C5 Alternator problems

Took the car out for a ride today as I had some errands to run, and figured it was a nice day to take out the C5Z. Not long after leaving the driveway, I noticed a message flashing on my DIC, saying "SERVICE ENGINE SOON". WTH? Then I noticed the ammeter fluctuating all over the place, and as the needle settled at around 13.5 volts, I was able to clear the message, and everything seemed to be OK.

Drove up into the west side of Tallahassee to Lowe's and Home Depot, and not a peep out of the DIC. But on the way home, I noticed the ammeter started to fluctuate again, and the needle dropped down to what appeared to be 11 or 12 volts. Then the DIC flashed the message at me again. Uh oh... But yet again, the ammeter straightened out and the needle got above 13 volts. Still, making a beeline for home, just in case.

But as I got closer to home, I decided to monitor the battery/alternator voltage and the voltage reading seemed to be creeping below 12 volts. Normally it has been running around 14 volts, so something was amiss. As I was heading home, I was thinking I had an alternator problem, and if this kept up, I was soon going to be running strictly off of the battery. So I started sweating it a bit. Literally. Turned off the AC fan, turned off the radar detector, and started crossing my fingers. If the alternator quit completely, I still had longer to go to get home than I would have liked. Was praying at the intersection of 267 and 319 that the traffic light would remain GREEN for me so I wouldn't have to stop and waste what could be precious moments of driving time.

Anyway, I was able to make it back home OK, but by then the voltage reading had dropped down to around 11.3 volts And the DIC wasn't happy, neither. Obviously not low enough to drain the battery on me, but still, apparently the battery was not being charged up, and certainly the car didn't seem to be running on the alternator juice.

Since I have been able to keep the battery charged up OK with a battery tender, I'm leaning towards the alternator being the problem. I do have one of those battery/alternator checking tools, and according to it, the battery is fine at 12.5 volts, but the alternator while running the engine wasn't even registering on the idiot lights.

Of course, I did kill one of my battery tenders a week or two ago when I hooked it up to the C5Z, but not sure what that is all about. Fortunately the brand I have warrants the things for 10 years, so I was able to get a free replacement.

So I figured it is time to buy a new alternator. The one I have been currently running is one of those rebuilds you get at Advance Auto or Autozone. Held up OK for a few years for me, but I wanted to get a polished alternator this time for aesthetic reasons. Can always use some more bling underneath the hood. What I found was a 145 amp polished aluminum model from Tuff Stuff sold through Summit Racing, and this one has a clutch on the pulley, instead of the straight pulley on the current alternator I have. I've been reading that these are finding favor on vehicles to help with stress on the serpentine belt during deceleration. So what the heck....

Only thing that is potentially going to be a wrinkle here (that I know of now, at least) is that the current alternator is very VERY close to the coil sitting above cylinder number 1 on the valve cover.






This COULD be an issue.

But hopefully the new alternator won't be too fat back there to fit where the old one is located. Really only one way to tell, I guess.

Oh, on the bright side, not a peep out of that drivetrain noise the entire time.

I know that sucks for you but honestly, electrical components have gotten much more reliable than what we had in the 70's. I remember working at a Chevy dealer in the 80's when the cars started having computers. I just knew it was time to go into the wrecker business cause there was no way these electronics were going to hold up. They surprised me though. Even with those early, crude computers of the day, they were not as bad as I expected. And you seldom need a starter or alternator anymore. But hey, you wanted a chrome one anyway! :dancer01:

Yeah, I used to actually have a chrome plated alternator way back when, but it didn't last long. And the plating was pealing off of it. That is why I would prefer polished aluminum this time.

There might be a solution if I have a clearance problem, though. Back when Aaron Scott was working on my C5Z, he indicated he was having ignition problems and recommended that I replace the MSD 82858 coils I had on the engine with regular stock LS6 coils. Which I did. Because I trusted him at the time. But with hindsight now, perhaps those coils I have sitting in a box are perfectly fine. I looked them over today, and heck, somehow they sure got scuffed up on one side, so I have no idea what they have been through.

Anyway, I will attach photos below, but the place where there might be a clearance problem with the stock LS6 coils, might not be so with the MSD coils. Since I have both, I can certainly check that out when the alternator shows up. Replacing the coils isn't any big deal, so if the new alternator fits with the MSD coils, and the coils work fine, then problem solved.

So we will just have to see what happens.

Well, that didn't go as well as I had hoped.

That Tuff Stuff polished alternator I ordered from Summit Racing was drop shipped directly from Tuff Stuff and showed up today (Thursday). I didn't get a real warm and fuzzy feeling when I opened up the inside box (it was double boxed, to their credit) and saw that the alternator didn't have much to keep it from bouncing around in that box. Actually punched a hole through one side.




The next thing I noticed is that the plastic cap on the back of the alternator was loose. Well, the two threaded studs holding it in place didn't have the nuts installed that would have done that.







Or maybe they it was held tight in place by crimping on the studs and rolling around in the box during shipment just loosened them up. Regardless, not a real good impression.

Well, the icing to this cake was when I started looking at the actual polishing job itself. Well, NOT impressed!



















I also noticed that polishing compound appeared to still be in small nooks and crannies in the alternator housing, which meant that it was not cleaned off properly to remove the compound. If that wasn't quite enough, I also noticed what appeared to be polishing compound on the windings INSIDE of the alternator.



Which to me indicated that this thing was NOT taken apart to be polished, and was polished as is as a completed unit. Well, heck, I could have done that myself if I wanted to ruin a perfectly good alternator by getting polishing compound all inside of it. Thanks, but NO thanks.

So I contacted Summit Racing, sent the above pics to them, and told them what I thought about this junk I was sent by Tuff Stuff. They immediately sent me a UPS return tag, and I have that alternator all boxed up to take to a drop off site tomorrow.

Heck, I didn't even try to see if it would fit on the engine. I just did not want to waste my time mounting it just to take if off again to pack up to ship out of here. Maybe I should have done that, but honestly, I was pretty pissed off by then.

So I just ordered a plain jane "limited lifetime" warranty alternator from Advance Auto. Maybe one of these days I'll try my hand at taking apart one of the old alternators I believe I have laying around here, and see about rebuilding it. While it is apart, I can do my own polishing if I feel real ambitious. I certainly couldn't do an worse than what I am seeing from Tuff Stuff.

While I was waiting for this alternator to show up, I was looking real hard at what options I would have available if that #1 ignition coil was in the way of the alternator mounting up properly. And options were pretty slim.

First off, the MSD coils I already have from several years ago might work, but come to find out that these were made back when MSD was having a lot of problems with quality control from the place making them for them. These all have the part number of "8245" which has since been superseded by the part number "8285". Apparently the 8245 coils were made in the USA by a company that had some issues, whereas the 8285 coils are being made in China which is producing a much better quality product. Go figure.....

So it appears if I needed to use the MSD coils for fitment issues, I would have to buy a new set. At the tune of $620. :dead: Plus there is also the issue that apparently the MSD coils tend to draw more current from the ignition wiring harness, which is recommended to be fixed by utilizing an additional wiring harness (MSD part number 88867) that provides more current to the coils. That would be another $50.

While looking at coils, I noticed that the ignition coils for the LS2/3/7/9 engines are shaped in such a way that they would completely solve the clearance issues I might be having. They are nearly straight up and down on the left side of the coil mounting holes. Seemed like this would be the solution for me, but for a couple of snags. For one, the mounting holes are spaced differently from the coils for the LS1/6 family. So to make them work, it looks like I would need different valve covers. Of course, the valve covers I have were modified by Aaron Scott to put a breather between the two covers to relieve pressures when the engine is under boost conditions. Now that is bad enough, but then there is the issue of ignition dwell timing. That is the amount of time that a coil is drawing current through the primary wiring and controls the length of time of the actual spark through the spark plug.

As best I can tell, the dwell timing is different between the LS1/6 family of ignition coils and the later generations of engines. I don't know how much between the LS2 thru LS9 generation, however. But suffice to say, that my using those later generation of coils would mean dinking around with the tuning in order to change the dwell timing in the tune. I actually sent out feelers asking people about this, including Mike Carnahan, who originally helped me with the tune on the C5Z, and have yet to get any responses from anyone. So that would mean I might be shooting in the dark if I wanted to take that path.

So, right now, the best path for me seems to be to just find an alternator that will fit and call it a day. If the one I ordered from Advance Auto doesn't fit, I will have to pull off the old one and take it somewhere and say "I need an alternator just like this one" and see how that goes.

Or perhaps there is someplace nearby that will actually rebuild my old alternator. Assuming I look into this and it's not something I want to tackle myself.

Anyway, been another learning experience looking into this stuff. :crazy03:

Jerry's Auto & Industrial Electric Service And Parts
317 Blountstown St, Tallahassee, FL 32304
(850) 575-7464

I've used them before, real nice folks. Call ahead and see if they can do it while you wait. They rebuilt the starter on my V several years ago and the alternator on one of my trucks.

These guys are a dying breed. It's very difficult for them to compete with China when it comes to pricing. The livable wages here and there are much different. And of course all the parts used to assemble the starters, alternators, etc. come from where? You guessed it, China. But you'll be pleased with Jerry's. They've been in business there for many years. Turn off of Capital Circle right onto Pensacola and then left onto Blountstown Hwy. You'll see the building on the right.

in the 2nd picture of your first post, does the red wire have a bare spot? also, when my alternator went out, i got one from autozone. immediately got the charging system fault. alternator worked. problem is the valeo alternator the corvette comes with ignites at 1600 rpms. the ones you get aftermarket ignite at 2200 rpms. so don't lose your oem alternator. ended up getting mine fixed at a local alternator/starter repair shop here.

85vette said:

Jerry's Auto & Industrial Electric Service And Parts
317 Blountstown St, Tallahassee, FL 32304
(850) 575-7464

I've used them before, real nice folks. Call ahead and see if they can do it while you wait. They rebuilt the starter on my V several years ago and the alternator on one of my trucks.

These guys are a dying breed. It's very difficult for them to compete with China when it comes to pricing. The livable wages here and there are much different. And of course all the parts used to assemble the starters, alternators, etc. come from where? You guessed it, China. But you'll be pleased with Jerry's. They've been in business there for many years. Turn off of Capital Circle right onto Pensacola and then left onto Blountstown Hwy. You'll see the building on the right.

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I'll keep this in mind if that alternator I have on order from Advance Auto won't work for me. Thanks for the tip.

mrr23 said:

in the 2nd picture of your first post, does the red wire have a bare spot? also, when my alternator went out, i got one from autozone. immediately got the charging system fault. alternator worked. problem is the valeo alternator the corvette comes with ignites at 1600 rpms. the ones you get aftermarket ignite at 2200 rpms. so don't lose your oem alternator. ended up getting mine fixed at a local alternator/starter repair shop here.

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Yes, I noticed that too when I looked at the pictures. Not sure when nor how that happened. I'm intending on dabbing a bit of Plastidip on it when I replace the alternator. Which reminds me, I wanted to order some white and red Plastidip. I have black and white (spray only), but no red no white in the "dipping" variety.

As for my oem alternator, I'm not sure I still have that around, as I replaced the alternator a LONG time ago. But seems to me I do have a couple around here somewhere.

As for the ignition rpm, from what I have been reading recently, I thought that was controlled via a signal by the PCM?

Oh, one additional note concerning the thought of using the LS2/3/7/9 coils on an LS1/6 ignition system. The plugs on those coils are different, too. The older coils have a rectangular plug where the newer ones are more oval looking. There are individual adapters available for each coil (8 needed), or you can get the two harnesses (one for each bank of coils) as the plugs that the two harnesses themselves plug into are the same for both style coils.

As for the dwell timing issue, it appears that the dwell for the LS1/6 coils is longer than for the LS2/3/7/9 coils, so without changing the dwell in the tune, you run the risk of early failure of those newer coils just plugged into the LS1/6 system.

But that being said, it appears that some people have gotten some noticeable torque gains by increasing the dwell timing. But as mentioned, this could shorten the life of the coils as a result. So it could be that some people who claim to have gotten HP gains by going to the newer coils are correct, but the life of their coils might not be what they will appreciate much.

For what it's worth, the previous owner of my V put MSD red coils on it. I don't know what part numbers, but I put over 70K miles on them and had no issues. I don't know what installing them entailed as far as dwell etc. but I had no ignition woes.

Rich Z said:

Yes, I noticed that too when I looked at the pictures. Not sure when nor how that happened. I'm intending on dabbing a bit of Plastidip on it when I replace the alternator. Which reminds me, I wanted to order some white and red Plastidip. I have black and white (spray only), but no red no white in the "dipping" variety.

As for my oem alternator, I'm not sure I still have that around, as I replaced the alternator a LONG time ago. But seems to me I do have a couple around here somewhere.

As for the ignition rpm, from what I have been reading recently, I thought that was controlled via a signal by the PCM?

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the exciter in the alternator is what does it. once it reaches rpm speed it sends the signal to the computer. been there, done it. the reman alternator i got had a test sheet showing output testing and showed when it excited. sure enough it wouldn't not turn on until i hit 2200 rpms. kept getting the charging system fault on the dash. so had mine rebuilt and gave theirs back.

85vette said:

For what it's worth, the previous owner of my V put MSD red coils on it. I don't know what part numbers, but I put over 70K miles on them and had no issues. I don't know what installing them entailed as far as dwell etc. but I had no ignition woes.

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I think the 8285 MSD coils would work with the stock dwell of the LS1/6 system without alterations, but the additional wiring harness MAY be necessary in some instances. MSD has indicated that *some* vehicles may have insufficient gauge wire in the stock ignition harness to carry the current their coils need. So it sounds to me that if you have problems with the coils, then adding the harness would be recommended. That being said, I have read accounts of people putting in the MSD harness even with stock coils to help provide more current to the coils. :shrug01:

mrr23 said:

the exciter in the alternator is what does it. once it reaches rpm speed it sends the signal to the computer. been there, done it. the reman alternator i got had a test sheet showing output testing and showed when it excited. sure enough it wouldn't not turn on until i hit 2200 rpms. kept getting the charging system fault on the dash. so had mine rebuilt and gave theirs back.

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Well, I don't think I have hit up against that particular problem. At least not yet. I have had at least three alternators in the C5Z since I bought it, and never got that sort of error message. Since the car will cruise on the highway in 6th gear well below 2200 rpms, I would think the battery would gradually discharge and such an error fault would manifest itself. Just cruising down route 95 at the speed limit would be well under 2200 rpms, so if the alternator is not charging the battery the entire time, I would imagine the battery would go dead in pretty short order that way. Heck, I would imagine that most of my driving is actually below 2200 rpm.

Wouldn't this show up on the ammeter while driving? When my current alternator was working OK, it would normally show 14 volts regardless of what speed the engine was running. Even at idle just sitting in the garage. Wouldn't that be telling me that the alternator was pumping juice to the battery regardless of engine speed?

Now you have me interested in looking into how this actually works. I would have thought the circuitry would monitor the battery voltage, regardless of engine speed, and spark up the alternator when electrical demands needed the juice. Sort of how a trickle charger works.

But I am guessing that there has to be some lower limit in the speed the alternator is spinning when it cannot deliver the amps necessary. Which then brings up the question as to whether a higher amperage rated alternator would be able to deliver that lower limit amperage at a lower rpm speed than a lower rated alternator. For instance a 145 amp alternator could deliver, say 50 amps at 1200 rpm (just pulling numbers out of my hat) whereas a 110 amp alternator might need 1600 rpm to deliver the same amperage. Honestly, I have no idea. Might be the complete reverse. :shrug01: :shrug01:

The alternator from Advance Auto got delivered today, so I went ahead and installed it. Easy enough to do. Not least of which was because I didn't have a clearance problem with the coil above cylinder #1 like I was worried about. It's REAL close, but it is OK.









Cranked it up and this alternator is putting out 14+ volts to the battery, so that should keep it charged up OK.

Of note is that the paperwork included with the alternator indicates that it is putting out 61 amps at idle engine speed. Not sure what exactly the engine rpm speed is for that figure, however. I believe the stock alternator puts out 110 amps, so this one at 145 amps should keep the electrical juices flowing sufficiently.



I actually thought I would be getting an alternator with a clutch pulley on it, but oh well. Pics showed it that way when I ordered it. But I guess Advance Auto isn't exactly on the ball. For instance I didn't get the tracking number email from them until a good 8 hours after it had already been delivered.

Also, while I was at it, I pulled out the fixed tension serpentine belt tensioner I put on several years ago. Put a stock spring loaded tensioner back in. I noticed that the serpentine belt tension with this spring loaded one is noticeably less than what the spec tension was for that fixed one at 25 ft./lbs at the tensioner wheel.

Guess this means a test drive is in order tomorrow or the next day.........

Looks better than the other one.

Yeah, I think so too. Wish they hadn't put that sticker on top of it, though. On the alternator I had on before this one, they had stickers on it too. When I tried to remove them, it made the word "VOID" or some such visible, so I just left them. Heck, now I'm wondering if I had a lifetime warranty on that older alternator. Like I would remember something like that a few years later.... :shrug01:

Well, at least I didn't need to spend $620 on a new set of ignition coils right now. Of course, I have been reading about the multispark capabilities of those MSD coils, and wondering if that would help with the unburned gasoline smell I get at idle. I never did get the open loop tuning at low RPM the way it should be, and I can smell it is running a bit rich until closed loop kicks in.

Maybe if I get a big fat social security raise from the government for doing such an excellent job at being retired I'll think about buying a set of those coils. :hehehe:

While I had the car running making sure the serpentine belt was positioned correctly, I heard the AC compressor clutch clicking on an off at idle. So I think I do have to check those pressure readings again, and likely will need to add more freon (or whatever it is called these days). The air blowing out of the vents is plenty cold enough, but I thought a cycling compressor was a sure sign of low freon.

They won't run constantly but will cycle when head pressure gets high enough but that's normal. But they will also cycle when it's low on freon. So still would be a good idea to check the freon level.

The light on the button for the AC will often flicker on and off when I am sitting at idle. Been doing that for a while. It cycles about every 5 or 6 seconds. Of course, I can only hear it when I am standing in front of the car. Too noisy to hear anything anywhere else.