers I can find associated with the air conditioner and the steps, but all seam ok. It's repeatable as far as the steps will eventually retract.

Confused,
AlbertFR3
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Old 06-05-2017, 07:45 PM   #2
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I'm assuming the A/C you are running is the roof A/C and NOT the engine A/C. Because, if the engine is running, the 'out stair lock' is overridden by the engine on and the stairs retract (with the door closed). I believe all of the 2014 FR3s are 30 Amp and that when you say plugged into the house, it is a 30 Amp circuit. Also assuming this is a new problem meaning something broke or degraded.

The roof A/C operates on 120VAC (except for a small amount of 12VDC for control) and the stairs are on the 12VDC system - very separate. So, you have a strange issue. It's not likely a fuse or breaker because it's intermittent.

What comes to mind is a voltage drop in either the 120VAC or 12VDC (via the converter) when the A/C compressor starts up (when it uses its max current). Somehow, the stair logic thinks you've switched off the stair lock out or that the engine is on. Either of these 12VDC signals could be miss-interpreted by the stair logic if their voltages are affected. A loose wire could be to blame for these two signals, as well, a loose ground on the stair system could cause issues. I'd check the stair wiring including the green chassis ground wire.

Also coming to mind are weak batteries or your master power switch is off (leaving only voltage from the converter which might be lowered with low VAC power).

Once retracted, do the stairs stay in or do they redeploy after the compressor has completed starting or stops?

You can isolate the problem to the lock out switch (and wiring and logic) by leaving the door open during your test. If it still retracts, it's not the lock out switch.

If I try to write a logic statement: (IF the door is open THEN extend the stairs ELSE (IF engine is on THEN retract the stairs ELSE (IF door is closed AND lock out switch is off THEN retract the stairs ELSE leave stairs extended)))

There's a remote possibility that as your A/C compressor is getting older, it requires more start up current and is not only creating lower voltages, it's also throwing noise on the wiring and through the air (electromagnetic fields) that are notorious for causing logic issues.

You might also try to do your test with the on board generator to see if it's a 120 VAC feed issue.

Hope this helps.
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Old 06-06-2017, 06:10 PM   #3
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Kadiddle, good thinking! TY for sharing. Share more in the future!
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Old 06-07-2017, 07:19 AM   #4
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Hello Kadiddle,

Thanks for the detailed explanation. It appears the problem was a drop in the 115 vac, to below 104 vac. I have a hard wired Progressive Industries input power protection module, which indicated a low voltage error. I have used this setup for the last three years, without a problem. I confirmed the problem by using the on board generator without any issues. The house outlet I used is a 15 amp circuit. Since I bring the FR3 home each spring and fall for winterization/de-winterization, I will probably use the on board generator for the air conditioner checkout.

Thanks again for the troubleshooting tips.

AlbertFR3
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Old 06-07-2017, 08:41 AM   #5
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Your welcome. I'm an electrical engineer but spent most of my career as a "systems engineer" and project lead. The hardest part about troubleshooting electrical systems is when something is marginal. Clearly broken is easy.

Using a 15 AMP house circuit for the A/C in your coach is NOT a good idea. You might get away with a 20 AMP circuit (be sure to use at least 12ga wire including extension cords) as long as the A/C is the only 120VAC load in the MH. I recently moved to a new house and had the builder put a 30 AMP RV connector on the side of the house. Love it!
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Old 06-07-2017, 09:09 AM   #6
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Quote:
Originally Posted by AlbertFR3 View Post
Hello Kadiddle,

Thanks for the detailed explanation. It appears the problem was a drop in the 115 vac, to below 104 vac. I have a hard wired Progressive Industries input power protection module, which indicated a low voltage error. I have used this setup for the last three years, without a problem. I confirmed the problem by using the on board generator without any issues. The house outlet I used is a 15 amp circuit. Since I bring the FR3 home each spring and fall for winterization/de-winterization, I will probably use the on board generator for the air conditioner checkout.

Thanks again for the troubleshooting tips.

AlbertFR3
The AC power can drop to zero and the steps will continue to operate normally. The steps are 100% DC power fused directly off the battery. The ignition interlock input is a +12volt input. The step "switch" power is from the battery control center via a fuse and that input is needed to keep the steps extended when the door is closed. Did the light go out in the steps switch when the anomaly occurred? A drop in battery voltage would render the steps inoperable. I don't have any idea as to what caused your issue but doesn't seem like any AC power issue will cause it. JMO.
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Old 06-07-2017, 09:41 AM   #7
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bubbles,

I totally agree with your observations. At first glance, I'm also thinking about how the 120VAC and 12VDC circuits are separate systems. However, AlbertFR3 was having a direct correlation between the 120VAC A/C compressor cycling and the actions of the 12VDC stairs. Surprising but hard to ignore. This led me to bring up some of the weird ways the two could be related.

Integrated Circuit technology these days is so various, it's hard to say what sort of logic (CMOS, JFET, MOSFET, LVTTL, ASIC, FPGA, etc.) is in the stair system's brain. But easy to say it's sensitive to voltage levels and short transients (spikes). So, weird things can happen.
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Old 06-09-2017, 01:15 PM   #8
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Are perchance the 12vdc coming from the onboard charging syetem? Or batteries getting low/used up to the point thwt when the charing 120VAC system drops the charge to the batteries drops and the stairs retract.

Just asking as it does seem the two are related and the common point between the 12vdc and 120vac would be the charging system.

But hey at least they are only retracting....lost a set due to opening while in motion. Turns out the magnet on the screen door was not aligned with the sensor on the frame. Left a lower step at a curb near a walmart in GA one day.
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Old 06-10-2017, 07:33 AM   #9
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KY25DS,

Sorry to hear of your stair loss. I guess the safety of absolutely making sure the stairs are out if the door is open overrides everything even at the expense of the stairs in failure modes. During my career, designing systems with a series of safety interlocks and understand what happens in various failure conditions was always challenging.

Not for reasons of stopping the stairs from deploying when the switch fails (or is mis-aligned), I put a bypass switch around the door magnet switch. I did it so I could force the stairs in with the door open. So, if I'm parked at a curb or other obstruction, the stairs would not deploy and be damaged. I also found that when loading up the MH, I could keep the stairs in, walk up right to the side of the coach, and pass items up to the DW inside. (And it actually takes two switches to be in the right position just to make it harder for anyone to accidentally retract the stairs while standing on them.)

Regarding the link between the 120 VAC and 12 VDC systems, you are absolutely correct about the link through the converter. If the 120 VAC side is perturbed by low voltage or power spikes/noise, that could easily affect the 12 VDC output, with or without the batteries, and confuse the stair logic. 120 VAC compressor (an inductive load) start ups cause not only a drop in voltage but also lots of spikes/noise on the power lines. I wish we knew exactly what caused the OPs stairs to retract. A strange experience, no doubt. A lesson for all of us.
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Old 06-10-2017, 11:03 AM   #10
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Investigation continues,

So the rig is currently at my outdoor storage facility. But tomorrow I will be bringing it back home and continue the stair retraction investigation. I plan on duplicating the same conditions as before, and get the same stair retraction as before. Once I confirm the problem, I plan on disconnecting the inverter and see what effect that has. Any other suggestions are appreciated.

AlbertFR3
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