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Author Topic: Leavin' the "Engine Run" switch on (?)  (Read 2134 times)
WEC4104
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« on: May 27, 2007, 03:22:42 PM »

On my 4104, the previous owner had set up a switch and solenoid to connect the house and engine battery systems together, if desired. Normally, with the switch in it's home position (labeled "Single"), the two battery systems are separated. When the swirch is placed in the "Dual" position, and ONLY when the Engine Run switch is in the on position, the two battery systems are joined.

I should note that my 4104 has been converted to a standard 12 volt negative ground set-up.

When I am plugged into shore power, my converter always keeps my deep cell house battery nicely charged. However, I am running into issues with my engine battery system. I have 4 John Deere Strong Box 6 volt batteries in parallel & series to create my 12 volts.

While I sort through some problems with the enigine system not being charged, there are times when the "Dual" switch has made the difference in my being able to start the engine. I either have bad battery cables, weak batteries, or a phantom battery drain, because I am showing about 10.7 to 11 volts on the dash gauge, if the engine isn't running.

This brings me to my question:  If I were to leave the battery switch in the Dual position, and turn the "Engine Run" switch to on, the converter would be charging both battery systems. I have never left the bus sitting for an extended time with the engine switch on, and don't know if this would cause any other problems. On a normal car (pre electronic ignition) I was told you could burn up the ignition points. Obviously that doesn't apply for ol' 2 stroke diesels.

I suspect there would be some battery drain in that position, but if the converter is putting in more amps than the drain, the net result will be positive. 

Anybody see a down side to leaving the 4104's engine run switch turned on if I need to charge the engine batteries?
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Dallas
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« Reply #1 on: May 27, 2007, 03:58:23 PM »

If the engine run switch is left in the on position and the air drops to less than 60 psi, you are going to be hearing buzzers and seeing lights on the dash board. You'll also have a low oil pressure light and a no charge light glaring at you.

Also while the switch is in the on position, your regulator will be engergized along with various relays. This probably isn't a good thing as you may cause premature burning of the points in the relays.

Wouldn't it be easier to remove the wiring for the isolator from the ignition and wire it directly to your start batteries? You could also get fancy and put in 2 LED's, a red one for start batteries and an amber one for combined.

I would figure out your charging system problem before I did anything, it's possible that the wiring is already screwed up and once that's fixed you won't have a problem anymore.

IHTH,

Dallas
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WEC4104
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« Reply #2 on: May 27, 2007, 06:25:11 PM »

Dallas:

I'll be the first to admit this is putting a Band-aid on the situation, and what I really need to do is fix the root cause. But while I sort things out, it would be nice to know whether leaving the Engine Run switch in the on position is an option to bail me out of a dead battery situation.

I have low air and low oil pressure tell tales on the dash, but no audible signal. If I had to leave the dash lit up like a Christmas tree for an hour or two, that really is no problem.  I understand that turning on the Engine Run switch activates some relays, but don't these same relays stay activated for hours at a time as the bus cruises down the interstate? I'm trying to understand the difference.

I agree that rewiring things so that I have the option to charge the start battery independently is the best way to go. But if I can hit a switch or two and do the same without damaging anything, that presents a quick short term option.

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Dallas
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« Reply #3 on: May 27, 2007, 07:04:02 PM »

I'll be the first to say I'm not 100% certain that leaving the switch on will hurt anything.

I do know however, that the points in the regulator are built to make and break over and over again. this helps in keeping them cool.
I burnt out a regulator on my 63 ford one time by leaving the switch on for an extended period of time. (I was using the car generator to power some lights we were using to repair some equipment in the woods, we went to eat and it ran out of gas, we also got sidetracked having to chase parts, and 7 hours later, we were back, the car was out of gas, the battery was dead and the regulator was fried).

As expensive as the carbon pile regulator in your 4104 is, I'd be careful in how I treated it.

If you still have a rectifier in the system, and I'm not sure you do because it's been changed to negative ground and you have no buzzers now, it will also heat up.

In my bus if I leave the ignition on, I can hear a relay kick in and out every 30 seconds or so, I'm not certain what it goes to, but it does draw beaucoux amperage - my amp gauge will go from -5a to -40a everytime it cycles. I haven't bothered to figure out what it goes to yet, I just turn the switch off. I guess I'm just too lazy to fix it.

What you might do is install a temporary ammeter then turn on the switch and watch to see how many amps you're drawing. If the draw is more than your charger can supply, you won't do any good by leaving the switch in the dual position and the ignition on.

Just trying to help and keep you from burning anything out. It's no fun trying to figure out 50 year old wiring on a asphalt parkinglot.

Dallas

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Don4107
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« Reply #4 on: May 27, 2007, 08:35:26 PM »

Best bet would be to have the start battery bank teated. 

Redneck load test.... Disconnect the start batteries and charge them.  Let it set a few days after you charge them.  Put the cable back on and try starting it. If they are still weak you most likely need batteries.  If its starts well, kill it and turn on your headlights for about 15 minutes.  If it still starts well batts might be OK.  If not they are weak.  Assuming starter and cabling is good.

If the batteries check out then you need to make sure you engine driven charging system is up to snuff.  Your volt meter should increase to near 14 volts or more when the engine is running, assuming the meter is accurate.  Hint, some automotive volt meters are intentionally miss calibrated because people expect to see 12 volts, not the true 14 volts or so on a "12 volt' system.  Check it with a multimeter to be sure.  Another hint, if the batteries appear to reach full voltage/charge quickly after seeming to be drained they have lost their capacity, also know as only taking a surface charge.  (Reason for the headlight test)

Redneck charging system test.... turn on the headlights with engine off at night.  Start engine.  If head lights get brighter with engine running and/or revved up, the charging system has at least some output.

Then you should  look for what is draining them over time if the batts and charging system check out.

Useless info, I have over the years had more grief, less longevity, with battery banks made up of multiple batteries using 6 volt batteries in series than just using 12 volt batteries.  In your system the start batteries are only as good as the weakest cell.  While this is true using 12 volt batts, it just seems to me that 6 volts cause more trouble.  If for no other reason there are more connections to maintain.  Exception was a pair of much neglected golf cart batts I used in one bank of my boat.  Can also be harder to get fresh 6 volts.  Used to handle batteries in farm country.  Had noticeably more warranty issues with 6 volts.  But then the equipment tends to sit for long periods too.   Of course I might be all wet, being a redneck boater as well as a busnut.

Good luck finding you problem.
« Last Edit: May 28, 2007, 12:43:26 AM by Don4107 » Logged

Don 4107 Eastern Washington
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Gary '79 5C
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« Reply #5 on: May 28, 2007, 05:07:49 AM »

Don4107,
Love your "red neck charging syst. test" LOL...
Great stuff much because it is the simplest and many times it is the simplest reasons the charging systems fail. I agree with the multiple 6V batts.
Have a Great Day,
Gary
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John Z
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« Reply #6 on: May 28, 2007, 07:51:51 AM »

Back to your original post - if what you want to do is have the batteries linked while sitting, why not just energise your relay/solenoid/isolator from the house bank, rather than the start batteries?
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Don4107
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« Reply #7 on: May 28, 2007, 11:02:30 AM »

If all you want to do is link the to banks until you find your problem, why consume any current, put a jumper cable from bank positive to bank positive. 

Just be aware that any time you directly link two batteries/banks of different type/quality/capacity/charge state together while charging you risk doing damage to the good set by overcharging it.
 
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Len Silva
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« Reply #8 on: May 28, 2007, 11:24:33 AM »

Here is a simple circuit that will tie the batteries together regardless of which set might be dead.  It uses steering diodes to provide power to the solenoid from either/both batteries.

The circuit shown is basic. The actual connections to the diodes should come from fused sources off each battery.  The diodes should be heavy enough to carry the solenoid current, probably 10 amps @ 200 volts
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« Reply #9 on: May 28, 2007, 10:12:03 PM »

WEC -

Besides figuring out this battery puzzle, you also need to fix the audible alarms for low air and oil pressure.  Many folk disconnect them "because they're annoying", but suddenly wish they had them when the brakes fail at Oh Dark Thirty on a 6% downgrade because the compressor quit miles ago.  And we won't even mention the field day liars-for-hire would have if somebody else's crunched metal & bones were the result.

That and the fact the DOT requires them. . .

FWIW & HTH. . .

 Wink

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RJ Long
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« Reply #10 on: May 29, 2007, 04:14:12 AM »

I agree concerning the warning buzzers, I sure could have used them when my compressor went south. PO's disconnected them. I WILL hook them back up now I have a good schematic. They are there for a reason!

Paul
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Chris 85 RTS
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« Reply #11 on: May 30, 2007, 07:00:35 AM »

A couple of points about the picture shown above.  The diodes are shown backwards.  The "arrow" should point in the direction of current flow. 

http://www.eleinmec.com/article.asp?29

The term steering diode does not refer to a specific type of diode you could go to radio shack and by, but rather to a combination of diodes used in dual power supply applications.

http://www.sciencelobby.com/diodes/steering-diode.html
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« Reply #12 on: May 30, 2007, 08:07:06 AM »

Chris,

You are right on both counts, don't know where my head was on the diodes.  I was going to correct the drawing but then figured after your post it would confuse folks even more.

And yes, steering diodes are not a type but a function - I should have made that clear.

Thanks,

Len
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WEC4104
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« Reply #13 on: May 30, 2007, 10:55:40 AM »

I've been out of town for a few days, and I am just getting caught up on the posts to this thread I started. Thanks everyone for the input.  I think I'm going to stay on the caution side, and as Dallas suggested, not leave the switch in the "on" position. 

No question about it, I need to attack my root cause for the low battery situation.  Back in March I yanked my four 6V batteries completely out of the coach. I checked the water levels and individually charged each one.  I found one battery that was bad and replaced it. (Yeah I know, you should replace batteries all at once, but I was too cheap.)   At least without a load placed on them, the remaining batteries seemed to be holding a charge.  But I need to start systematically attacking this problem.

Even once I get the battery situation resolved, I would like having the ability to charge the coach batteries at the flip of a switch.  I will either do a rewire based on the circuit above (with correct diode direction), or rewire my existing switch drawing power that is not switched by the engine run circuit.

Concerning the alarms for the low air/oil pressures: I do not have any audible alarms, or at least none that work.  My dash lights (tell tales) for each of these do work.  They are very noticable, even in daylight.  With my eyes focused on the road ahead, they would still catch my attention. I assume the wiring is still in place and I could reinstall an adible alarm if I choose.  I am guessing this means I would get to enjoy the buzzer for a minute or two everytime I start the bus after it has been sitting for a day while it "airs up".   

But I am already starting to think about adding a circuit with a self-resetting "Alarm Cancel" push button. Whenever the alarm goes off, pushing a momentary push button will acknowledge the alarm and disable the audible signal. A latching relay holds the circuit in the disabled state as long as the alarm condition holds true. When the bus reaches proper air pressure, and the alarm would normally turn off, the latching signal is released, resetting the audible alarm circuit for the next time a problem condition exists.  I think I can come up with a circuit that will do this.  I'd also like to connect in an alarm for the 4104's rear door, too.     

Interestingly enough, the place that does my state safety inspection has never questioned me on my lack of audible signal. They are a huge facility and handle all kinds of commercial vehicles including semis and other large trucks. They are knowledgeable and thorough, and have been handling my inspections for 6 years.  Years ago they would not pass me because I did not have a light to illuminate my license plate in the back.  (Not that it just wasn't working, when I bought the bus it flat out did not have one)  If DOT requires it, I wonder whether old vehicles originally built without it are grandfathered, and that is what the facility assumes is my case.
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« Reply #14 on: May 30, 2007, 11:31:59 AM »

There is a very good chance that the reason your audibles don't work is because way back when someone changed the bus over to negative ground, they did not rewire the rectifiers that control the audibles.

The same buzzer is activated by LOW AIR, LOW OIL, HOT ENGINE, and EMERGENCY DOOR.
They are wired though 4 selenium rectifiers (the original solid state device) and the wiring would have to be reversed with the polarity change.
You can replace the seleniums with diodes for a cleaner set up.

Len
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WEC4104
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« Reply #15 on: May 30, 2007, 02:31:22 PM »

Thanks for the add'l info Len. It is very likely you are right about the audible buzzer being lost in the conversion to negative ground (long before my purchase).  I checked around the rear door area and there is no sign of any switch left in that area. I have a new switch to install and have already run new wiring to the dash area.

Selenium rectifiers? Is that right next to the flux capacitor?  Grin  I think I'll dump the selenium rectifiers and replace them with dilithium crystals.  That outta get my Detroit Warp Drive unit rocking.
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« Reply #16 on: May 30, 2007, 02:41:57 PM »

Selenium Rectifiers are for Real. They are the predecessor of the silicon diodes that most people nowadays are familiar with. They use a combination of selenium to make a one way device.

It they are still installed in your 4104, they are in the electrical compartment beside the drivers left arm. They are typically red in color, about 1.5 inches square and consist of several flat pieces of metal with a bolt in the center to hold them together.
Richard
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