surging GM alternators

[dacflyer]

i have noticed here at work on many of the GM vehicals we have..mostly on the trucks..
that the alternator seems to be surging..
the lights etc pulse brighter than normal
at a steady rate..its acting like the regulator is kicking on/off like the old fashion relay types of long ago...but the regulators on these newer models 95 and up are acting wacky..
and i know that these regulators are built into the alternator self contained..
anyone got any ideas whats causing this to happen and why its happening to so many vehicals?
the surging is at about a 1/2sec or less..you can notice this more when the headlights are on or when someother heavy load is on..talked to a few other people and they said they had to have their alternator replaced...but to have it happen again after a yr or so..

[terri]

The smartest thing you can do is check out the TSBs (Technical Service Bulletins) for your vehicles ANY time something is goofy.<p>I'm sure you can Google these out without me doing the legwork for you.<p>Back in 1976 I had a brand new new vehicle which kept stalling and the dealer said the "ignition module" (the older version of the on-board computer) had to be replaced for something like $US 150 --this was in 1976 dollars, mind you.<p>So I checked with the salvage yards for a used one and finally talked to an old "yardmaster" who said, "Oh, there's a TSB on that. The dealer will replace it for nothing."<p>I discovered that many times dealers will charge you for a "fix" where they don't tell you the manufacturer will fix it based on the TSB for that problem. So I got a copy of the ignition module TSB from the manufacturer and walked into the dealer with it. They grumbled and mumbled, but they replaced the unit for free.<p>My New York "street paranoia*" tells me that sometimes they might be tempted to double-bill for a lot of these things --they bill you and then they bill the factory.<p>Nowadays, with the Internet, you can check out these TSBs for yourself with ease, and not get screwed.<p>Over the years I have saved quite a couple of
$US Bucks by checking these TSBs (Technical Service Bulletins) for myself, and armed with this info, had stuff fixed for free. Not all the time, but pretty darned often.<p>On a general note, any time there is oscillation, check for faulty feedback. Quite possibly just a faulty connexion from the sense wire to the alternator. Burring these connections with a pair of dykes might cure this. Or, it could be internal to the alternator.<p>*"Any way they can part you from your money,they will."<p>[ January 31, 2005: Message edited by: terri ]</p>

[chapter30]

This is a common problem in some GM cars. Also watch out for all of the lights to appear extremely bright. This is a sign that the voltage regulator has gone completely.<p>I have found that the best way to deal with this issue is to replace the alternator with either a brand new one(most expensive) or a rebuilt one from an electrical shop. The important thing to remember is that you get the rebuilt part from a shop that knows their stuff and completely rebuilds the alternator. Many places will only replace the bad parts, say the brushes, only to have the regulator fail shortly after they sell it.<p>I am not sure what causes this problem.

[jwax]

I just read in an auto electronics text that some newer vehicles "full field" the alternator, disconnect all other electronics, and apply the 70-90 VDC to the windshield heater! I wasn't aware of that dangerously high voltage being in auto wiring, except for plug wires! Be careful!

[terri]

Yeah, in fact a couple of decades ago somebody published a method of buggering up the regulator connections so you could draw out about 110V DC and run it to a regular houseld outlet to run 110V devices with universal motors (That is, those with brushes, like electric chain saws, circular saws, vacuum cleaners, etc.) Also for resistance-type appliances like electric coffeepots, etc. You had to watch for max wattage, of course.<p>This was intended for construction-type people and folks like me who had an electric chain saw.<p>Sounded scarier than heck to me, so I never tried it. I just stuck with my gas-powered generator for these things. That's how I got to be 65 with all twenty fingers and toes --by paying attention to when I was scared.<p>I still think the best thing to do is, and I repeat myself and reiterate and say again, once more, over and over, repetitively and redundantly, and yet again one more time:<p>CHECK THE TECHNICAL SERVICE BULLETINS (TSBs)!<p>BEFORE mucking around with it and voiding the possibility that the dealer might do it for free.<p>[ January 31, 2005: Message edited by: terri ]</p>

[Chris Smith]

Check your voltages and see if they are rising, or just lowering because of a load? It might not be the alternator. It might be a load kicking in?

[dacflyer]

they are not loading down...its definatly peaking to almost 18 volts..or more... the voltages are
YoYoing... rember the old mechanical regulators of yesteryear? they had a relay that pullen in/out as the battery needed charging..relay kinda buzzed.. but when contacts wore.you could tell it by the lights and ampmeter fluxuating...

[terri]

Go ahead. <p>Ignore me. <p>(Snif.)<p>http://www.alldata.com/recalls/index.html<p>Incidentally, the best way to break up oscillations (like in your charging ckt) is to change the time constant involved in the feedback loop. <p>Like by introducing a reactance into the circuit.<p>Like a capacitor.<p>Like across the sense lead going to the alternator and gnd.<p>Like one from an old cheapo camera flash unit.<p>Or like that there.<p>(Snif.)<p>You might want to check to see if there is an absolutely, positively 100% solid ground connection between the engine/alternator frame and the chassis. And I don't mean with a ohm-meter. I mean by measuring the voltage between the alternator frame and the chassis of the vehicle while it's running and the headlights are on and this connection is actually carrying some real current. There should be almost no voltage appearing if the ground connection is indeed 100% "solid." (Don't get the leads caught in the belting. I speak from 'sperience.)<p>But who am I to make such suggestions?<p>(Snif.)<p>So go ahead.<p>Ignore me.<p>See if I care.<p>(Snif.)<p>[ January 31, 2005: Message edited by: terri ]</p>

[Crowbar]

//You might want to check to see if there is an absolutely, positively 100% solid ground connection between the engine/alternator frame and the chassis. And I don't mean with a ohm-meter. I mean by measuring the voltage between the alternator frame and the chassis of the vehicle while it's running and the headlights are on and this connection is actually carrying some real current. There should be almost no voltage appearing if the ground connection is indeed 100% "solid." // That's where I would start, check all your connections first, if your going to 18 volts still, you have a bad regulator. Might be worthwhile also to check the ripple, a bad diode trio while often burning open can also short imposing AC on the DC bus.

[jollyrgr]

Most automotive alternators have what is called a DIODE TRIO inside them. This is exactly what the name implies; three diodes in the same case. There are three coils inside the alternator. The coils are rectified by one of each of the three diodes in the package. Each coil gets its own connection to the diode and the three diodes come to a common connection. <p>If a diode should open or short you would get what you describe; the pulsing effect. At least this has been the case when GM alternators have had a diode open/short on me. And yes I have had them go both ways. When a diode shorts you up with a dead battery after a few hours. Also with a shorted diode you get a super hot alternator. If you drip a small drop of water on the laminated plates you might even see steam come off. (Don't worry about mixing water and electricity; I'm not talking about gallons of water just a couple drops.) An alternator does get warm as it operates. But one with a shorted diode will get hot enough to brand you if you touch it.<p>When a diode opens on you it is a more subtle experience. With lots of short drives the battery appears weaker and weaker. After a long drive the battery gets charged and you don't notice a problem again until the battery is slowly discharged again. As Crowbar says, put a volt meter on the system and check both DC and AC voltage. You should see little or no AC ripple. <p>As to Jeff's comment: He is exactly right as to how some shops do this. I was told long ago (and don't recall the exact terms they used) there were many ways to buy automotive parts. Working versions out of a salvage yard. A rebuilt item (where they fix the failed part inside the item), an overhaul (where they replace all the likely parts to fail like brushes, diode trio, and regulator), and brand new. I may have transposed REBUILT and OVERHAUL as I cannot recall which was which. <p>In any case I found that I could buy a rebuild kit for about $10 that contained the diode trio, brushes, and fresh high temp grease for the bearings. For a quick job I buy a "LIFETIME" warranty alternator. For my GM cars they were under $100. Trak Auto used to be my favorite place to go as they were all over the country and never argued with me when I brought in a failed item. They are, alas, no longer in business. I now go to a local small chain that has the same warranty. I have to do a bit more arm twisting there for warranty exchanges as they don't hire car people to sell the automotive parts. Usually I end up getting waited on by a high school girl that has no clue what I'm exchanging unless I tell her. Most places charge a core charge for the old alternator. In my case it was a staggering $5.00. So what I do is buy the new alternator and pay the five bucks knowing I will not be returing my "dead" unit. I Put the new alternator on and then rebuild the broken one myself when I have time. Thus the next time I have a failure there is a spare on my shelf. I put this in the car until I get time to go to the store and swap the warranty one. Since my mom, dad, brothers, and I drive cars that all have the same alternator in them this one rebuild has been in several cars.<p>[ January 31, 2005: Message edited by: Jolly Roger ]</p>

[josmith]

Lots of speculation. If you suspect charging problems there's nothing like a dmm to check it out. I've seen some cars that have their lights on in daytime running mode where they flicker for more visibility.Can't say that gm cars were included or that i've seen any rash of surging lights on gm cars.

[Chris Smith]

If you have 18 volts, no need to go any further. <p>Replace the Alternator or completely rebuild it, and check the windings to see there is no leak to ground. <p>A common mistake made by many re-builders is to overlook this. <p>Replace the brushes, the Regulator, and the diode trio, and then check the coil leads to them self for opens, and coil leads to body of the alternator for leaks. <p>Use a mega ohm setting for the leak to ground, and NO leaks are tolerable because as they warm up, the resistance decreases and can short out, over load, or just cause havoc. <p>I have repaired a few thousand Delco’s, Chryslers, Fords, Bosch, Marellis, French, and Nipon Denso’s alternators in my time. <p>Also Replace or check the cap, if one is installed.

[Clyde Crashkop]

You might test the battery to make sure it's good. Maintenance free bateries get low on acid/water too but they want you to buy a new battery. If you peel the label off the top of most batteries you will find removable caps that you can take off and add water.

[dacflyer]

terri no crying allowed inthis forum ....lol\
wasn't ignoring you...
i was mostly speaking from past experience..the vehicle had the problem fixed long ago,,but i was wondering mostly if anyone else had this problem and what did they find out..is it regulator failure? or something else?
seems like its a common problem and often too..
them alternators are getting smaller and smaller and yet more demand is put on them as well
i rember my old ford alternator (90 amp) was huge
now you can find them really small almost 1/2 sized..

[terri]

Oh, OK. (snif)<p>It's all better now. Sorry.<p>Need new box of tissues.<p>snif<p>I agree on the shrinkage of these devices. Seems even with higher efficiency designs, there's a lot of heat to be dissipated in ever-smaller packages.<p>Amusing thought: they'll get so small, they'll have to add lotsa fins to get rid of the heat. Thereby making them bigger again.<p>DIGRESSION: At one point in electronics history, they were using "peanut tubes" (valves) in things like hearing aids and artillery proximity fuses. They were pretty tiny --some as small as a quarter inch in diameter and maybe 5/8 of an inch long. <p>Son-of-a-gun if they didn't add heat-dissipating fins to them in one application I saw recently. (This was in one of those Civil Defense radiation monitors you can get off e-bay. They used a CK-5886 as an electrometer tube (valve).)<p>So there's this eensy-tiny tube (valve) with a metal clip around it with fins on it, which doubled the size of the assembly!<p>Incidentally, these tubes (valves) were whimsically called "glass transistors" for a while. :END DIGRESSION<p>But don't worry. I'm all bettah now.<p>snif<p>[ February 01, 2005: Message edited by: terri ]</p>