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I've been having issues with my 84 corvettes alternator. I've gone through 5 within a year. They last about a month and just stop sending power period. They read 14 volts when I get them and after a few weeks I notice a drop in voltage. I don't know if something might be pulling to much power and shortening the life of the alternator or what. It's the same with every on I put on there. The battery I have in the car is less then a year old and the connections to it are clean. Not sure what's causing it.
I've been having issues with my 84 corvettes alternator. I've gone through 5 within a year. They last about a month and just stop sending power period. They read 14 volts when I get them and after a few weeks I notice a drop in voltage. I don't know if something might be pulling to much power and shortening the life of the alternator or what. It's the same with every on I put on there. The battery I have in the car is less then a year old and the connections to it are clean. Not sure what's causing it.
Just because the battery is less than 1 year doesn't mean that it's OK or even borderline. There are many reasons you could have multiple or similar recurring failures and nearly all can be diagnosed with proper load testing of the entire electrical.
Your location is? The alternator source is?
Clean can't be used as an indicator of a quality connection to the battery. If you had proper devices you could do the diagnostics yourself but with the recurring I'd have thought if you "could've you would've" so I'd suggest a "for hire" diagnostics of the electrical system.
In the right margin there are likely other "good reads" on the NAPA site. There are many other more technical reads but these are just very straight forward and quite easily understood.
These are just good reads but for yours I think a for hire with a proper "carbon-pile" high quality load tester is called for.
Poor connections are the biggest killer of electrical parts. I would make sure your ground terminals are including battery cable to block are clean and tight,Alternator connectors are in good shape, and if you added accessories where they connect to battery voltage. On an 84 voltmeter can read 13.1-5 is normal. As long as alternator can keep up with electrical demands at 1500 rpm it's probably ok. It is not uncommon in high load situations(lights,wipers, defroster) for alternator to be overwhelmed at idle. If you have added high draw accessories you may need higher rated alternator.
What in the alternator dies? If it is the regulator I've seen a situation where a pin hole in the upper radiator hose (caused by contact with the alternator electrical plug) sprayed coolant directly on the regulator and killed it. Everything evaporated so there was no clear trace except corroded regulators. It only sprayed when the engine was really heated up.
The more likely cause is junk rebuilds. The best fix is a reputable local electrical shop doing a heavy duty build. Don't use "Power Pulleys" they cause under charging at low RPMs with the 84 alternators.
1984z51auto hit the nail on the head. What is the failure mode - regulator or something mechanical in the alternator. Have all the rebuilt alternators been from the same place ???
Assuming it's the regulator that's failing, you can do some simple stuff yourself. In addition to checking that the grounds are all good - I'd suggest doing a little diagnosis. Try to borrow an inductive (clamp over or clamp around) current measurement meter that will work on a DC supply (they exist but are significantly more expensive and therefore less common that units that read AC current only). Put that around the alternator main output line, start the car and see how it behaves - with no other accessories on - the car should not need more than about 5 - 10 amps to run - so anything above that is battery recharging. The current required to recharge the battery should diminish fairly quickly.... If you're seeing 20 or so amps after about 10 minutes with no accessories on - you have a current draw issue....
Most modern alternators are pretty robust - I'd bet on a ground issue as the culprit....
Have you taken a failed alternator to real alternator repair shop to see what the problem is with the alternator?
I use a one man alternator/starter repair shop and the cost was very reasonable on my 1985 Corvette alternator.
He let me watch him which I liked doing. I took it to him for the work.
1984z51auto hit the nail on the head. What is the failure mode - regulator or something mechanical in the alternator. Have all the rebuilt alternators been from the same place ???
Assuming it's the regulator that's failing, you can do some simple stuff yourself. In addition to checking that the grounds are all good - I'd suggest doing a little diagnosis. Try to borrow an inductive (clamp over or clamp around) current measurement meter that will work on a DC supply (they exist but are significantly more expensive and therefore less common that units that read AC current only). Put that around the alternator main output line, start the car and see how it behaves - with no other accessories on - the car should not need more than about 5 - 10 amps to run - so anything above that is battery recharging. The current required to recharge the battery should diminish fairly quickly.... If you're seeing 20 or so amps after about 10 minutes with no accessories on - you have a current draw issue....
Most modern alternators are pretty robust - I'd bet on a ground issue as the culprit....
All the alternators are from the same place since i have lifetime warranty. I will trace the ground to make sure the wire is intact and making a good connection. Thanks for the help
Have you taken a failed alternator to real alternator repair shop to see what the problem is with the alternator?
I use a one man alternator/starter repair shop and the cost was very reasonable on my 1985 Corvette alternator.
He let me watch him which I liked doing. I took it to him for the work.
No i have not, but ill look around for one and give it a shot.
Have you taken a failed alternator to real alternator repair shop to see what the problem is with the alternator?
I agree. A good shop should be able to verify that the alternator is built right, and that the internal components are well matched. Here is the test report on my '84 alternator that I installed 10 years ago. This is a standard 108 A. unit, which put out a solid 145 A. @ 6,000 rpm. The bottom curve confirms that the rectifier diodes meet spec, and are well matched, which says that one diode isn't carrying excessive load, which would cause overheating and a short life.
Is there a possibility that you are charging a dead battery with your alternator? You should always use a battery charger rather than your alternator. Alternators are not intended for charging dead batteries, and that will overheat your alternator!
Last edited by Hot Rod Roy; Jan 26, 2016 at 12:24 AM.
I agree. A good shop should be able to verify that the alternator is built right, and that the internal components are well matched. Here is the test report on my '84 alternator that I installed 10 years ago. This is a standard 108 A. unit, which put out a solid 145 A. @ 6,000 rpm. The bottom curve confirms that the rectifier diodes meet spec, and are well matched, which says that one diode isn't carrying excessive load, which would cause overheating and a short life.
That was in the box with your purchase or part of a "for hire"? There are remans sold with a similar printout packaged with the product. This type of test isn't really very readily available at most "walk in" facilities.
The 7290-6 looks like it could maybe have been a test done on a specific replacement part # vs. a "carry in" for testing OR they used a typical 108A as a "spec" in the software to compare.
That was in the box with your purchase or part of a "for hire"? There are remans sold with a similar printout packaged with the product. This type of test isn't really very readily available at most "walk in" facilities.
You are right (as usual). I purchased this from a reman facility, and upon my request, I was able to review the test specs for several alternators, and was allowed to select my favorite. They were serialized, and all had different test results.
I only provided this information as an example of what can be done, and what the test results of a good alternator should look like. It IS possible to get good remanufactured parts!
(my 2-cents, FWIW) I hope we're not getting off track here. if the OP has gone through 5 alternators within a year, the problem is not with the alternator(s), but something electrical within the car itself. the odds of 5 bad alternators is about the same as winning the lotto. first thing I would do is check the battery condition, battery connections, grounds, especially battery to engine block, and clean and secure all connections. if the problem persists, a trip to an automotive electrical shop may be in order. personally, and from the limited info i'm reading, i'd check the braided ground wire from the battery to the frame to engine block. electrons are funny things - if there's not a good ground, current will seek out another path.
I suggested a "for hire" to the OP for a couple of reasons. It needs fixed and although he mentions the replacements have all been accommodated by the AP (he didn't mention which) I believe that all of the AP's "LIFETIMES" have been restricted to the FIRST REPLACEMENT, it certainly varies state to state, vendor to vendor and there may be some "grand-fathered" situations but maybe at his next request they could maybe "point towards the door".
I mentioned "could've and would've" and it really seems the OP has little interest. He's now at least asked so maybe he'll revisit with some things he's done.
I can't imagine an '84 that doesn't need some wiring improvements/replacements. The mid-eighties harnesses have all seen better days with insulation shrinkage, moisture/corrosion intrusion etc.
I hope we're not getting off track here. if the OP has gone through 5 alternators within a year, the problem is not with the alternator(s), but something electrical within the car itself.
The good grounds include the grounding of the alternator case. If the red output wire of the alternator is carrying 100 A., this 100 A. must have a complete circuit, which is thru the case of the alternator and thru the alternator mounting bolts and bracket, to the block. These connections must be clean and tight, too! The internal regulator won't work right if this ground path is poor.
I have always used a ground wire from my alternator case to chassis ground for this reason. Maybe my 10 year good alternator experience has something to do with this! (Much better than 5/yr!) WAG only!
If your going to let the battery get low and or depend on it to charge at low rpm's a good bit then the cs 144 upgrade is the way to go. Charges at idle perfectly and will last a long time under most conditions.
...thru the case of the alternator and thru the alternator mounting bolts and bracket, to the block. These connections must be clean and tight...
, and I might add, "...and from the block to the chassis, and to the battery! " ditto on the clean and tight thing. probably not a bad idea, and personally I've never done it, but, I have seen someone, like you, run a (braided) grounding jumper from one of the alternator mounting bolts, directly to the chassis. not sure if he was specifically grounding the alternator case or adding a secondary, engine block ground though - ???
, and I might add, "...and from the block to the chassis, and to the battery! " ditto on the clean and tight thing. probably not a bad idea, and personally I've never done it, but, I have seen someone, like you, run a (braided) grounding jumper from one of the alternator mounting bolts, directly to the chassis. not sure if he was specifically grounding the alternator case or adding a secondary, engine block ground though - ???
Some you've seen are likely OE and NOT added on.
Braided straps were used for years for grounds from engine to frame and even from the air cleaner stud to the cowl/dash panel to assure good grounding of the engine. I maybe still have a few.
They were actually intended for "radio suppression" and I believe all C3's or most got them. Most A-body GM performance cars got them and many were dealer added for the suppression on others.
The easiest install would likely be to buy your own ring terminals, the braided material and construct as you like. Tinned copper might be the choice now. OE were NOT.
Originally Posted by crowz
If your going to let the battery get low and or depend on it to charge at low rpm's a good bit then the cs 144 upgrade is the way to go. Charges at idle perfectly and will last a long time under most conditions.
If there's no "add ons" that increase the required output these could be considered over kill. Depending upon the talent of the person installing the addition of can get challenging. The availability of the "ideal alternator" brackets might challenge some L98 installs.
"LD85" asked about a CS130 to replace a 17SI one time. I answered his question and asked why, "coupeguy2001" busted me and then blamed "a full moon" maybe and explained why the CS144 was an easier install for a 17SI on the '84 or '85.
Thanks everyone for the help. I found the problem. Like most of you said it was probably a ground or a wire running to the starter. I took a look at the starter and saw a burnt wire that was corroded so bad it broke. I fixed the connection and started the vette. My voltage shot up to 14v, again I appreciate everyone's help.
Thanks everyone for the help. I found the problem. Like most of you said it was probably a ground or a wire running to the starter. I took a look at the starter and saw a burnt wire that was corroded so bad it broke. I fixed the connection and started the vette. My voltage shot up to 14v, again I appreciate everyone's help.
That's a "hint" to do all of the checks at all of the ground locations and all of the + connections involved in the system. It's good to see you post back. In the links in my first post there's some very basic checks with very inexpensive tools. You might want to use some of the info there and do your checks. It seems you're maybe to quick to rely on the Voltmeter. I'd still consider a "load test" as a "for hire" on a 30+ year old system. That one wire isn't "likely the only".
That's a "hint" to do all of the checks at all of the ground locations and all of the + connections involved in the system. It's good to see you post back. In the links in my first post there's some very basic checks with very inexpensive tools. You might want to use some of the info there and do your checks. It seems you're maybe to quick to rely on the Voltmeter. I'd still consider a "load test" as a "for hire" on a 30+ year old system. That one wire isn't "likely the only".
That's a good point. I'll get it checked out, thanks for the help.
Problems with alternator
