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Author Topic: alternator/voltage regulator  (Read 9946 times)

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Ed Shankle

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alternator/voltage regulator
« on: August 21, 2001, 11:35:59 AM »

Lately the alternator has been squealing for a minute or 2 upon start up then it goes away. This weekend, it didn't stop and my amp meter showed it charging at 100 amps at 2000rpms and 75 amps at 1500 rpms. The alternator (75 amp Balmar)was also very hot and slightly smoking at 2000rpms.
 My guess is a stuck voltage regular. What do you think?
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Ed Shankle
Tail Wind #866 1989
Salem, MA

jmnpe

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Howling Smoking Alternator
« Reply #1 on: August 21, 2001, 03:50:09 PM »

Sounds like you have a bad case of slipping belt. The give away is the noise that you were getting when you first start up the engine.
 
 Once the belt starts to slip and doesn't stop while you are charging heavily, the slipping belt will heat the alternator drive pulley to astoundingly high temperatures, which will then cook the front bearings, and then cook the rotor of the alternator. If you are lucky, you may not have burned up the rotor, but the bearing may have been damaged.
 
 To do a simple sanity check, remove the drive belt from the alternator and give the alternator pulley a good spin with your hand. It should turn freely and quietly for several revolutions with no extra "bad" sounds. If it quickly stops, such as only about 1 turn after you release it, or if you hear "funny" noises as it turns, you have probably destroyed the front bearing and will be in need of an alternator rebuild before using it any further. Once inside, the technician may find other damage from the heat.
 
 Anytime an alternator belt howls and makes noise, it means you have either insufficient belt tension, or poor pulley-to-belt alignment, or both. In either case, you have to correct it or it will result in more problems in the near term future.
 
 The one thing you didn't specifically say was whether the batteries were known to be charged or discharged when the heavy charging started on the alternator, and what the voltage across the batteries were during the charging process. It is possible that you had a regulator "hard over", but without the charge voltage value I can't tell you if that's a probability. Did the batteries get hot to the touch as well?
 
 John
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Stu Jackson

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Howling belts
« Reply #2 on: August 21, 2001, 05:41:11 PM »

How I love that title!
 
 Only other cause of howling belts (there, I said it again!) is FOR OLDER BOATS ONLY who have NOT replaced their old ALTERNATOR BRACKETS on M25 engines.  M25 ONLY.  The M25XP "solved" the problem by giving you the upgraded alternator bracket with the engine.
 
 The giveaway in this case is the howl, which quickly stops, only because the old bracket casting has CATASTROPHICALLY failed, the alternator has slammed into the oil filter and you're filling your engine compartment and bilge up with oil.
 
 Just ANOTHER warning from one who has been there.  I even replaced an old bracket on the Universal M25 on a friend's Ericson 32 - they are good friends and I was glad to help.
 
 Just because it's still working doesn't mean it will last more than one nanosecond longer.
« Last Edit: December 03, 2009, 03:16:51 PM by Stu Jackson »
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

Ed Shankle

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alternator/regulator
« Reply #3 on: August 22, 2001, 07:31:28 AM »

John, thanks for the info.
 I didn't think to check the temp of the batteries. But the volt meter on the cockpit panel showed 16 volts.
 Also, I assume the batteries were not depleted, as the previous day the amp meter showed charging at about 15 amps, which is usual when the batteries haven't been heavily discharged.
 I'll try your alternator spin test when I'm at the boat this weekend. I don't think the belt was loose since I check it regularly. That's why I was leaning towards the regulator as the potential problem, figuring it forced the belt to slip because it stuck the alternator at a hard charge.
 Stu, my bracket curves down to the right (like a hockey stick). I assume this is the newer bracket design.
 
 Ed
 
 [This message was edited by Ed,       Tail Wind  #866 on August 22, 2001 at 07:46 AM.]
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Ed Shankle
Tail Wind #866 1989
Salem, MA

jmnpe

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To Shriek, or Not to Shriek.....
« Reply #4 on: August 22, 2001, 05:00:12 PM »

Ed,
 
 If you were seeing 16 volts on the voltmeter and you hadn't put the regulator accidently into the equalization mode (seen that before...), then you definitely had a regulator failure which basically shorts the field drive to battery voltage. I still think you have a belt tension problem because a regulator failure still can't make the alternator put out much more current than it can in normal maximum output operation into batteries that are seriously in need of charge. If the belt was howling at 75 or 100 hundred amps output during your regulator failure incident, it would howl at just slightly higher output current in normal operation. Also, your initial belt chirping upon initially starting the engine prior to the failure event signals a problem waiting to fully manifest.
 
 What size pulley do you have on the alternator? If you have the "standard" Balmar one-size-fits-all 2.5 inch x .5 inch that they put on most of their small frame units, you may get very poor belt performance with the 3/8 inch belt that you probably have on your crankshaft output drive. With the "universal" pulley, the smaller belts go all the way to the bottom of the V section, and you get an absurdly small effective pulley diameter. Even a 7/16 belt results in about a 2.1 to 2.2 inch effective diameter, and the 3/8 inch belt is even smaller...
 
 Proper belt sizing is fairly complicated, but basically is a function of drive power, pulley wrap, and pulley diameter. Belt construction also is a factor, but we'll assume using appropriate belts (i.e. - NOT covered drive belts, but belts with raw rubber edges). Assuming a typical high output small frame alternator of 75 to 110 amps, a 3/8 belt will just bearly work (OK at 75 amps and iffy at higher levels), and then only with at least a 2.7-ish inch diameter drive pulley. With a 7/16 belt, you can handle any small frame alternator as long as you have a minimum pulley diameter of about 2.5 inches. With a 1/2 inch belt, you have to go back up to about a 2.7 inch minimum diameter drive pulley because the flexing heating of the belt goes up at smaller diameters, but you can handle any small frame alternator. All of these guidelines assume that you have about 100 degrees minimum belt wrap angle on the alternator drive pulley. While you can go somewhat smaller on diameters than these guidelines, doing so will result in rapidly decreasing belt life.
 
 Stu, glad you appreciate "engineer" humor.
 
 Joh
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Ed Shankle

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alternator/regulator
« Reply #5 on: August 23, 2001, 06:05:33 AM »

John,
 Thanks for all the info. As usual, it gets more complex the more you learn.
 I don't know the diameter of the alternator pulley, I'll check this weekend.
 Sounds like you recommend that I should move up to a 1/2" belt and size the alternator pulley to accomodate that? I assume then that the diameter and width of the crankshaft and water pump pulleys on the m25xp will support that? I'll measure those this weekend as well.
 Sounds like I'll be replacing an alternator, regulator and belt.
 
 Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA

rdavison

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timely alternator discussion
« Reply #6 on: August 23, 2001, 10:00:36 PM »

This discussion on slipping belts may explain my alternator problems.  I'd be interested in any comments.
 
 We just returned from a month's trip to Desolation Sound running on a just installed Powertap PT-23 (same as the small frame Balmar), Balmar 3 stage regulator, and 460 AHs of wet cell plus an AGM starter batt.  At the beginning of the trip the alternator ran very quietly with just a hint of fan noise.  I did notice that it seemed to be running quite hot - much too hot to touch - but figured that was due to the 70 Amps it was putting out for over an hour in the hot engine compartment.
 
 By the end of the second week, I was beginning to hear some bearing noise, and by the end of the trip, the alternator was nearly as loud as the engine at higher frequencies.  Electrical performance was fine but clearly the bearings are shot.  I sent the alternator out for new bearings and bought the temp sensor for the Balmar regulator to prevent a future occurance.
 
 After reading the discussion about slipping fan belts, I remembered that the pully on the alternator showed quite a bit of inside wear.  Now I'm thinking that maybe the belt was slipping enough to create the heat and fry the front bearing.
 
 It turns out that on the Balmar regulator you can short the temp sensor inputs and cut the max output current to 35 Amps.  This probably would have solved the problem.  Of course, I read this in the fine print in the manual on the last day of the trip!
 
 My plan is to install the temp sensor and much more carefully watch belt tension and see what happens.
 
 Randy Davison  #1268 1993 k7voe
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Ed Shankle

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alternator/regulator
« Reply #7 on: August 27, 2001, 06:25:31 PM »

Ok John, I've got more info.
 The alternator dia. is 2.5" as you suspected. Hard to accurately measure the width; seems like 11/16ths at the top, but 3/8ths inside. All the pulley widths appeared to be the same. The crankcase pulley is 5 1/4" dia. and the water pump pulley is 4"
 The belt was 25/64" wide (labeled). Close enough to 7/16" to use my spare?
 The alternator seemed to pass the spin test, but just in case, it (75 amp Balmar model 91-75)is off being rebuilt and the regulator (Balmar ARSII)is being tested.
 Another major piece of info. that I'm embarrassed to admit is that I discovered the house batteries weren't holding a charge after all. My hydrometer had only 1 ball floating in each cell! (2 6 volt T-105's in series). I guess this added to the misery. The starting batteries were ok. So, I now also have 2 new batteries in the garage, waiting to be installed next weekend, with everything else.
 Any final advice on the belt width? Seems like I'd have to make a bunch of changes to move up to a 1/2".
 
 thanks for all the good info,
 Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA

Ed Shankle

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alternator/regulator
« Reply #8 on: August 30, 2001, 08:01:39 AM »

Latest news;
 The regulator was gone and needs to be replaced, as John suspected. Of course the model is obsolete and the replacement is more sophisticated and has a different wiring harness. (my interpretation; more things that can go wrong). The alternator tested ok, but I'm having it rebuilt anyway. It's out, it's at the shop, might as well do some preventative maintenance.
 Looking to install this weekend.
 
 Ed
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Ed Shankle
Tail Wind #866 1989
Salem, MA

Tim W

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Belt Tensioner
« Reply #9 on: September 05, 2001, 02:32:21 PM »

A number of years ago, I purchased what was advertised as a "drill press belt tensioner" through (I believe) Leichtung Workshops.
 
 It is essentially two threaded rods with a coupler between them. You place the rod between the engine drive shaft pulley and the alternator pulley. When the connector is turned, the rod lengthens, pushing the pulleys apart until the desired tension is achieved. The rod supports everything in place while the alternator support brackets can be tightened. Without a tool like this, its impossible to get sufficient tension on the belt.
 
 For the ten bucks or I so I paid for it, this device is well worth it. I haven't seen anything like it in a long time but I would think an auto parts store or possibly a good power tool supply shope would carry such an item.
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jmnpe

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Belt Sizes on Alternator
« Reply #10 on: September 05, 2001, 06:17:19 PM »

Well, Ed:
 
 Sounds like you have been busy. Amazing what you find once you start looking with more than a passing glance.
 
 Trying to change belt sizes on your engine will turn into a major (can you say "expensive"?) project, and I don't really recommend it. A better alternative is the power of knowledge: understanding what you need to be looking out for both in terms of regular maintenance and what to "listen" for.
 
 Your 75 amp Balmar can be driven with reasonable reliability with your existing "3/8" belt. All current belts are technically about 1/64" wider than their nominal size, so yours are really 3/8 inch, but to confuse you more, they may also be called 10mm belts, but may have a part number that would make you think that they are 11mm belts. Wouldn't think it would have to be so complicated......
 
 The main thing is to get high quality belts. If you can get one in the right size, about the best ones available are the Gates Super HC, although I just found out they are now redesigned and renamed  "Vextra". The nominal 3/8" belt is called the 3VX series. They are not handled by automotive outlets: it is an industrial belt and you will have to go to an industrial belt supplier to generally find them. With these belts, you can go down to a 2.2 inch drive pulley, but with some reduction in power capability and reduction in wear life. If you can go up to about a 2.5 inch pulley, the hp rating goes up about 30%. It's really all about how far toward low engine speed optimization you are going for.
 
 The next best will be the Gates XL automotive belts, which I believe are still sometimes called "GreenStripe" belts. These are also notched rubber-edged belts, but are not quite as robust as the industrial grade belt, but are still capable of giving a respectable performance if you monitor belt tension and pulley alignment carefully. They may be identified as either "3/8 inch" or "9.5/10mm", and the metrically sized ones will have a "11xxLLLL" part number, where "LLLL" is the nominal length in mm. Always read what the card board  product tag actually says, though. It will probably be stocked under a 4 digit number that has nothing to do with it's length.
 
 If you need help finding something other than the "universal" Balmar pulley, let me know. I have sources for a variety of diameters that will fit your small frame Balmar.
 
 The other posting about a worn drive pulley raises one or two other questions. If the pulley is just very shiny where the belt contacts it, that is normal for a fairly heavily loaded belt. If, on the other hand, there is actually an obvious "grove" or other indication of material being removed, then you have a genuine problem and you are almost certainly on your way to burning up the alternator, starting with the front bearings and going from there. The thing to remember is that there will always be heat generated at the drive pulleys. In general, the pulley should be not be significantly hotter than the alternator body, which will also be hot when it is doing it's thing. The smaller the pulley diameter, the hotter they will run at a given power. If the pulley is hot enough to burn your finger rather smartly, then you probably have too much belt slippage, or you are really pushing things near the power limit of what your belt can handle.
 
 Joh
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rdavison

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For John Nixon
« Reply #11 on: September 06, 2001, 03:44:05 PM »

Thanks for your response to my "pulley wear/heat" posting.  I've now had the bearings replaced in the alternator and reinstalled it.  Belt tension is much tighter than before.  I'll monitor the pulley temperature under high load as an indicator of slippage.
 
 Initial indications are that things are fine now.  I believe the belt was slipping but without the usual cold start squeal.
 
 Max current I'm seeing out of the alternator is 75 Amps so it should be operating in an acceptable range.  I also installed the Balmar temp sensor so presumably alternator output should limit if heat rises again.  I should see on the link10.
 
 Thanks,
 
 Randy Davison  #1268 1993 k7voe
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jmnpe

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Alternator Temperature Sensor
« Reply #12 on: September 06, 2001, 05:15:45 PM »

Randy,
 
 Glad that my contribution was useful for you. If you use quality belts and maintain proper tension, your 75 amp Balmar should have a long and happy life on your boat.
 
 Belt tension is like many things, however: even though some is good, more may not always be better. If you get too much tension, you will take out the front bearings of the water pump. I'll try to look up the general formula for correct tension based upon distance between pulleys and belt size and post it here.
 
 With regard to a temperature sensor on the alternator, these are generally intended for use on "standard" alternators used with smart external regulators, or in VERY hot engine compartments. Your Balmar, even though rated at only 75 amps output, is still built like a high output alternator and should be able to deliver near it's rated output on a continuous duty basis without need for the temperature derating that you get from the alternator temperature sensor. If the belt is slipping, by the time the alternator body heats up enough where the temperature sensor begins to reduce output current, you have probably already toasted the front bearing and/or the rotor. While the temperature sensor won't hurt anything, it may not provide the additional safety factor that you may be expecting relative to belt slippage. Best thing you can do is pay attention to tension and evidence of excessive slippage.
 
 John
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rdavison

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Belt tension and temp sensor
« Reply #13 on: September 06, 2001, 05:34:27 PM »

OK John,
 I think belt tension is about right using old rules of thumb.  Displacement with side pressure on longest span is about 3/8 inch and belt can be turned about 90 degrees with moderate effort.  Notice we're using real science here!
 
 I bought the temp sensor before your comment about slipping belts and heat.  My concern was the very high heat output from the alternator fan when charging at 75 amps.  We started to leave the small access door open which had the side effect of heating the head up quickly on cold mornings!  There's not much circulation room around that alternator with the sound proofing materal close around it.
 
 Figured it can't hurt and might help.
 
 Randy Davison  #1268 1993 k7voe
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