dbrochard

iTrader: (3)

Hey guys, imagine this. You finally come home from college and cant wait to terrorize your local family neighborhoods with your thirdgen, but wait! A strange electrical issue has appeared, and after two dead alternators you realize it is a short circuit that is doing some damage to your electrical system. After replacing the alternator(s) and driving the car with the ACC fuse pulled (It would change the resistance between the battery terminals when disconnected, it seemed to be it) you have now killed the third alternator in less than 100 miles. Here's the breakdown more simply of what the issue is

-With the battery disconnected, 1.1 ohms of resistance is measured between the two cables. This is a very small number and theoretically should be infinity, since there is an infinite amount of resistance between the positive and negative cables since they, well, should not be contacting each other at all.

-With ALL of the fuses pulled, the car now shows 70 ohms of resistance between the two cables. By plugging the TAIL fuse back in, the resistance drops back to 1.1 ohms

-No wires appear to be damaged or broken, even though something clearly is.

-No fuses were blown

-Several days ago, before driving it and killing alternator #3, the car would show 30,000 ohms (safe enough) of resistance between the cables as long as the ACC fuse was disconnected. With it connected, it would drop down to 20-250, depending on whether or not the doors were open or the light switch was turning on the interior lights.

I would greatly appreciate any guesses or insight or advice on fixing this, I just want to drive my car again. It worked fine when I came home 3 weeks ago, it was stored in a mice-free garage.
The tools I have available are a multimeter and a short sniffer, but it does not seem to offer any conclusive data on the issue. Unless I am somehow using it wrong

dbrochard

iTrader: (3)

The car is a 1991 Camaro RS, vin E, 305 5 speed, wiring is mostly stock aside from a stereo system, added power mirrors, and headlight relays, all of which have been checked and are ok

PaulyC

Ill be honest, Ive never tried nor would I suggest testing resistance between the battery cables to troubleshoot this. Not that it will cause any problems, just that it isn't going to tell us much. When you say killed the alternator, what exactly do you mean? I assume it is no longer charging but be as specific as you can. When you replace with a new one are you verifying it is functioning correctly? You should see 14+VDC running voltage if all is working right. I would also ask to check parasitic draw by placing a DMM or ammeter between to positive post and cable (don't try to start the car with the meter connected). Also, have you had the battery load tested?

dbrochard

iTrader: (3)

When I say killed the alternator, what I am referring to is that the alternator was charging the car to 14 volts while running, but then after driving it for a little bit, say 25 miles, each of them stopped charging and never charged again on the following start ups. I tested each one and yes, they were functioning correctly at first. I haven't tried testing between the post and cable, but that is a good idea as long as I can do it in a way that won't damage the multimeter that I have. The battery hasn't been tested, but I tried two different batteries, both of which work when plugged into my 88 iroc so I don't think there is anything wrong with those.

How would you recommend going through this to troubleshoot? I have read forums but I feel that my particular case here is very strange and simple youtube videos don't go this far in depth

PaulyC

That’s what I thought, ok so if there is a short you will see an amperage draw on the battery and eventually drain it. Since you didn’t mention the battery being discharged overnight or over time I’m going to conclude that probably isn’t an issue, correct me if otherwise. Also, since there are no blown fuses or other items not functioning (again correct me if otherwise) I am leaning away from a short. The only symptom is a non charge after a short period of time. The resistance test can be misleading depending on equipment installed like a security system and other items that are hot at all times. So even with an amperage draw test you will most likely see some draw but very low <1 amp. If it is higher than that, I’m still on the fence. Reason being, even a quick intermittent dead short from a shaking around while driving will blow a fuse and probably a fusible link. If these alternators were under warranty, did the store bench test them when they were returned?

dbrochard

iTrader: (3)

Yeah the battery is not being discharged at any noticeable rate. The first two alternators were the one on my car since '04, and then a used one, so no warranty. The new one does have a lifetime warranty but I have not brought it back to be tested again or replaced. But it was fine when it was bench tested when I bought it.

GeneralDisorder

iTrader: (1)

Where are you getting these lifetime warranty "alternator" (s)? That's usually complete junk.

Resistance between the battery terminals is meaningless. You are testing through computers, etc.

I haven't had too bad of luck with the AC Delco new (China) alternators. You probably will have to go online or to a local repair shop that can order from Worldpac, etc.

Here's the one I used on Amazon:


It sounds like the original alt just died. And the used replacement was a gamble. And now you are experiencing the hell of chain auto parts store electrical parts. Honestly I doubt it's the car's fault. You are using sub-standard parts.

You want a decent alternator it's going to cost...... https://www.dcpowerinc.com/

About $469 for a 180A unit from a reputable performance manufacturer.

GD

dbrochard

iTrader: (3)

I just can’t accept that 3 alternators die within a matter of weeks. The first was on the car for 14 years so it was old, the second was used but looked pretty new, and yes the third was from Autozone. I just doubt that 3 alternators would die that quickly out of coincidence or being sub par parts.

Where would you recommend measuring resistance then?

PaulyC

I've had autozone alternators fart out in days or not work at all. I will no longer go to autozone unless there is no other option and even then I will contemplate going without. Their alts really are trash, just return it for a refund if you can and get a quality alt so that isnt a variable.

GeneralDisorder

iTrader: (1)

You can't test anything for resistance that would be meaningful as pertains to causing damage to an alternator.

You can load test the battery and maybe if it's consistently low and being drained it would be putting an excessive load on the alt and overheating it - potentially damaging the electronics. But that would generally manifest as slow cranking and/or having to jump it, etc.

The original alt was 14 years old. It was due. The used alt was maybe newer but possibly of the same poor quality as the Autozone trash. Also if it sat around it may have had corrosion on the brushes and rings, or a bearing issue, etc.

Autozone is the WORST place to buy any electric parts.

Look I own a shop - I see this EVERY day. I have been in this business for many years, and I'm a certified military trained generator technician and I used to work for a Generac dealer. I know something about electrical systems.

Put in a quality alternator and a quality battery. Change the battery cables and ensure they have good clean connections to the starter and the engine/frame, and check for any parasitic draws. Beyond that if it starts, runs, and the alternator isn't 3000 degrees from a massively oversized stereo or something.... your problems will be solved.

GD

travsirocz

Testing resistance between a unhooked battery is not a valid test. You have a lot of series circuits that will will bring the resistance down. Ohms law. The best way to check for a large draw is with an amperage meter inline of the negative battery post. Should not be greater than .05 amps. Many part store rebuilt alternators are not very reliable. Try to find a local rebuilder or buy new. A defective battery could possibly kill an alternator but you should have other issues present as well like a dead battery or slow crank.

I would also do a voltage drop test of all of the main battery cables and alternator power lead.

dbrochard

iTrader: (3)

Ill try measuring the amperage between the negative battery post and the cable

I understand and agree that Autozone stuff is probably not that high quality, but I can’t go buying a new alternator after 3 died in such rapid succession unless I know for a fact that it is the problem. Both batteries I’ve tried work fine in my 88, so I don’t think they are a problem but I could be wrong.

I’ll look into how to properly do a voltage drop test as well

travsirocz

With your voltmeter, measure the voltage between battery positive and back of alternator, battery negative and body, battery negative and engine. You will want to do this with engine running and loads on like fan and lights. Should see no more than .5 volts.

GeneralDisorder

iTrader: (1)

Do this with the car OFF ONLY! You will burn out the fuse in your meter if you try to pass the full vehicle load through it.

Or you need a DC amperage clamp (or a shunt to bring the amperage down to less than 10A - which is likely to be the max your meter can handle, but you are unlikely to have this or easily obtain it).

These work pretty good for the money:


Honestly though - you just need to clean your cables, make sure you have a GOOD battery, and buy a quality alternator. You are WAY overthinking this. The car just can't really do what you think it's doing (kill alternators).

GD

travsirocz

Yes agree, key off doors closed, hood light disconnected. Amperage clamps are not the best or accurate option for low draws like this, but they will measure bigger draws well.

NoEmissions84TA

iTrader: (1)

Starters and alternators are no longer completely rebuilt/remanufactured as in the past. Now rebuilders determine the bad component(s) and replace ONLY those.
Then clean it up and throw it back in the box for resale. You must buy NEW to guarantee all new parts.

I agree with GD's diagnosis above. And your 14 year old alternator probably only needed new brushes.

dbrochard

iTrader: (3)

With my clamp on ammeter (Greenlee cmi 600) I measured 0.09 amps on the negative cable, and by using the alligator clips and measuring between the post and cable I measured 0.1 amps

This was done with the doors closed, hood light unplugged, and also all the fuses are still unplugged.

I havent done a voltage drop test while it is running yet

travsirocz

Keep your meter connected for about 15 min and check again to make sure it doesn't drop more. If you are still at .1 of an amp, that is too much and will cause a dead battery over a few days. This isn't going to wreck your alternator. My money is still on defective remans.

dbrochard

iTrader: (3)

I’ve been leaving the battery disconnected so it doesn’t die when I’m not testing something. The first alternator died during a heavy rainstorm so maybe water got somewhere it shouldn’t have, but the next two only lasted like 30 miles before dying and I just can’t believe that low quality remanufactured alternators would die under the same conditions that quickly without something else being wrong. Besides, the second alternator (which was used but new) worked for plenty of time in the previous car, and then once it goes into my car..... pretty quickly dies.

And i appreciate all the help by the way everyone, it’ll be really exciting to find out what the culprit was.

dbrochard

iTrader: (3)

I should also mention, the insulation on the output terminal of alternator #2 was melted. It’s gotta have some crazy amount of amps being demanded by the car when it’s running, so I’m gonna go test the amperage with the car running.

travsirocz

#2 probably had an internal short in the alternator. Alternators are only able to produce near their rated output. Before I knew better I went through 5 within 3 months. One had an internal draw, some didn't charge out of the box, and others failed after days or weeks.

GeneralDisorder

iTrader: (1)

This is a CLUE. But not to what you think. The melted terminal is a sign of a BAD CONNECTION, it really has nothing to do with the amount of amps. It has everything to do with too MANY amps for the available CONNECTION. A poor connection is like a really small wire. Even relatively small amperage will destroy small wire. Put 10 amps / 12v through some 22 AWG and see what happens to it. Much like small wire - a bad connection with a normal amount of amps will simply heat up and melt at the connection point.

As I have been saying from the START. Replace the alternator with new (not crap), and replace the battery cables and run a new lead from the alt to the battery +.

GD

travsirocz

I agree with this as well and should have been closely inspected. If the connection was clean and tight, there could have been an internal short or poor connection which generated heat that was transferred to the plastic from the alternator.

GeneralDisorder

iTrader: (1)

Yes - the bad connection could easily be inside the alt where you could not initially see it. I have had alternators burst into flames just from being run after sitting for half a year. I was troubleshooting a dead battery on a tow-in for a customer so naturally I fired it up on a jump pack to test alternator output - something inside the alt started glowing red hot. So of course I run around to shut off the engine and am immediately greeted by 12" flames leaping out of the alternator case (because the fan stopped blowing them out). I managed to blow out the flames and the car didn't burn down but I did have to clean out my shorts after $hitting my pants. I was in the parking lot with no fire extinguisher handy..... new shop policy is to take the fire extinguisher to the parking lot when jumping vehicles. Never thought I would have to make that rule!

GD

IROCZ1989

iTrader: (1)

Did you trace back those wires from the alt? On mine one is tied into the fan relays for key turn on and then goes all the way to fuse box through the c100 harness. It's not fused there but in a buss on one side of the fuse panel part of 3 fused items. It only live key on. Dont know if yours is the same as the 89tpi. Trace them back and see what you find..

John in RI

iTrader: (167)

What are you using "headlight relays" for in a 91 RS ??

Did you wire/install the power Mirrors by connecting them to the factory harness with NO modifications ??

What kind of a system did you install and where is it getting Power / Ground ?? Did you install and AMP or any other remote stereo accessory ?? Are you SURE the BROWN headlight signal wire and the GREY DIM circuit are wired properly. Is the YELLOW "switched" power wire and the ORANGE "hot" wire properly wired ?? First thing I would Disconnect the radio / stereo completely and re-test.

zegman

Several years ago I had the same thing happen with my alternator and my cooling fan also stopped working. Look at what IROCZ1989 said above about the wire that feeds both the alternator and fan relay. .Although my wire had voltage on a Digital Volt Meter there was not enough current to light a test light bulb. Ran a new wire and both problems solved.

IROCZ1989

iTrader: (1)

When your first got back and cranked it ,did it fire right up or did it just about start? If you have a constant drain on the battery and you are using the alt to recharge the battery the alt isnt going to last long. It cycles on and off to keep the battery topped off. If its topping off a low voltage battery and running the car you are asking it to do more than it has to. When idling what is the voltage across the battery? Should be 13.5 and up. Load test the battery of you think it's that. You added some relays in the system. So besides factory stuff you need to recheck your wiring. Like where did you get the key on 12 volts? Is the ground on the relay have a good contact. Where did you tap the 12 volt feeding whatever you put in. Is it fused? Basically the wire I mentioned before is a key on 12 volt wire that runs 12volt from the fuse box to the alt. It tees off into the fan harness to give 12 volt key on to the relay. It's not a fused wire. When you search A7 pin slot of guys just cut it out when doing a engine swap because its labeled as emissions/cold start in the helm manual. If you actually traced it , it's a benificial wire that can be used for 12 volt key on in the engine bay to wire any relay you want to add.

GeneralDisorder

iTrader: (1)

Exactly - if you have a draw it will toast alternators (especially cheap one's) trying to charge the battery. The Alternator IS NOT DESIGNED TO CHARGE YOUR DEAD BATTERY! It's job is to run the car and trickle charge the small amount of amps that you used to (quickly) start the car. That includes old/poor quality batteries that just get smacked into the dirt by the old long crank L98 tuning that has to see a million reference pulses before it injects any fuel.

QUALITY Alternator, QUALITY battery, 4AWG (or larger) COPPER cables and lugs. Clean, tight connections. Apply some terminal grease to keep them that way. And make sure you don't have a draw.

GD

dbrochard

iTrader: (3)

The mystery was finally solved (sort of). The first alternator died from some unknown reason, same with the second. When testing the voltage drop with the car running, I found that the car was producing 14 volts while the gauge in the car said it was about 12.5. Cleaned the contacts on the voltage gauge and now it is fine, and the third alternator (the Autozone one) is still alive after all. It is odd that the voltage gauge decided to start to malfunction at the same time as this, but I’ll ignore that fact until another problem comes up. Moral of the story: don’t trust the gauges and use another device to measure the voltage, as well as how many amps are being demanded. With my high beams on, interior lights on, stereo blasting with the subs all the way up, I only got it to draw 60 amps, which is a lot, but I think an acceptable amount for that alternator especially in short periods. Case closed, mystery solved, thanks for all the help guys!