[[email protected]]

The Southco autopsy photos. View at your discretion. Yes......the guts are hanging out.

So, as a refresher, This latch failed when I opened the fuel door and the handle remained "pulled out". I ran to shut off the bay door power, but didn't get there fast enough. I then spent time spraying that door handle until it worked freely.
Subsequently, the mechanical release mechanism failed on this latch. The mechanical release on the other latch still worked.

Image #1 shows the latch with its cover removed. The latch has 3 main areas. The left portion is the mechanical latch with release capability and microswitch (more on this later) The center portion is the linear gear mechanism. The right portion is the motor portion. In this image, the release arm is clearly disconnected from its linkage to the latch. The latch linkage is a "U" shaped slot in the mechanical release lever of the latch. The microswitch on the latch is maintained  active when the latch is open. It has NO and NC wires available external to the whole assembly. The center linear gear mechanism is stuck in the half activated position. When the latch assembly is not energized, the spring would normally push the gear mechanism such that it would move all the way right, spinning the motor in reverse, in the process. The motor is coupled to the linear gear by a "bow tie" shaped coupling. The motor itself appears unremarkable in this photo, except that the rightmost margin area appears sooty and the adjacent nylon appears burned. 
Normally at rest while latched, the release arm is located in the slot of the latch release lever, the linear gear body is pushed all the way to the right, and the motor is at rest with no impressed voltage. When the latch is activated into the electrical release case,  a short 12VDC pulse is placed on the latch. This causes the motor to spin, moving the gear to the left, impacting the release lever, thereby causing the lever to rotate open and force the strike from its jaw. When the latch is activated into the mechanical release case, the gear and motor are irrelevant because the release arm pulls directly on the release lever, thereby directly causing the latch to open. Upon opening the latch assembly, the release arm was decoupled from the release lever, eliminating that method of release. The motor had also failed, eliminating any hope of that function.

Image #2 shows a closer view of the release arm and the slot in the release lever. It appears that the release arm is quite a bit thinner than the width of the release arm slot. It also appears that there is sufficient space between the top of the release lever slot and the adjacent wall of the latch assembly. This was probably the way that the release arm became uncoupled.

Image #3 shows the seized motor and the gear/spring not being able to push back.

Image #4 shows the melted right side of the motor. The rotor shaft uses the plastic housing as a bearing. Once gone, the motor does not move.

Image #5 shows the paddle/ "bowtie" used to couple the motor to the linear gear.

Image #6 shows the rating plate. Clearly, this device needs some sort of management of the voltage applied to it. It cannot be just connected to the bay handle switch. A quick flick of the handle will probably cause at least a quarter second of voltage to be applied. That is 5 times rating. This is why I say some sort of "one shot" circuit needs to be used. A "one shot" is used to control the length of the pulse applied, as well as to control the time to re-trigger. Additionally, the striker should be able to be removed directly from the bottom of a wedged-open bay door. In this way the latch would not be over stressed, electrically, and a way to overcome complete failure would be achieved. The microswitch is not rated, which means its not going to withstand use at a 5 amp rating, as the motor draws. If it was capable, the microswitch could have been used to cut off power while the latch was open.

Bob appreciate you tearing into this and analyzing the failure. This is how I learned how stuff works over the years, by just taking things apart. So if I understand what you are saying, the microswitch is not being used? I would take it that the microswitch is depressed when the latch is opened or closed? You could use the micro switch, would need to just run it to a relay to handle the load. I would assume that is why Southco put that microswitch in there, so that it could be used to stop the motor. Would be curious to see if one could find the installation information for those latches, I bet they have a suggested wiring diagram on how they should be used. 

As Richard said, great that you are contributing this information. I am sure it will help someone else some day.

[xGE_97]

Thanks guys. I'm pretty sure that Southco means it when they place that spec. The need is 50 ms maximum and a 450 ms minimum time between pulses. 

A relay can have an effective delay of 100ms while it is moving to make contact. That's twice as long as the spec. Any change should observe the maximum spec. Therefore a relay is out. The microswitch is activated after the motor has already moved the gear, so there is delay there, but not too bad. All that delay would have to be meaaured. And after that there would be variation because of mechanics, etc. If work goes into it, it should meet the goal. For me, a one shot does it because it controls how long the pulse lasts and when it can re-trigger. 

So the one shot would be "armed" and ready to fire a 50ms pulse (or shorter) at all times while the handle is released. Once the handle is picked, the pulse happens and will not be allowed again until the 12 volts goes away.... usually by letting go of the handle. One pulse only. And 50ms long. Want another pulse? let the handle go and pull it again. Like a semi-auto rifle. One bullet per pull. 

Newell service techs told me they've never used any wires from the latch besides the ones to activate the release. 

I don't think the one shot is over complicated. They use mercury switches in the doors to tell if a bay door is open. One of the uses is to disable slideout movement.

[Jack Houpe]

Great pictures and explanation! I had in my mind it was a solenoid not a small motor.

[[email protected]]

Thanks guys. I'm pretty sure that Southco means it when they place that spec. The need is 50 ms maximum and a 450 ms minimum time between pulses. 

A relay can have an effective delay of 100ms while it is moving to make contact. That's twice as long as the spec. Any change should observe the maximum spec. Therefore a relay is out. The microswitch is activated after the motor has already moved the gear, so there is delay there, but not too bad. All that delay would have to be meaaured. And after that there would be variation because of mechanics, etc. If work goes into it, it should meet the goal. For me, a one shot does it because it controls how long the pulse lasts and when it can re-trigger. 

So the one shot would be "armed" and ready to fire a 50ms pulse (or shorter) at all times while the handle is released. Once the handle is picked, the pulse happens and will not be allowed again until the 12 volts goes away.... usually by letting go of the handle. One pulse only. And 50ms long. Want another pulse? let the handle go and pull it again. Like a semi-auto rifle. One bullet per pull. 

Newell service techs told me they've never used any wires from the latch besides the ones to activate the release. 

I don't think the one shot is over complicated. They use mercury switches in the doors to tell if a bay door is open. One of the uses is to disable slideout movement.

I suspect you are on to something. I was looking for more info on that latch and could only find newer latches by Southco. The new ones lend a clue that they are designed to be operated by an electronic device to actuate them, so one would assume it has the one shot type of pulse output you speak of. Seems that the microswitch is really only there to confirm the position of the latch as a feedback or could be used for other purposes. They do mention a microprocessor but not sure where it’s located, and this may only be on the newer latches I was looking at.

[hypoxia]

Coach 1482 also has that Southco EM-03-43-340 latch.  Do you have the Southco number of the replacement latch?  Is it a direct replacement?
I checked with Southco, they still make that latch with a 4 month lead time.

That was excellent work you did and the information you posted is invaluable.

[Richard]

Hmmmmm, I have utilized these to keep my AC units from short cycling.

They are small, and have a ton of programming options.

https://www.amazon.com/Small-Timer-Delay...d_source=1

You can read the programming options here : https://timers.shop/assets/documentation...r_Wifi.pdf

Looks like you can pulse as low as 1/30 of a second or .033 sec or 33mS. Your 50mS requirement is within the programming of the relay.

I have used other timer boards from Amazon, but none had the flexibility, packaging or solid state relay that the timers above have. Also, the manuals for the other options were in Chinglish, very difficult for me to understand.

[xGE_97]

Hahahahahahahahahaha Chinglish hahahahahahahahahaha

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Jim,
I'm headed to Newell. When I get there I'll get the number of the new latches. These new latches have a cable instead of a release arm. There is anball on the end. Newell cuts off the ball and puts an extension on the cable. I'll get the number. I'd ask Creslie, but he's on his honeymoon. He gets back the day I get there!!! I'm surw I'm just the person he's looking for hahahahaha.

Really, Creslie is amazing. He is able to work through all kindsnof challenges and get the job done well.My hat's off to him.

[xGE_97]

Richard,
 Thanks. I don't have time to read it all at this moment, but I will. It looks like it could work. Ya just want to get a 50ms pulse followed bybat least 450ms before it re-triggers. 

At another time I'd like to talk about short cycling heat pumps.

And, Thank You, Thank You, Thank You for all your help inspecting my coach before I bought it!!! ( can't say it enough)

[Richard]

Bob,

Tell me EXACTLY how you want the device to function. Since it takes a wee bit to come up on the curve for the myriad of programming options, and I already had to climb that hill, and I will take a look at the options and recommend which of the programs and settings you may be able to use. My high school grammar teacher would kill me for that sentence.

For example, do you want it to pulse once? Pulse, wait, and pulse/wait over and over as long as you hold the button? Pulse, wait, pulse, wait, and stop after a specified number of cycles?

[Richard]

And to give you more to noodle while driving back to the mothership. There are a lot of devices used in home applications to keep the compressor from short cycling. The problem is that all of them are based upon 24VAC circuits used in houses. I could not get them to work on the 12VDC control systems used in RVs. I also could not find at the time a 12VDC tstat with built in short cycling protection.

Since I have two compressors per basement unit, and the tstat controls the internal fan and compressor on separate circuits, I used 4 of the above relays. I programmed them so that once the compressor gets a start signal, the relay will not close until five minutes after the compressor has stopped. I did the same for the internal fans. The programming has a little quirk in that it delays the compressor five additional minutes from the initial turn on.

Here is a pic of a spare board. The board is inserted between the tstat and the AC units. It is small enough that it was easy to hide close to the tstats.