IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Topic: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH? (Read 2739 times) previous topic - next topic

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #50 – July 17, 2017, 07:04:31 pm

Low voltage is not a problem.
Start the generator!

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #51 – July 17, 2017, 07:10:32 pm

AND turn on the boost switch.....

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #52 – July 17, 2017, 07:46:09 pm

Maybe a fly in the ointment.
Alternator Wiring Diagrams and Information - BRIANESSER.COM
Read the paragraph titled: Field Current Supply.
Now is the time for any Electrical Engineers to chime in...........

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #53 – July 17, 2017, 08:26:12 pm

That is referencing the battery cable connection. If you had the headlights on, on some cars and unhooked the battery cable with the engine running the lights would pop like flash bulbs.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #54 – July 17, 2017, 09:00:03 pm

Quote from: craneman – July 17, 2017, 08:26:12 pm

That is referencing the battery cable connection. If you had the headlights on, on some cars and unhooked the battery cable with the engine running the lights would pop like flash bulbs.

True, " After the engine is started, and the alternator is up to speed, the output of the diode trio is fed back to the regulator, and serves as a source of current for the field current. At this time, the alternator is self sustaining," The point I am trying to make is that just stopping the excite voltage from the ignition switch may not stop the alternator output after it is up to speed.
..... Like I said, time for an E.E.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #55 – July 18, 2017, 01:22:01 pm

Though I would check out the alternator situation this morning. Found that alternator excite voltage is fed from the ignition switch to a self resetting breaker under pass side dash [in my case #35] then back to alternator excite terminal. As soon a key is turned on, 12 volts is sent to this terminal. I put a jumper between breaker and wire and started engine, vmspc showed charging at 13.9 volts, about normal. removed jumper and voltage fell to 13.1 volts. The conclusion I draw is that when the alternator is turning, it self-excites to a certain extent, without the need of 12 volts to exciter terminal. Not sure of the long term effects on the alternator running like this, but if one wanted to install a overvoltage relay in this line to the alternator. Output voltage would fall enough to protect the coach electronics until you could find the problem.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #56 – July 18, 2017, 03:55:00 pm

Jim,
Good test.
I wonder what the voltage would do if you loaded up the system or even increased RPM?
Your brave. If you do something bad it would be $.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #57 – July 18, 2017, 05:12:45 pm

Quote from: John Duld – July 18, 2017, 03:55:00 pm

Jim,
Good test.
I wonder what the voltage would do if you loaded up the system or even increased RPM?
Your brave. If you do something bad it would be $.

I did rev it up to about 1800 rpm, voltage stayed about 13. Did price alternator first, about $150 on ebay.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #58 – July 19, 2017, 01:00:36 am

Quote from: jcus – July 18, 2017, 05:12:45 pm

Did price alternator first, about $150 on ebay.

Jim,

Would you please share your link? I have been looking for an alternator replacement, but never found one for that kind of money.

Thanks,

Trent

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #59 – July 19, 2017, 10:44:45 am

Quote from: TulsaTrent – July 19, 2017, 01:00:36 am

Jim,

Would you please share your link? I have been looking for an alternator replacement, but never found one for that kind of money.

Thanks,

Trent

110-555JHO / 8LHA2070VF OEM Leece Neville Alternator Reman, 12V, 160A, CW | eBay
Have seen them from $99 for new reman. Check ebay every day as the cheap ones go fast.
Just make sure frame size is the same and it is DUVAC. Anything from 110 to 200 amps will do our coaches fine.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #60 – July 19, 2017, 11:06:29 am

Quote from: jcus – July 19, 2017, 10:44:45 am

110-555JHO / 8LHA2070VF OEM Leece Neville Alternator Reman, 12V, 160A, CW | eBay
Have seen them from $99 for new reman. Check ebay every day as the cheap ones go fast.
Just make sure frame size is the same and it is DUVAC. Anything from 110 to 200 amps will do our coaches fine.

Easy conversion to make alternator not DUVAC into DUVAC alternator. Link: Prestolite - Leece Neville

Pierce

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #61 – July 19, 2017, 11:14:26 am

Reading those instructions shows removing the diode trio for Duvac. That puts us back at the possibility of cutting power from the ignition to the field.
Back to Jim is yours Duvac?

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #62 – July 19, 2017, 11:20:51 am

Yup, three different alternator configurations.

The simplest is just a B+ with either separate ground, or ground to metal of the engine.

Next adds an external sense wire-- very important with a diode-based isolator.

Next adds an ignition hot/excite wire.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #63 – July 19, 2017, 11:33:34 am

Quote from: craneman – July 19, 2017, 11:14:26 am

Reading those instructions shows removing the diode trio for Duvac. That puts us back at the possibility of cutting power from the ignition to the field.
Back to Jim is yours Duvac?

Yes, PO replaced with what coach came with. If it goes out, I would consider a standard alternator as I do use a battery combiner.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #64 – July 19, 2017, 08:25:55 pm

Our experience is finding and 'old fashioned' alternator / starter rebuilder to rebuild our alternators instead of buying reman or new, often lower quality alternator. The final outcome may be better and last longer.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #65 – July 19, 2017, 10:25:16 pm

Hi Barry,

I have a feeling the alternators for under $200 may be foreign and or reman models. Maybe I'm wrong and Ebay etc.is offering some really great prices.
Jim

2002 U320

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #66 – July 19, 2017, 11:15:56 pm

Lot of American companies remanufacture alternators, starters, turbos, etc. Taking a good quality core and rebuilding it with good quality bearings, brushes etc., does not necessarily lower its quality, sometimes it increases it. I had a bmw, and a datsun, they both had foreign alternators and starters, and had over 200,000 miles on each one with no problems.
A lot of OEM american made parts in cars had problems, and when they fail, dealer replaces them with reman parts that have improved components.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #67 – July 20, 2017, 12:31:39 am

There are a lot of lower quality starters for sale. Not sure about alternators. Just seems a shame to turn in an original unit that is probably high quality part for an unknown new or reman. Just seems like we can have our cake and... by starting with our worn and tired units and having them rebuilt by an 'old school' shop, especially if we can hang around and watch.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #68 – July 20, 2017, 12:47:51 am

Lewco in Costa Mesa, ca charged me $300 to replace a bad diode and the $70 main bearings that were a pain to get out.

Plus they have the best Bakelite old Chicago made test unit with big knobs.

Thirty year shop. I am sure he does mail stuff.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #69 – December 21, 2017, 02:43:52 pm

Quote from: wolfe10 – July 13, 2017, 12:16:57 pm

John,

Understand what you are saying, but the failure rate of a well maintained electrical system may make such a device a less than good business decision.

Said another way, the failure rate causing this is pretty low and easily identifiable. OE on Foretravels is a dash gauge showing chassis battery and the dash monitor showing house bank. Yes, one could fit even more precise gauges, but quite frankly, the OE gauges are adequate to identify this kind of issue.

Had EXACTLY this scenario on a coach I inspected recently (the first I have observed in 19 years of working on Foretravels). While on test drive, chassis battery voltage just under 12 VDC. House at 17. Immediately hit battery boost, and both instantly changed to 14.0.

An old timer, (means he was 10 years older than me!)told me in an emergency, say your chassis battery shorts out , on a diesel that turns off the fuel solinoid, engine dies, now no power steering, diesels steer quite hard with out power steering, he told me to use the combiner switch. Fast forward a few years, going down a bendy grade at 55 mph going into Sisters,OR, my engine quits, no steering, brakes didn't work, try to start engine, no such luck. I turned off stereo, wife said whats wrong, told her leave me alone for a moment please, she saw me strugling to make the turns. Combine switch pushed, dead short in chassis battery, 9 volts, yikes, engine still had not enough voltage to start, pushed gen switch to start gen, voltage goes up to 11, enough to start Cummins. Old timer saved my life. So why did my brakes not work?

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #70 – December 21, 2017, 02:53:47 pm

Quote from: Jack Lewis – December 21, 2017, 02:43:52 pm

So why did my brakes not work?

If you are talking about the air brakes on your present coach, they should have worked as long as you had sufficient air pressure. Depending on the system pressure at the instant the engine quit, you might only have one or two full applications before brake tank pressure was depleted. At that point, the emergency spring brakes should activate, and you are just along for the ride.

Re: IS THERE DEVICE THAT WILL MONITOR THE 12 VOLT SYSTEM IN A COACH?

Reply #71 – December 21, 2017, 03:57:55 pm

Thank you Chuck, your post makes me feel so much better. This happened over ten years ago driving from Eugene, Or to the 2007 FMCA, Family Motor Coach Association Rally, in Redmond, near Bend, Oregon in my 1992 Monaco Signature. I saw the air gauges dropping when I touched the foot brake, I must admit panic set in since I was almost unable to make the turns, thinking I'd soon not have brakes, and I just remembered that "old timer" telling me about the story with his combiner switch. I knew better, I knew about the springs kicking in, I just didn't at that instant. Interesting is that the Monaco combiner had an automatic spring return, and so I had to hold the combiner switch all the way into Redmond, where I replaced the chassis battery. The chassis battery was quite warm when I got to Redmond, so I am also thankful it did not catch on fire. So what happened was the chassis battery shorted out while I was driving, just as I reached the summit the voltage got so low it kicked off the fuel solenoid, as I started down the hwy to Sisters, OR., which killed the engine. Had I been in the Foretravel with a combiner switch that is either on or off, it would have been much easier. I believe it is a good thing to remember this scenario of our 12V systems. Since then, in the sales environment, with no power post near by to plug in to, I have often encountered a battery with not enough "juice" to start the main engine. Thank goodness it did have enough to start the gen set which then in turn would start charging the 12V system.

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