Single point failure

Upon departing the Lake Havasu rally, we headed south to a wildlife refuge along the Colorado river. We always lock the coach with the key fob remote. When we came back, the door would not unlock. Oops, now what?

Our coach has a Trekmate alarm system which controls the door lock. Trek Mate is out of business. Somehow, the alarm could no longer communicate with the fob.

I had the keys, and could get into the bays, but that was all. Called Marathon and Prevost for advice, they could not solve the problem. They suggested relieving all the air pressure from the auxiliary system by draining the fittings at the rear and below the driver seat compartment. No luck. The lock would not open.

So, we removed a side window. Flipped the button by the door both ways and it popped open. Then it started to rain.

Put the window mostly back in ( even though it had a crack now) and spent the night. Next morning finished putting it in on a bright sunshiny morning.

Prevost gets $500 a piece for those side windows, only $175 for a windshield. Amazing. I will replace it again after we get home with a new one.

So, what we need is a back up plan in case the fob does not work. I plan to wire in a parallel switch accessible from below the driver seat compartment, which will activate the lock the same way that the alarm does.

I do not want to go through this again!

One must be aware of all the little tiny things that can bite you when you are not paying attention......

All's well that ends well, I guess. I can imagine the panic (I would have had). And you should be ashamed at the language you used.

Put your entry door key in one of those cheap little magnetic boxes that says "spare key" and position it secretly in the engine compartment if unlocked or under the front bumper (like me).

You can continue to carry the remote Fob with you and if it fails to work - you have a back up plan.

Without a pocketful of keys.

Experience is the best teacher I know.

I carry a entry key with my Fob. Peter, do you have a seperate entry key?
Maybe you can install a new system with a key pad as well.

I don't know if this applies, but wasn't their a thread recently about a similar incident (i.e. being locked out), and the solution was to open the engine bay and turn off the 12 and 24v house batteries, thereby resetting the stuff internally and opening the door?

Am I remembering this wrong?

Ray

Our key fob works in concert with our Ford style combination lock keypad, both of which engage the solenoid operated dead bolt on the Corbin lock.

I don't know of any locking systems that engage the air lock from outside the coach. The simple answer as Roger suggested is keep a key outside that can be accessed. Everyone should probably give some thought to their locking system. It is far better to understand how it works and the scope of the security features before it malfunctions in some remote KOA.

Some not only lock the door, but they disable the engine by shutting off the fuel supply. Simply getting in the coach by unlocking the dead bolt may just be part of what has to be done to be able to use the coach. You may have to also have a plan to make sure the engine fuel supply has not been interrupted by the security system.

But going beyond that, Peter labeled this topic "Single Point Failure" and I think it is a good exercise for pilots and Prevost drivers to go through a "what if" scenario regarding all the systems and features. Here are some single point failure items that might inspire someone to deal with before the failure becomes a serious problem.

Water pump......if you have one pump, and it fails, and you are on the road you will be using public rest rooms. That was my inspiration to add a second pump.

Inverter..........unless your coach has a way of by-passing a failed inverter you may not get electric to critical components like your refrigerator even if the generator is running or you have shore power

Alternator.......regardless of whether you have one or two, if one fails you need a way of charging the circuit. If it is the house, run the generator and the inverters will do the job. If it is the chassis, do you have a chassis battery charger?

Generator........Probably will not be an issue as long as the chassis alternator(s) work or you can get to shore power. But what if you need it to run your ACs?

Air bags, brake chambers, belts, hoses, etc.....Do you have spares or are you replacing those parts as preventive maintenance?

Relays, circuit breakers, switches, fuses........There are more items that rely on simple parts such as a relay than can be listed here. Everything from lighting, starting, and running depends on relays and circuit breakers and switches. It never hurts to carry spares. If you have no spares it is a great idea to know which relays, fuses or switches you can substitute for a failed one. I would not hesitate to switch a circuit breaker for a Jake brake to replace a bad one on the DDEC circuit.

None of us has or will experience every single point failure possible on our coaches, but with a little thought we can identify those failure points that are really going to screw us up, and develop a plan on dealing with it. We can also recognize some failures that will need a plan, but are so easily resolved it is not worth doing anything to deal with them. Just having the plan however is dealing with the problem.

Hello again. Just a couple of clarifications:

1. Rfoster, as I mentioned in my original post, I had the keys in my hand. And I also have a spare hidden away for outside access.

2. GaryDe and Rfoster, the Marathon system does not use a key to unlock the door if locked with the fob. other converters may well be different. My point in posting this is that everyone should be aware how their individual coach is set up.

3. Ray Davis, you are right, and Marathon and Prevost both suggested that method of removing electrical power, which I tried, it did not work. Sorry I forgot to mention that because that is another reason this problem can be such a pain.

4. Jon, your Liberty is different, note below. And your other points are on the money. We try to prepare for eventualities, but can not possibly cover them all. I posted this problem mostly because there are many Marathon conversions and owners should be aware of this particular glitch.


My Marathon entry door has 3 "locks".

One has no key and is the latching mechanism operated by the handles on the inside and outside of the door. It grabs the pin sticking out into the doorway on the left side as you enter and clicks the door closed when you slam it. (Once upon a time this mechanism broke inside the door and we were trapped inside, since all my tools were in the bay. I now carry a phillips screwdriver and 2 allen wrenches inside the coach to remove the inside door skin to access the mechanism.)

The second lock is a deadbolt in the door, operated by a key on the outside and a finger latch on the inside.

The third lock is an electrically controlled but air operated latch mounted on the coach body door jamb. This is controlled by the switche next to the door, switch on the dash by the driver, and in our case, by the key fob from the alarm system. We always latch the door when driving with this lock, and have always until now used it when we leave the coach. This is the lock that would not open. Removing air and/or electricity had no affect on the lock, except when we turned off all the electricity the alarm siren began to sound. it is apparently wired directly to the batteries and may explain a very small current drain even if the batteries are disconnected ( 35 milliamps according to the alarm manual).

So to sum up, I plan to install another switch, accessible from the outside, to unlock this third lock in case of fob failure in the future. (I was able to reprogram my fob, and the alarm and fob work correctly again.)

I sincerely hope this thread helps at least one reader avoid this problem in the future.

Peter: it would be interesting to hear what your converter has to say about the jackpot they have left all their customers in. Our old royale used to play tricks on us by locking itself, but a key from the outside would overcome the problem.This is serious non operator caused problems we all should be prepared for. i'm adding a allen wrench set to my screwdriver stash inside the coach. Thanks

Ray, I think you are thinking of this thread;

http://forum.prevostownersgroup.com/...ead.php?t=2250

Very similar, but not the same issues.

JIM

Peter
do you think the FOB was the problem? Could something have happened to it while you were out walking around like some electrical signal de-programed it "for" you. Hence it would not work on your alarm system again.
GregM

I remember when we purchased our 93 CC, I spoke with the previous owner about the alarm system function. He told me he had the door lock feature disabled (pulled a wire off of the controller) because it had a habit of locking him out.

I've left it that way and lock with the dead bolt when away, use the air lock while traveling. We only have the two!

Mike

Jim, that was an interesting thread, it is a similar problem. Greg, you are probably right, the fob was deprogrammed from the mother alarm. I was able to reprogram it, and it acted like a new fob, rather than finding an old fob again so the problem could have been with the fob or the brain.

A backup/bypass switch is the answer if you have a system built this way.

Peter, was the horn a simple fix?

The horn began going off randomly, not connected to turning the wheel or bumps in the road. it became embarrassing while pulling in and out of the Lake Havasu RV park, other buses started answering the horn calls even. When we left it was on more than it was off.

The horn was simply disabled by removing the wire that leads to the steering column under the flexible rubber part near your knees. The final repair will happen later.

Katherine says it was like the bus had an extreme case of flatulence without the smell!

Quote:

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Originally Posted by JIM CHALOUPKA

Ray, I think you are thinking of this thread;

http://forum.prevostownersgroup.com/...ead.php?t=2250

Very similar, but not the same issues.

JIM

---

In that thread: ....... In case you had a monkey or child, you could remove the key. :D

Is it possible to discern which?

Single Point Failure, no more.

Project completed, now there is a back up. Here is the full story.

In the door jamb there is an electrically controlled air cylinder which engages the door and locks it closed when power ( 24 volts) is applied to the solenoid that is attached to the air cylinder. This power comes from either the switch on the dash by the steering wheel, the switch next to the door, or in the case of my Marathon, from the alarm system. If the key fob is used to lock the door, it causes the alarm system to send power to the solenoid and the door locks.

In the case of my problem, the key fob would not unlock the door because it somhow became unprogrammed from the alarm brain. Obviously the same problem would exist if you lost the fob, for example.

Marathon suggested relieving the air pressure from the auxiliary air system, they thought that if there was no pressure, the door would open. But that is not the case, because the solenoid traps pressurized air and keeps the lock locked. You must remove the power from the solenoid to open the lock. They also suggested turning off the 2 chassis battery switches on the right side of the engine bay to kill the power but that did not work either. It would have worked if, say, a dog had pushed the switch by the door while the people were outside.

The lock system was installed by Prevost, but Marathon added the alarm system. And they power the alarm from either the house or chassis batteries directly, if you turn off the 4 main disconnect switches in the engine bay, the alarm is still powered. If I had disconnected the battery cables completely, the lock would have opened. Too bad Marathon or Prevost did not explain that option, but when it is getting dark, about to rain, and no tow car; it is easy to claim the sure answer and remove a window.

Today I spent an hour running 2 wires from the door lock cylinder over the top of the windshields and down into the electrical bay under the drivers window. There is now a switch there which is always in the ON position. If I ever have a problem again, I need only flip the switch to off and the lock will open. I thought this was faster than tracing the wires and finding the source of power to the alarm, and it provided back up to the 2 direct switches as well.

Nice to have one permanent solution.

Am I missing something Peter? Couldn't you just kill the battery power switches to the bus and house to accomplish the same thing?

Jon,
Of course I tried killing both the chassis and house battery switches, but that did not work. Marathon wired the alarm direct to the battery avoiding those switches. I wish they had told me that. I could have unbolted all the battery cables had i known.

Don't be too harsh on Marathon.

On my Liberty my CB power comes direct from the batteries in the rear and turning off the house battery switches does not kill power to the CB. I guess each converter has its oddities.

I would venture a guess that in general you don't want something obvious to completely defeat your alarm system, like turning off the power switches?

Granted generally the switches are behind a locked bay or engine door, but still, I'm guessing that is the reason.

Ray

It might be the case that some owners would want to park their bus, and turn off the master switches, while retaining the ability to lock and alarm the bus with the fob.

What I think is the bad part of Peters incident is that Marathon tech people DIDN'T KNOW HOW THEIR PRODUCT WAS MADE, OR HOW TO ADDRESS THE PROBLEM.

Jon, radio transmitters are supposed to be connected directly to the battery terminals with a fuse in both the positive and negative lines. It is the SOP. I will put it on my list of things to do to find out more, unless someone else chimes in. Ray, Warren, Jim S, Mike K, any of you know?

I don't remember exactly why, something to do with safety and radio interference, I think. I don't think the safety is a very big part with the low power CB rig, but a manufacturer must follow accepted practice to avoid the liability issue.


JIM

My CB is connected to the Coach Batteries. There are severall yellow wires attached to the Chasis batteries but I believe they are to the Detroit.

Jim, you are exactly right. I am satisfied with how Marathon built it all, I am just unhappy that when I was locked out and called their 24 hour emergency tech help line, that they were not knowledgeable enough to tell me what to do.

I learned the old fashioned way, by experience. And I hope the rest of POG can learn from my experience rather than having to fork over $500 for a needlessly broken window.

Since we are reading about the most recent door latch failure and with there being many new members that are unaware of past discussions on the door latch and similar/related incidents I am pinging this thread for a re-read by those interested.
Note that on post # 15, there is a link to yet another related episode in the ongoing saga "a little maintenance for the 1,000,000 mile vehicle".

Gee that number doesn't seem so big anymore compared to the numbers coming out of Washington:eek:


JIM