Home » Public Forums » GMCnet » [GMCnet] Alternator short life
| [GMCnet] Alternator short life [message #346726] |
Thu, 22 August 2019 10:53  |
glwgmc
Messages: 1014
Registered: June 2004
Karma: 10
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There have been many posts about short alternator life. Most who experience this phenomenon blame it on cheap or improper rebuilds, especially among those sold by chain auto parts stores. While that may well play a role, the research I have been doing for a talk in early Oct at GMCWS suggests another cause as well.
Our alternators were designed only to recharge lead acid engine starting batteries, a task that normally takes only a short period of time. In coach use the alternator is also pressed into service to recharge our house batteries as well, a process that takes considerably longer. That means the alternator is outputting more current for a longer period of time than it was designed to do. This can quickly overheat the diodes and cause premature failure.
Larger alternators designed for industrial marine, bus and truck applications employ things like oil cooling of the diodes so they can withstand the heat built up from higher duty cycle applications than our GMC alternators could ever tolerate no matter who rebuilt them.
I am now convinced that an alternator duty cycle manager is a must have addition to keep our alternators alive in the high draw application of a coach with an inverter. I will detail the what and how in that presentation that will be released for publication after given.
Jerry
Jerry Work
Kerby, OR
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Jerry & Sharon Work
78 Royale
Kerby, OR
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| Re: [GMCnet] Alternator short life [message #346768 is a reply to message #346726] |
Fri, 23 August 2019 12:15  |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
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With that in mind the original 4D house battery may be a better choice than 2 x 6V golf car batteries in series. A case, once again, where more and bigger is not better. My 4D is about 10 years old and working fine. Our alternators were the HD large frame cop car 80A type, so with a group 78 engine and 4D house they should survive as that was how GM tested the setup.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Alternator short life [message #346775 is a reply to message #346726] |
Fri, 23 August 2019 13:54 |
timthenomad
Messages: 63
Registered: June 2015
Location: Austin, TX
Karma: 5
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Quote:In coach use the alternator is also pressed into service to recharge our house batteries as well..
or our house batteries, 2 laptops, 3 cell phones, an iPad ....
Tim Taylor
Austin TX
Philadelphia PA
76 Birchaven (SB)
76 Triumph TR6
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| Re: [GMCnet] Alternator short life [message #346788 is a reply to message #346726] |
Sat, 24 August 2019 00:10 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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There is some truth in what jerry suggests I used to have some trouble with the alternator when I relied on the alternator to replenish my golf cart batteries . When I replaced the original converter with a plus 40 and used the generator to recharge the cart batteries while dry camping my alternator problems ceased.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Alternator short life [message #346789 is a reply to message #346788] |
Sat, 24 August 2019 07:36 |
6cuda6
Messages: 975
Registered: June 2019
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It also doesnt help that we have a constant load on both batteries while driving.....in general the single car battery arrangement is a pretty easy environment....start engine, recharge battery, suppliment battery load if needed.
RV set up has to do the same plus charge house battery which is feeding a load continuously (fridge, inverter, fans etc).
In the car stereo world, if you needed more power for amplifiers you added batteries and if you added batteries, you added another alternator for those batteries or you simply ended up shutting down the car because you consumed more power than you could feed or you killed the alternator pretty fast no matter how big it was.
Perhaps the solution to multy battery setups would be adding a second dedicated alternator? Anyone do this yet?
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] Alternator short life [message #346792 is a reply to message #346789] |
Sat, 24 August 2019 10:33 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Having a second alternator sounds good.
Having and run 35 years and million miles on the GMC MHs and repaired them
on the road, having extra accessories on the coach to deal with when things
like the water pump goes out is my concern.
If you are the type to have a shop do most, that is fine, but when a
mechanic sees the extra items mounted, they turn cold and refuse to want to
work on it.
We see enough of that type here in our shop and see how that makes our
techs hate working on them and presents a problem when it comes to trouble
shoot problems.
I do thing like ; run LED bulbs and other electrical conservation to not
over burden the electrical.
Even leaving the radio on when stepping out or leaving porch light on all
night and day can burden the battery.
On Sat, Aug 24, 2019 at 5:37 AM tonka6cuda6--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> It also doesnt help that we have a constant load on both batteries while
> driving.....in general the single car battery arrangement is a pretty easy
> environment....start engine, recharge battery, suppliment battery load if
> needed.
>
> RV set up has to do the same plus charge house battery which is feeding a
> load continuously (fridge, inverter, fans etc).
>
>
> In the car stereo world, if you needed more power for amplifiers you added
> batteries and if you added batteries, you added another alternator for
> those batteries or you simply ended up shutting down the car because you
> consumed more power than you could feed or you killed the alternator pretty
> fast no matter how big it was.
>
> Perhaps the solution to multy battery setups would be adding a second
> dedicated alternator? Anyone do this yet?
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Alternator short life [message #346793 is a reply to message #346789] |
Sat, 24 August 2019 11:31 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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I have had only one alternator failure in 11 years and 44,000 miles, and that was about 4 years ago. I* suspect my solar charging system has something to do with it as it is constantly keeping my house batteries (and the chassis battery, through the combiner) charged. I'm sure that lessens the load on the alternator somewhat.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: [GMCnet] Alternator short life [message #346794 is a reply to message #346793] |
Sat, 24 August 2019 12:01 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
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I am wondering what is the real issue here.
We have had one alternator (an 80amp 27SI) for 15 seasons and about 70K miles and the coach is a 23 (House bank in the front) and when I installed the Bogart monitor, I saw it was kicking out 98amp after a long dry camp. I was surprised to see this, but have confirmed the value with a Hall/Fluke set. We did have trouble with belts (100amp being the limit of a single belt) and know I knew why. We do have electric refrigeration and a house bank that is a pair of GC2s (T-105 actually now) with the short heavy cable. I am actually surprised that the diode isolator has put up with this.
Yes, that alternator just died because it sucked in a pebble in SC and the extra load made the double sheave spin on the shaft. I am trying to find a good replacement, but the high output 27SIs are getting kind of short. I would like to repair this one, but if I can't I will try to find another. I do have to find another soon because the engine is just a few days from going back in.
There is also available a 27SI-200 that was used on some special service in the early 80s. I acquired one. This was a mistake. It may be a 27SI as to model, but the thing is a monster and will not go on the same mounts. If you want it, I will make you a deal.
Matt - back out to the shop and planning on Mansfield
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Alternator short life [message #346796 is a reply to message #346775] |
Sat, 24 August 2019 13:53 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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I think that you are making more of this than is necessary. You are dealing with a 40 year old mechanical device that has been operating in some time very harsh conditions. It is in an enclosed area that get upwards if 200 degrees and occasionally has water splashed on it. It is expected to also work equally well at zero degrees and all temps in between.
They quit on occasion due too the extreme conditions, age, and wear. Replacing them with a good rebuilt or rebuilding them yourself with quality components is the key response. The load on the alternator is not that high. Re-charging batteries, while high current initially, the rate rapidly drops off as the batteries start taking a charge. After 5 minutes the rate is below 30 amps and the rate reduces from there to basically nothing as the batteries take a full charge. The batteries just will not take anything higher for any length of time. The only other high current device that you might have not see in a car is a an electric refrigerator and it is an intermittent load. I replaced my alternator with a 100 amp one with a slightly smaller pulley. Why? It was a a free easy upgrade after my engine fire and I get more charging current when the engine is at idle or very slow speeds. The 80 always did the job trouble free.
I suggest that you install an amp meter (temporary or permanent) and see what you are really using before if you start dreaming up upgrades. The police and other emergency vehicles put on a larger alternator to get higher capacity, what but they are really upgrading is their capacity too supply emergency lighting, etc. while parked and running the engine at an idle.
Find out what the real loads are (long and short term) before wasting money and time on an upgrade / change.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alternator short life [message #346798 is a reply to message #346726] |
Sat, 24 August 2019 16:12 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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"I suggest that you install an amp meter (temporary or permanent) and see what you are really using before if you start dreaming up upgrades."
Uh <koff> it's been brought up before. Ad nauseum, and it's right, you should have at least a chassis and correctly each system should have an ammeter.
I'm still debating. I may move the (it will be only one) house battery up front. I hafta run a new rear (Onan) heavy cable, the current one is of many colors, none original.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Alternator short life [message #346839 is a reply to message #346796] |
Sun, 25 August 2019 17:04 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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I'm going to agree with Ken on this one. The GMC alternator works hard, but is our engine compartment really much hotter than a Toronado on a sunny day? (Huge steel hood soaking up sun within an inch of the alternator, A/C cranking, maybe towing a trailer, etc?)
I'd like to suggest a possible alternate cause for some of these failures. Our alternators are remote-sensing. A separate wire goes (indirectly) to the chassis battery, and the regulator uses that voltage to decide how much output is needed. A failure of the sense lead will send the alternator into full output. Like any automotive alternator, the Delcotron is capable of over 100 volts at full field/no current. Years ago "they" sold a clever device for externally-regulated alternators which allowed you to plug in your electric power tools so long as they had a "universal" (brush-type) motor. The device disconnected the alternator from the battery and regulator, full-fielded it, sent its output to a voltmeter and 120V socket, and provided a hand throttle for the engine. You plugged in the tool, eg; electric chain saw, and revved the engine until it read 120 volts (DC). The stock output diodes withstood this voltage in most cases. An internal regulator might not.
Returning to our GMCs, we have an absurd 10ga wire carrying the full alternator output to a marginal 60 amp diode isolator. Can you say major voltage drop? If the sense wire isn't seeing 14 to 14.5 volts at the coach battery, it's going to call for "MORE" power, which the alternator tries to supply. Might this produce voltage enough to damage a regulator or diode trio?
FWIW, one of the first mods I did to my Eleganza 20 odd years ago was to install an 8ga wire in parallel with the 10ga to the isolator center post. I also replaced the 60A isolator with a 120A unit from J.C.Whitney. (It just fits mounted horizontally on the firewall.) I've had only one alternator failure in 20 years, and that due to the internal buss bar from the diodes to the B+ terminal working loose, with an effect similar to that described above.
HTH, My .02, YMMV
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: [GMCnet] Alternator short life [message #346840 is a reply to message #346726] |
Sun, 25 August 2019 17:26 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Doesn't that stock 10ga wire act as a current limiting device by design? Adding a lower impedance load to the output puts more strain on the internal diodes as they have to pass more current. However I bet there is only a 1/2V drop between alternator post and isolator post. A meter between the 2 at max load ( lights, hi blower, refer on DC, discharged house battery) and 2000 RPM or better would tell.
To dispel the myth for the Turbo Regal guys where they say the 120 CS144 needs to be a 200, this test was done. With every electric thing on full blast including rear def and both windows and horn, load was under 90 A and that car uses 10Ga wire as well.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Alternator short life [message #346905 is a reply to message #346840] |
Mon, 26 August 2019 17:09 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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I do not think so. Why would you want to install an 80 or 100 amp device and then limit it's current. I think it was an expense limiting device. 10 ga. is cheaper than 8 ga. or 6 ga. Why did GM eliminate tooth washers on the Colorado when they used them for electrical connections on it's predecessor the S-10. I think it saved them $.10 per car in parts and 30 seconds in assembly time.
I did what you did and added an 8ga. wire in parallel to the existing 10ga. bur out of the isolator we are back to 10 ga again. So I am not sure if I gained much.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Alternator short life [message #346908 is a reply to message #346726] |
Mon, 26 August 2019 18:37 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Ken since it's the Amps that takes out the Alternator OP diodes, not voltage, and the sense compensates for the Voltage drop , the Voltage at the alternator terminal will be higher, but current limited by the wire size. The same principle Yandina uses to prevent overcurrent on their relay contacts. Undersized wire of a specific length.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Alternator short life [message #346912 is a reply to message #346908] |
Mon, 26 August 2019 22:14 |
Rick Staples
Messages: 126
Registered: May 2014
Location: Johnstown, Colorado, USA
Karma: -1
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FWIW,
From my ancient "Delcotron Generator and the Charging System" training manual published by Delco-Remy way back in 7/1/69: "No current control of the Delcotron is necessary since it is capable of delivering only a given amount of current."
From the Chevrolet P30 chassis manual included on the GMCMI thumb drive:
"NOTE : If GM factory systems are changed, the size of
the main charging wire in the harness must be
changed from a 3mm or 12 AWG wire size to an
8mm or 8 AWG wire size. The larger size charging
wire is mandatory when installing an upgraded
charging system."
From the dim recesses of my memory of high school auto shop circa 1965: "Alternators are self-limiting for current."
I'm really not trying to put anyone down on this one. As I used to tell my customers "I had to walk AROUND the pond on my way to work. I don't walk on water." I've learned a lot from the good folks on this site. So I could be wrong, but I don't think so this time.
And yes, adding the 8ga wire DOES help, as more power is now available to recharge the house batteries, run the A/C high speed blower, run the refrigerator, and supply all the other loads that DON'T get their power from the chassis battery side of the diode isolator.
HTH
Rick Staples
Rick Staples, '75 Eleganza, Johnstown, CO
"Advice is a dangerous gift, even from the Wise to the Wise, and all paths may run ill." -Tolkien
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| Re: [GMCnet] Alternator short life [message #346923 is a reply to message #346726] |
Tue, 27 August 2019 08:52 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Very interesting. Love factory facts. . I wonder how it applies.to our external voltage sense and isolator situation. Seems any drop at or before the junction point would be made up automatically.
Other than bearing and brush wear which are both easily and inexpensively replaced, I have not had any Delcotron failures on my vehicles.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Alternator short life [message #346924 is a reply to message #346923] |
Tue, 27 August 2019 09:15 |
Justin Brady
Messages: 769
Registered: April 2015
Location: Bell Buckle, TN
Karma: 11
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I'm with Ken on this one, Even with a larger load than optimal It's never going to run near full output for very long because the battery bank is not big enough to draw that much current for much time.
I run 4 6v golf cart batteries and when they are low after a few days camping I see 60-70 amps output for 2-3 minutes before it starts to taper back.
I'm more inclined to blame low quality rebuilds for this one. I'm on my 3rd alternator on my boat this summer because the quality is so low.
Justin Brady
http://www.thegmcrv.com/
1976 Palm Beach 455
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| Re: [GMCnet] Alternator short life [message #346968 is a reply to message #346726] |
Wed, 28 August 2019 11:47 |
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ljdavick
Messages: 3548
Registered: March 2007
Location: Fremont, CA
Karma: -3
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I read an interesting article on Jalopnik. It's new to me, but published January 13, 2017, about 48 volt mild hybrid systems. The article went into some detail about the various ways auto makers are using "low voltage" systems to increase efficiency. The big motor / generator replaces the alternator and provides power to the 48 volt system, that includes a 12 volt converter for chassis power, and is supplied power from the 48 volt battery to spin the crankshaft -- transmission -- wheels when needed.
https://jalopnik.com/everything-you-need-to-know-about-the-upcoming-48-volt-1790364465
<https://jalopnik.com/everything-you-need-to-know-about-the-upcoming-48-volt-1790364465>
I'll bet it's not long before hobbyists make retrofit kits just like my fantastic Howell EFI replaced my carb, disks can replace drums, and satellite and streaming music is replacing old radios.
I particularly like the idea of spinning the accessories decoupled from the engine. Air conditioning compressor, power steering, vacuum booster, and water pump can be powered as demand dictates and not just as RPM's allow.
Cool Beans and these coaches may never die!
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy
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