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Author Topic: 12v charging?  (Read 3002 times)
tekebird
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« on: June 13, 2006, 09:14:44 AM »

I have a 12v aux alternator on my MC-8. 

As of late when operating the stereo, the 12v gauge is erratic aand drops well below the charging "window".

I have not had an opportunity to check the alt output yet.

Seems to be more pronounced when the stereo is up loud.  Turn the stereo off and the gauge shows charging.

This Alternator charges the gen Battery (8D) as well as provides 12v for other things in the coach.

Any ideas?
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Busted Knuckle
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« Reply #1 on: June 13, 2006, 09:21:03 AM »

First off check the grounds on everything in the 12V system, secondly is this while driving, parked engine on, parked engine off? BK
Smiley Wink Cheesy  We have'n the "TN Fall Bus Bash" at Knuckle's, We gonna be Party'n at Knuckle's! Cheesy Roll Eyes Cool Shocked Grin[/b]
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El-Sonador
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« Reply #2 on: June 13, 2006, 01:06:39 PM »

Grounding is always an issue to check, as BK suggested, but it seems to me that a stereo uses more power when putting out higher volume, therefore adding to and may even be exciding the current draw of your alternator.

Need to verify the alternator out put under load and check its max ratings. A week or bad battery will also cause these symptoms.

You also have other variables in this equation, in addition to the stereo, as I think you said that you are also using the alternator for other things as well...


Steve
« Last Edit: June 13, 2006, 01:09:16 PM by El Soņador™ » Logged
tekebird
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« Reply #3 on: June 13, 2006, 02:37:07 PM »

May be the bettery.  It is showing just over 12v.

Alternator powers:

Front Stereo, Rear Stereo, Driver's Fan, CB, Charges Generator Batt when Gen not running, and the 12v side of my 12v/110 Refridge. when on.

Syptoms happened only when steroe and driver fan was on.....no other draw
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DavidInWilmNC
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« Reply #4 on: June 13, 2006, 02:41:07 PM »

Can you put a volt meter across the battery terminal when the engine's running?  That'll help give an idea if it's the battery or possibly the alternator.  It should be up close to 14 volts.  I'd also try putting a GOOD charger on the battery and see if it will take a charge.  Good luck!

David
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El-Sonador
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« Reply #5 on: June 13, 2006, 03:13:40 PM »

TEKEBIRD... HI

I find that thses types of issues are a simple case of "Ilimination"

First, I would check all grounds, even if you don't suspect them, it is always good to re-visit them as a Preventative Measure. [like checking your oil] Don't forget your positive terminals also. You may have to physically retighten them to be sure, as a visual inspection may not be enough to find a problem connection.

Then I would check your battery, as Dave said, you should be getting up to 14.8 volts when being properly charged. If in doubt, swap out your battery with a known good one for this test, if you don't have the proper equipment to test the batteries holding capacity.

You will still need to verify that your alternator is not only working properly, AND it  is of a sufficient size for the load you have on that system and some to spare so that the battery can get some of it for charging to replenish what you have been taking out of it.

Your battery charger must be set [if not automatic] to the proper charging rate and battery type, if it has these types of settings.  An inadvertent or accidental "nudge" of the switches on the charger when working around there could alter these settings.

You may want to also take stock of your power consumption by measuring the load each and every item on your 12vdc system is actually using at max capacity. Make sure that all items off except for the one you are testing to give you an accurate independent evaluation. Try to also measure any draw from the system when everything is off as this will indicate a possible short to ground, thus draining your system. This procedure will give you a complete inventory of the power requirements your alternator needs to produce for you to enjoy all the items you have on that system.

Do all this, ONE STEP AT A TIME, as you need to illuminate as many variables as possible, in a systematic way,  to isolate the trouble spot.

Let us know how you make out....


Steve




« Last Edit: June 13, 2006, 03:15:11 PM by El Soņador™ » Logged
WEC4104
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« Reply #6 on: June 13, 2006, 08:52:59 PM »

One additional thought to consider.  Many automotive style alternators have something called a diode packet. Multiple diodes are used in a circuit to convert the alternator's AC power to DC.  If one or a few of these diodes fail, the alternator may appear to "work", when in fact, the output is reduced.
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tekebird
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« Reply #7 on: June 14, 2006, 04:24:43 PM »

Update:

 Getting 15v off the Alt at the alternator.

Battery load tests OK
Computers says OK but was at 60% charge.
CCA rated 1155...........actual 900 something.

Hydrometers shows 3 cells at 25%
                            2 cells at 50%
                            1 cell at 75%

I had been told that a disrepancy of more than 10% between cells was an indication of a failing or bad battery.

Will recheck tomorrow after charging overnight
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El-Sonador
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« Reply #8 on: June 14, 2006, 04:32:39 PM »

Update:

 Getting 15v off the Alt at the alternator.

Battery load tests OK
Computers says OK but was at 60% charge.
CCA rated 1155...........actual 900 something.

Hydrometers shows 3 cells at 25%
 2 cells at 50%
 1 cell at 75%

I had been told that a disrepancy of more than 10% between cells was an indication of a failing or bad battery.

Will recheck tomorrow after charging overnight

I would get yourself a new battery...

Even one cell low will cause the charger to over compensate and overcharge the remaining good cells when under a charge. Plus the bad cell or cells will drag down the remaining good cells when not on a charge...

Not worth the trouble in trying to nurse it along.

Just my opinion...


Steve


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tekebird
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« Reply #9 on: July 07, 2006, 05:06:41 AM »

Problem solved.


Issue was a Selenoid.

Selenoid was controlled by 24v but allowed 12vv charging to the batt.

It was operating intermitantly.

When taken apart there was a good bit of corrosion...


30 min ID and repair by MM electric in East Berlin PA.

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DrivingMissLazy
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« Reply #10 on: July 07, 2006, 05:13:09 AM »

Don't it make you feel good to find something like this and be able to fix it!

BTW, you only have one post to go to get off the newbee status! LOL
Richard


Problem solved.


Issue was a Selenoid.

Selenoid was controlled by 24v but allowed 12vv charging to the batt.

It was operating intermitantly.

When taken apart there was a good bit of corrosion...


30 min ID and repair by MM electric in East Berlin PA.


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« Reply #11 on: July 07, 2006, 09:04:08 AM »

Where oh where did you mount a 12v alt on a MCI I have a 6V92T Charlie
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tekebird
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« Reply #12 on: July 11, 2006, 09:52:44 PM »

12 v alt mounted above blower pulley
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JackConrad
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« Reply #13 on: July 12, 2006, 04:31:33 AM »

On our MC-8 with an 8V71, we removed the OEM bus AC. We made a bracket for the 12 volt alternator and installed it where the bus AC compressor was mounted. We drive the alternator from one of the pulleys that was used for the bus AC compressor.  Hope this helps, Jack
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tekebird
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« Reply #14 on: July 12, 2006, 07:39:52 AM »

to expand a little bit.

the gm one ware alt is mounted above the blower puilley.  This requires a longer belt.

This was installed shortly after the bus was built by Custom Coach

I hyave pics posted in the MCI Yahoo group
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