My GT keeps killing alternators

I'll admit I bought a lifetime warrany alternator from Autozone thinking I may have to replace it once a year.... but i'm on my 3rd one in 4 months. I'm starting to think it something wrong with the car as opposed to a spray paint rebuild from Autozone.

Do you guys know what can be doing this? It's my daily driver with no OD so at 80 she's purring along at pretty high RPM... is the constant high RPM killing these things? I've never ran into this problem with any of my classic cars. The wiring is in great shape going to the alternator too. I replaced a couple of the wires with the appropriate gauge and replaced the wires one by one to prevent putting them in the wrong place. The car is happy and drives about 1000-1300 miles then poof... the charge jewel lights up and I order another alternator.

I think after 4 or 5 replaced parts Autozone tells me to take a hike... so I better figure this out.

Thanks!

-Chris

OH... the car is a '67 GT and the alternator is out of a '75 MGB. It was converted over before I got the car.

The alternator will test bad if the battery is not fully charged. Try buying a 20-30 dollar battery charger at Walmart and see if the alternator will keep it charged up for another 1000-1300 miles. I bought a new battery and alternator and had the same problem. I think I unnecessarilly replaced the alternator I had. Also, the belt could be slipping. Also there could be a small drain on the battery that is slowly making it lose its power. Several possibilities. I ended up charging my battery overnite every week or so until I found the small drain on my battery. It was a little short in the passenger tail lite caused by too much junk in the trunk {boot?}. After I straightened out the wires leading to the tail lite, not only does the tail lite work, but I haven't had to use the battery charger.

X2 on the battery. Buy a new battery, charge it before installing it to top it off. CHECK the wires and connections are tight and clean! Can't count how many times a loose (or corroded) battery connection has bitten me in the past!

Have used AZ parts, and alternators before with zero complaints

I just went with the GM upgrade on my GT. Great upgrade!

I work for a construction company, and several times a year someone leaves something "ON" and drains the batteries. So they jump start the machine, and later on they call me saying the alternator quit. So I have to remind people, alternators maintain good batteries, but they are not designed to charge dead ones. In some rare occasions we've seen a pulley diameter too small, which spins the alternator too fast, leading to a short life of the alternator.

Thanks for the input guys, and my apologies for not giving more details to work with. The battery in the car is a duralast gold battery with 760 cold cranking amps. This battery is 3 weeks old... however i replaced the alternator that came on the car at the same time as i bought the first duralast gold battery. The first one was bulging and was a defect so they took it back.

I put new battery cables on the car and polished the grounds to a chrome like shine. I'm super anal about polishing grounds. :)

I just got back from Autozone and they hooked up their gee-whiz tester to the car. The tester said the battery was good, the diodes were good, but the regulator failed.

This alternator is showing the same symptoms of the others, leading me to believe the other two new alternators died with bad regulators too.

So my new question is... "Is there anything on my car that could consistently kill regulators?". Mind you this is a 1975 alternator and is internally regulated.

Thanks!

-Chris

Having a good battery is needed. Just take the battery up to an auto parts store and they can test it. I had a battery that kept discharging until I finally went to the auto store and sure enough it had a dead cell.

I had a similar problem on my car. It was caused by the alternator connection being loose. When the connector looses contact with the alternator, the diodes burn out. The same thing will happen if you pull off the connector when the car is running. Do not pull off the connector when the car is running or else you will surely need another alternator.

With a good battery and a good connection, your alternator problem will be fixed.

Autozone alternators have enjoyed a rather poor reputation amoung my professinal wrench folks...pretty much what you are seing FWIW.

I think I'd be talking to the store manager about a refund at this point and pay the bit more for a good alternator. I personally don't see the need for the vaunted 100 amp units but buy a name brand and I suspect the problem will end. PM me if I can help.

Somewhat on topic, I've got a weird one. My alternator light glows brighter the more I rev the engine or turn on more and more stuff. It gets dimmer and actually nearly goes out when it's idling or about to die. I'm fairly certain the alternator and battery are good but I may just test them this weekend just to be sure.

[quote=kirks-auto]

Autozone alternators have enjoyed a rather poor reputation amoung my professinal wrench folks...pretty much what you are seing FWIW.

I think I'd be talking to the store manager about a refund at this point and pay the bit more for a good alternator. I personally don't see the need for the vaunted 100 amp units but buy a name brand and I suspect the problem will end. PM me if I can help.[/quote]

That's what I have heard... but I can't imagine a company staying in business if their parts are total crap. I am doing my own non-scientific experiment. I am effectivly rebuilding my 94 chevy truck. EVERY part I am replacing on it is from autozone, including the alternator I put in a few years ago. So far FLAWLESS. No part has failed since I started this project. From new brake pads, rotors, bearings, distributor cap, rotor, wires, ign module, coil, wiper motor, alternator, battery, starter, brake drums, shoes, brake hardware..and countless other parts in my project.. not a single failure yet.

Not saying he is not getting a rash of bad alternators.. but I doubt it. Something is going on with his car.

You may be right Paul. I only know a half dozen shops who refuse to buy from Autozone anything electrical. Autozone themselves have sent reps to discuss the issues. Many, not all, are rebuilt in Mexico and not to high standards. The key here is rebuilt vs new. I have no idea if the problem continues or not. A company may get away with fooling 100 customes by offering free replacements but they don't fool a garage working on 100 customers cars. Free replacement does not translate to free reinstall.

I am going only by the posters comments about a better grade new battery and a consistant problem with the alternator and its imbedded rectifiers/regulators. I sounds like a repeated problem of bad product and why I suggest he speak with a store manager and stop the endless returns. Most AZs have test equipment in house and can isolate an issue better than we on a message board.

I am just trying to share what I know and think I know. But you indeed may be correct.

I saw a rebuilt from NAPA with bad diodes right out of the box. Many will argue there is nothing wrong with a Lukas alternator. Maybe true but I suspect poor quality replacement components...imagine getting bad replacement parts for an MGB?;) If they are sourceing the cheapest rebuild components, it would agravate the problem. Mine kept failing and I was doing the rebuilds myself with parts from the normal LBC suppliers.

I agree with Robert on this one. I'd talk to the manager. If you can't get a refund (doubtful) maybe they would let you trade towards a Bosch or GM conversion.

You don't have any extra accessary loads do you? Electric fans, big stereo??

[quote=kirks-auto]

You may be right Paul. I only know a half dozen shops who refuse to buy from Autozone anything electrical. Autozone themselves have sent reps to discuss the issues. Many, not all, are rebuilt in Mexico and not to high standards. The key here is rebuilt vs new. I have no idea if the problem continues or not. A company may get away with fooling 100 customes by offering free replacements but they don't fool a garage working on 100 customers cars. Free replacement does not translate to free reinstall.

I am going only by the posters comments about a better grade new battery and a consistant problem with the alternator and its imbedded rectifiers/regulators. I sounds like a repeated problem of bad product and why I suggest he speak with a store manager and stop the endless returns. Most AZs have test equipment in house and can isolate an issue better than we on a message board.

I am just trying to share what I know and think I know. But you indeed may be correct.[/quote]

Generally (with the Bs at least) I am in the camp of buying the best of the best of the best parts if possible.

A crappy part with a lifetime warranty is still a crappy part.

Not defending AZ, but I do have to say, at the mechanics class I am in, I can tell you that I get fewer (actually zero) ill fitting parts (or failing) from AZ than the other students who buy from napa, car quest, etc. But I am a sample of one, so it means Jack about their products as a whole. But the rebult alternator in my chevy truck is humming along quite nicely years later. I do hear at class, especially from the instructors, that AZ parts are crap and don't fit or don't last. I just have not seen that in my limited experience on one car model. Maybe I am super lucky, but I think their products are better than their reputation indicated (kinda like MGBs!!). Yes many of their parts are made in Mexico, china, etc. I won't put them on my B, but for my truck, heck I will try it! No way will my truck last as long as my B, thats for sure!

For a B in the opening post, I would either go with a new Lucas (they seem to last decades if the car is maintained), or the GM/Saturn. I have one of each in either of my Bs, both working well.

[quote=78mgb]The same thing will happen if you pull off the connector when the car is running. Do not pull off the connector when the car is running or else you will surely need another alternator.

With a good battery and a good connection, your alternator problem will be fixed.[/quote]

OK... I think we're onto something here. The power wire coming off the really wide middle terminal has slipped off the car once before... and this time around the connector broke and I drove the car for a few miles back home with the power wire off.

Could that fry the regulator?

This next alternator i'm going to drill and tap the power terminal on the alternator so I can securely screw the wires to it with an eyelet. The slip fittings seem to slip off, or they break... even when soldered..

Having the power lead from the alternator disconnected from the battery while the engine is running is not good. When that lead is disconnected the alternator output can reach upwards of eighty volts causing catastrophic failure of the alternator diodes.

NOW you tell us. No doubt the issue is the the slipping wire and not AZs product...maybe....

80 volts!

Crap!

Well... sounds like we found what happened then...

The new alternator comes in tomorrow morning. I'm going to figure out some way to keep that wire on!

Thanks for the input.

-Chris

If the alternator light is coming on, that is almost certainly due to a blown diode in the rectifier pack. You can replace it without changing the entire alternator. You do need to solder, but it is quite easy and straightforward to change. Both Moss and VB stock the diode packs.

When that lead is disconnected the alternator output can reach upwards of eighty volts causing catastrophic failure of the alternator diodes.

This is correct - when you unplug the alternator the magnetic field collapses (abruptly) and the voltage can surge dramatically. Automotive diodes are probably only rated at about 30v so the chances of puncturing one of them is high.

The most likely cause of recurring blown diode packs is a loose connector. Unplugging an alternator under load is a Very Bad Thing. It won't always blow the alternator, but there is a reasonable chance it will - say 1 in 5. If you have a loose connector then it may jiggle and effectively unplugs itself. If it does this enough times, sooner or later you'll blow a diode.

Other causes of blown diodes are giving people boosts with the engine on. Yes - I know everyone does this - but it is really hard on the diodes. Fortunately, our Lucas alternators have such low output that they usually don't blow diodes as often as Delco or other alternators under these conditions. Also, letting the alternator charge a completely dead battery can be hard on diodes.

Heat is a killer for diodes or any other electronic component. Before I found out how stupid a college educated electrical engineer such as myself can be, I had a bushing on the alt. start to make noise. I disassembled the alternator, cleaned and greased everything, etc. Put it all back together and it lasted about a week and the alt light came on. Fried diode. I ordered a new diode pack from Moss, and a week after I put it in, it fried again. Grrr...junky parts. I ordered another and when the alt light came on again, I parked the car and disassembled the alt again. Only then did I realize that I had put the pulley on with the fan blades facing AWAY from the alt. No air, no cooling. Humbling experience. Replaced the faulty diode with a good one from the previous attempts at repair and never have had a problem since. Always check the obvious before you blame the parts store.

Never make the same mistake twice...there are plenty of new ones!