quote:

Originally posted by MWrench:
...but the wiring diagram that I have clearly shows a on/off switch arrangement and not a latching system.

Myself, Rusty and Bill H could tell you that some engineers, builders or pencil pushers might have...
1) Taken a shortcut.
2) Didn't know any better.
3) Tried to save a buck.
4) Drew it on the plans wrong and the masses on the floor blindly followed.
5) Really felt that this was better.
6) Might have offered the other as an upgrade.

I'm invoking Rusty and Bill H names in here because anyone like them that's been around has come to the conclusion that blindly following the same thing over and over again doesn't lead to an answer...

It's the question I keep asking, I'm sure they say the same thing... we mumble within:
Hummm, that's odd, why did that fail?
and then we say:
There's got to be a better way!

I'm sure when my kids go to pack me off to the funny farm they will hear all my crazy talking I've done to myself.
Ps: Rusty is already there! Shields up!

I just spoke to a trailer supply company in hopes they could find the relay locally. Instead the owner argued that all trailers and RV's are wired with power constant to the relay that I have...and...why don't I just install a toggle switch to shutoff the power to the relay?..it doesn't draw that much power..He would have to investigate! I tried to tell him that by design the circuit was incorrect in function but he continued to argue. Anyway I just finished ordering the relay from Ecovantage on-line.

quote:

Originally posted by hilarlee:
I tried to tell him that by design the circuit was incorrect in function but he continued to argue.

You stuck to your ground. You know better now. I have this same problem when trying to straighten out engineers designs and HillBilly rigging.

He told you something like... I sell this other style all the time: Yes he does!

I like solutions, not reoccurring problems.

Bill NY

I understand your statement completely! My quoted comment was in response the question of if I had the coach since new, inferring that the relay system may have been changed from a latching style to an on/off style. It wasn't!

I am a EE by education and have spent 40 years or so designing UPS systems and AC power inverter/DC motor drives. I have been crew chief or lead mechanic on numerous racing teams and currently rebuild or refurbish older sports cars. (retirement hobby)

I am not defending Barth's decision to use a on/off relay system at all, it certainly wasn't the best way and as I mentioned I will be changing this system.

Since going thru my Barth, I have found quite a few things that I personally don't like the way those were either designed or implimented. The Barth's basic design is VERY good and a VERY GOOD platform to work with, and that is why I serached so long for the right Barth instead of a plastic and stick design.

One of the first things I do when there is a failure is do a failure analysis and implement corrective actions.

HTH

quote:

Originally posted by MWrench:
I have found quite a few things that I personally don't like the way those were either designed or implimented. The Barth's basic design is VERY good and a VERY GOOD platform to work with, and that is why I serached so long for the right Barth instead of a plastic and stick design.

One of the first things I do when there is a failure is do a failure analysis and implement corrective actions.

And you're a very smart man at that. Then you must know the level of incompetence and general lack of betterment that some mechanics seem to strive for. I want to know how everything works, and I don't mind looking like a dope if I learn something. I have no fear (except of the wife) of learning or teaching. I love my vocation.

I got a private email today and was told that his Barth was also wired like yours and hilarlee and asked if "maybe I might be mistaken". I thought about it some more and can't see where I fell off the track so I'm thinking it was on that list of 6 things that could have happened.

I even went to the Intellec website and found the spec sheet on that latching solenoid. They wire it a little (very little) different but it is the same reversing principle on the switch so I'll leave it alone in that respect.

The Email stated that his electrical knowledge "could fit into a thimble" but because he likes reading my postings didn't want to "embarrass you" (meaning me) but thought that I should know that you were right about the wiring diagram because "mine (meaning his coach) is like that too".

Why would someone have solar panels on a coach and then have a power draw for something as stupid as a constant duty solenoid? Why have a power draw at all when all it's doing is killing the batteries. It has to be a factory flub or a money saving thing. I don't know, but if I was there I would have made a strong argument for doing it like it's posted here.

We can arm people with knowledge and debate the merits of something. I love being proven wrong, It means that I learned something new. People like the way I can describe things over the phone and not sound like an "engineer" when describing something. You need to describe it like you're putting a picture into someone's mind, that way you usually see your own mistakes.

The trick is trying to sound like you're not talking down to people. That is the tough part because I don't know what anyone's background is. When I explain or respond to anything I make sure the maximum amount of people can benefit, even if some of what I say sounds basic to one person, Trust me, another one hasn't a clue. I love it when a light goes on in someone's head, it will help them out in the future I'm sure.

If I were a betting man (and I am not) I would say it is a cost thing, I am sure the latching relays cost more, an extra piece of wire, bla, bla bla, Bean counters do get their way and they were the biggest source of sleepless nights when I was a design engineer.

My solar panel charges even when the relay is off which is another thing that I don't like because charging technology and understanding of lead-acid battery technology in the late '80s/early '90s wasn't as good as it is today. I am looking into replacing the solar control panel with a later design that has better charging curves.

How about this one? I noticed in the Cummins manual that it says to check the harmonic damper for alignment, there are two marks, one on the hub and one on the damper, if more then 1/16 of an inch movement, replace the damper. So I look, spot on!, good! then I start the engine and look at the damper---holy cow--- did that thing wobble, almost 1/8 inch at the edge! well beyond the .035" the spec for wobble is. So I get a new damper---good grief--- the pulley for the main drive belt is attached to the damper ring and not the hub!!! So what that means is if the coach sits for a long period of time, the tension of the drive belt will put a constant compression on one spot on the damper isolation rubber and cock the damper.

Does Cummins see a lot of this, NO, but when they do, it is usually on low mileage RVs! Make one wonder doesn't it!

As I intend to use my Barth very often I am not worried about this issue but if I were going to let it sit for extended periods, I would change the damper to a fluid damper that is available (from Cummins for higher RPM operation)that has the pulley attached directly to the hub!

I believe we think alike Bill, I am also very curious about how things work and how they were designed, and of course many times I sit back and wonder-----WHY-----

HTH

Regarding the "Trailer Expert"'s suggestion to put in a toggle switch to shut off the the relay - what did that Bozo think the switch inside the coach does?

I think the use of a hot relay instead of a latching relay probably boiled down to "it's always been done this way!" in the days before solar panels, where a few ma of current weren't an issue.

My background is marine engineering (think EE/ME), and when I was an IG, I was tasked to determine why a landing craft's bow ramp hadn't been able to be raised, either by the motor or manually (the weather kicked up and the seas caused the ramp to break off). Here's an example of inertia....

I determined there were three issues:

1. The clutch on the ramp gear had failed
2. The manual raising mechanism (a gearbox and crank) operated through the clutch
3. The clutch failed because specs (prodcues by an engineer) called for the pads to be fastened with aluminum pop rivets (and they had failed due to creep and shear)

So I found the OinC and Craftmaster not culpable, and recommended that all craft be retrofitted with stainless steel pop rivets. For my troubles I was chastized by my admiral. As it turned out, his admiral had already decided to sack these two individuals ("Don't confuse me with facts!") A week later a Navy-wide FieldAlt went out to install the SS rivets. Total cost to the taxpayers, for all 600 vessels: $540. As it turned out (my admiral privately told me later) that the sheared rivets - never before all of 'em on one clutch - had been noticed and reported, and the aluminum rivets were still specified by engineering...

As to the crankshaft damper, my '81 Nissan Maxima 2.8L diesel had a similar arrangment - I used to replace it every 60K miles...

A final comment about engineers (exempting any on this forum, of course): The difference between an engineer and a technician is that an engineer can tell you how something works. He can't, however, tell you why it doesn't work.

quote:

Originally posted by Rusty:
The difference between an engineer and a technician is that an engineer can tell you how something works. He can't, however, tell you why it doesn't work.

My take is a little different:
The difference between an engineer and a technician is that an engineer can tell you how he thinks it should work.

The technician knows the engineer doesn't have to fix his mistakes, so the technician will have to re-engineer it.



A technician is the final quality control. He must be a "real world" engineer.

Of course, the real key for the engineer is to place the blame on the technician for failing to maintain the thing properly...

quote:

Originally posted by Rusty:
Of course, the real key for the engineer is to place the blame on the technician for failing to maintain the thing properly...

If he didn't how would he keep his job?

Well, as a fallback, there's always the Engineering and Design Committee....

quote:

Originally posted by MWrench:
How about this one? I noticed in the Cummins manual that it says to check the harmonic damper for alignment...

...if the coach sits for a long period of time, the tension of the drive belt will put a constant compression on one spot on the damper isolation rubber and cock the damper.

I would change the damper to a fluid damper...that has the pulley attached directly to the hub!

I am also very curious about how things work and how they were designed, and of course many times I sit back and wonder-----WHY-----

This slipped by me the other day but now I thought I would answer this.

Cummins will have you believe they do not see alot of this: On trucks, buses, motor homes I have seen these fail. The design with the pulley attached to the wrong side is a "flub" that has been around far too long.

Go out to your coach and place 3 marks on your harmonic balancer. Do it like you would for a triangle. Three marks at 3 points being equal.

Start up and shut down your coach 100 times. The marks will be in the same place 99 percent of the times. Really, I'm not kidding.

The belief that this is an isolated incident unique to motor homes is false. Just about every time you shut your coach off it stops at one of three places.

They stop because of the high compression ratio's of a diesel. I know this to be true for several reasons.

I have done it to figure out why the 8.3 Cummins has been going thru ring gears. The flywheel (ring gear) only wears out in one of three places. The ring gear is too weak.

When doing a diesel tune up you must manually crank over the engine. For my own help after I find #1 TDC I bar the motor over and find the next cylinder at TDC. I mark the crank, adjust valves and bar it over again adjusting valves and marking the next spot. After that the next 3 are in the same place so I don't have to waste time trying to line it up because it's already done.

Each time I shut off the engine the mark is always at the same spot. The motor always starts/stops in one of three spots.

The belief that because the motor will be run alot would work out well in a linehaul operation, but that's not going to happen in your coach. It will take longer to happen, but happen it will. Do yourself a favor and change to the one piece viscous style the next time around.

Sorry to be the bearer of bad news!

---------WHY---------
I just don't know what some engineers think. If you can figure it out let me know.
.

ARGH! I just completed the installation of the new Intellitech relay and DPDT switch. I ordered both part numbers suggested in this post and wired everything precisely as directed. I should mention that I used the 12VDC ceiling lights and turned them ON for test purposes. Immediately I noticed the ceiling lights stay ON. When I press the disconnect switch to the "OFF" position the first 10-15 times, nothing ut a clicking sound comes from the relay. Finally it disconnected 12VDC power to the interior of the coach and the ceiling light shut off.This worked for about 20 consecutive times. Double checked connections, final tightened the power leads to the relay. Went to test circuit-clicking noise from relay but no disconnect. I tested the switch in both positions and I measure 11.7VDC back at the relay on either switching post when the power switch is toggled on or off. Defective relay? Under rated relay? So far I have not been able to get the relay to disconnect. Any suggestions?

I just went to there website and pulled up the diagram for the Latching relay. It clearly shows the reversing aspect making and breaking and reversing power.

Check it out at

http://www.intellitec.com/PDF/5300066.100.pdf

Just so we don't leave anybody in suspense... The latching relay worked for about 20 times before failure. It worked with the switch as drawn out earlier in this post. The relay setup and diagram are correct, it did (past tense) work as described without additional power consumption.

Thrice-failed!

You can hear it latching and unlatching by reversing the current (different type of noise) but it is not releasing the latch. The new relay that they got has failed. It's rather depressing but stuff like this happens.

This is not the case on this installation but on an additional note: Sometimes a relay if they are tightened down too tight/uneven surface or the cable is pulled/cocked a relay can fail as well. Always be carefull on how tight you go with the cables and what a relay is mounted to.