Not saying that its not possible to over charge a system or get spikes or surges...Anything thing is possible and I'm sure the electronic systems on the C5 are pretty sensitive to voltage spikes...


I will also say that it sucks when you're sitting in traffic, fans are running, engine temps are heating up and voltage is dropping.... As voltage drops, fans run slower, engine heats up more...its a vicious cycle... It really really sucks when you're stuck in traffic and you're not sure what is going to happen first, either over heat or battery go dead from low voltage.... Several times I was stuck in traffic at night and saw 11.9v on DIC (really 12.3v at battery) and you see the lights getting dim. That was with a 30k mile Valeo 110 amp that normally charges fine until it gets really heat soaked and fans/lights are on.

So for me, there was no other option, find an alternator that is reliable, and do what it takes to make it work to keep the voltage constant, and hope for the best.

First:

I did my own version of the "big 3" with 2 gauge ground wire. I also added 8 gauge charging wire(w/10 ga fusible link) directly to the battery from the alternator. I also went through and cleaned all of the oem ground connection points and ground bus terminals.

Second:

I started with the Billettech and the first couple of rounds of bugs/fixes.. I drove it for a while with just letting it self excite at 2000 rpms, it worked but it was annoying...So in talks with guys at BT, they came up with the jumper plug. They also determined they could increase voltage output with a resistor in the jumper so after reporting to them what my hot voltages were and amp load, they dialed in the jumper wire to give me another .7v.

I've put about 4k miles on it with the Billettech and everything on the car works better.. Headlights and dash lights are brighter, fans runs faster.... It helps supplement for the voltage drops we see across the wiring harness for the pitiful size wiring that's in there. I get an actual 14.0v at the fan plugs which is nice.

I've had no issues with the BT alternator or the car since figuring out the fixes.. and as I mentioned, I religiously glance at the voltmeter on the dash and its always at 14.0. So I may not get a charge fault indication/code, and I could have a nuclear melt down of every computer system in the car.... But so far, so good...



My recommendation is to stick with a 170 amp alternator, I would not get crazy with the 250-300 amp alternators, I think in those cases, you are asking for electrical problems from way too much juice potentially hitting the systems unless you have something that's pulling a LOT of drain on it to consume that amperage.. Not too mention, the 170 amp alternators usually charge better at idle (where you need it) then the 200+ amp alternators.

 

ET, first of all, thanks for weighing in on this subject. Today I was sitting in traffic with my AC on blast and was reading about 11-12vdc on the dic. I have a automatic 2004 base coupe. I value your opinion immensely. Could you please tell me the highest rated but SAFE alternator I can put in my car. Should I just go with a stock alternator from GM or can I put an aftermarket on? What is the maximum amperage that is safe for my vehicle. Thanks so much!

 

mine never drops that low ????????????(Stock alt)

 

How many miles on the alternator? Does it seem to charge better when you first start it up? Reason for asking is, the decoupler can "fail" over time. Mine began slipping...more than it is supposed to. Could be your issue if you don't want to really go full on HO alt. Pull it off. Grab the pulley. Intentionally try to spin against the internals both ways. If you can see that you're "leaving the internals behind" fairly easily, slip, then your decoupler is probably shot.

 

Not correct, it is only 5 volts to "flash" the field.

 

Is do the "Big three" also a mistake then? Could this possibly cause issues with surging and poor electronic control? I am confused about what is okay to do and not. I currently have the Big two two1 gauge grounds, one from the engine to the frame and one from the frame to the battery. My voltage fluctuates between 14.2 and 14.1 at idle with a surge each time it drops .1 volt. I just had the balancer replaced with the ATI unit and the rockers, springs, and seals upgraded. Now its smooth as pie except at idle. is the Big Three a Bad Three? I though all grounds are good unless they are a loop.

 

Big 3 is a good idea

 

So I really need to add the alternator wire as well. How many amps should my fuse be?

 

IF you want to run a radio that requires a fire truck alternator, get a fire truck. Horses for courses. Not the hot rod way, but how much time and money do you want to step into?

When a design engineer tells me the computer will not understand voltages outside of its intended design , that is enough for me. But then I don't put light bulbs into receptacles that don't carry the correct ratings either. Call me crazy, I guess I have a thing about avoiding extra trouble in life, coupled with a deep aversion to electrical fires .

People that can understand and repair modern electrical systems in cars are hard to find. I wouldn't want to be trying to find a guy to fix a burned up C5 system. A non hack can make money more easily with other repairs. I had enough trouble finding a shop for a clutch repair . One might check for repair options before deciding to mod the electronics, it might be better in your area.

I suppose when the knowledgeable posters loose interest, the group internet mind will continue along the bigger is better line ,and that the cars will get a bad reputation , making cars like mine that will still run and have not had an electrical fire , notable.

 

I left GM 15 years ago... but right after my exodus from GM I still had inside contacts, which are all retired or dead...
there was a time when you could get the upgraded alternator from GM 145 amps. but it required a specific re-flash of the PCM, so the PCM would accept the higher duty cycle.. I'm not sure if that is still an option.
Bill aka ET

 

Great post. I just spend 30 minutes reading this entire thread and many guys are discussing the legacy and history of the c5 and what we should or shouldn't do to it.

All I was looking for was a post to see which alternator to buy, and what extra parts i need to make my sound system pump without dimming.

Looking for a 170 amp unut.

Has anyone tried the macman alternators? Or should I go with BT?

Also, do you mind for us noobies to explain The exact parts needed to make the alternator work as the OEM would. So basically as close to plug and play as possible. What's a jumper? Where can we get one?

Is there anything else needed?

I built a crazy fiberglass custom enclosure for my sub. That Baby is there to stay. Just not at the expense of frying everything else.


Any help is much appreciated

 

Pictures please

 

mechman is billet tech, same thing... mine is still working great

 

I realized that after I wrote the thing lol.

I think it'll need a self exciting thing. I've been told you choice can be disabled with a computer tune. 500$ later

 

I am going to jump in here... Knowing this system very well.. the system has a discrete circuit which measures the duty cycle. this discrete circuit has no interruptions or bypasses, and the resistance is measured, so it can't be altered... the algorithms are set to measure any fault or draw above 110 amps or 145 amps in a later car. So tell me how a duty cycle of 150 amps or 170 amps, will not trip the set point of the PCM giving you a fault warning.. unless of course you just ignore the warning. That's just like removing the oil pressure sender and Hope you don't loose any oil pressure. OK IM don't in this one
Good luck
Bill aka ET.

 

If you're saying that the system in its unaltered form can protect C5 owners from issues arising from ground faults, that's not true at all and if you're trying to say that it will even tell you if you have a ground fault in the electrical system, that too is false, so I'm trying to figure out what you're saying.

I don't know what you're calling a "back surge" or how you think that's going to occur with an aftermarket alternator when turning off the "charge fault" message. The alternator comes on and charges and no messages occur. Regardless of why the nag was put in place, it was a ridiculous idea that was removed in the 05 and later models.

I've seen engineers forced to come up with "something new and innovative" and it be a total flop before. It's what they have to do in order to justify their existence on the payroll. It gets sold to the upper management with each level bragging about their group's great idea so they can receive their bonuses for the year. I can't help but believe this is one of those circumstances.

Ive installed a handful of these alternators without issue. Bypassing the nag? You bet. The only thing the charge fault seems to have come from is when the alternator fails to fire up within the parameters set forth by the programming. I'll continue below.





Bill, I understand you're one of the engineers responsible for the C5 platform and have appreciated your input on some subjects, but this one I simply don't get.
If the algorithms are set to measure any fault or draw above 110 amps or 145 in the later cars, then how is it that a much higher efficiency, 6-phase alternator, working less to achieve it's output, triggers the message? Tell me how it matters whether you have a 110 amp alternator or a 320 amp alternator in a car. Just because someone has a 320 amp alternator does not mean that the alternator produces more current on any given car agreed? If the load of a given car under given circumstances is 80 amps, then bolting on a higher output alternator will still have 80 amps of output unless the output voltage is increased. Then and only then will the output current increase. If the message is designed to show up when output of the alternator ends up being exceeded beyond it's rating as you say, then why does it show up when the alternator fails to spin or excite? That's under-performing, not over as you say it's designed for.


I consider it ridiculous to compare eliminating a charge fault message to removing the oil sending unit. When you remove the oil sending unit, are you still magically able to read your oil pressure?

Eliminate the charge fault message and you're still able to read the PCM voltage through both the gauge and DIC. If the voltage ever gets too high, there's a separate message for that. If the voltage ever gets too low, you'll know soon enough and if the message came on a few seconds earlier to tell you that the alternator was under performing, you're probably still calling a tow truck just the same IMO.

I've worked on C5's for quite some time now and while an aftermarket alternator may not be necessary for everyone, it is for many. The increased voltage, especially at lower engine speeds has proven to be advantageous in many ways. Having sold close to 1000 of these now, I can say that only one of us has experience on the other side. I genuinely care about what I offer my fellow Corvette owners. I care to offer meaningful products that enhance the owner's ability to enjoy their vehicle without negative effects on the vehicle. Not one customer has ever or will ever incur any damage to their electrical system, solely from the installation of a Mechman alternator.

 

After rebuilding my engine and troubleshooting various issues along the way I noticed my voltage on the DIC is lower than I would like. When the car is warm with AC, Upgraded spal fans running, amplified stereo, meth system, gauges, etc. I'm seeing voltage around 12-12.5v. At this point I'm willing to shell out for a billet tech alternator if it will work. Can those still running one chime in with updated results?

 

mine still works great, no issues since I've had it... pm the guy that posted above you and he can get you setup

 

The voltage has been showing from the DIC. When I start the car and I'm not running AC or fans and it's cold see voltage around 13.7 as the car warms up I gradually see voltage go down to the high 12's with the AC on and the fans come one. When the fans go into high speed mode and the alternator get heat soaked I see even lower voltage on DIC. Haven't done the big 3 upgrade either.

 

I just got my car about a month ago and it came with a brand new rebuilt AC Delco alternator that shorted out while I was driving!!! Anyway I couldn't get it covered under warranty because I was the "second" owner of it. I was pissed. So I looked all over the web and I couldn't believe how expensive they were. I lucked out at Amazon warehouse deals where I picked up a Brand New alternator for under $70.00!!! Regular price is $178.00 but it's worth it. It fit perfect and is 140-145 amps. Now I don't know if you are running a bunch of power robbing things that warrents an alternator as big as you stated. Do you have a second battery? A huge sound system ect? I put mine in and it only took me about 15 minutes start to finish including disconnecting the battery. I charged up the battery to a full charge and then started the car. It's putting out 14.1 at idle. And yes this comes with the clutched pully! It also has a two year warranty. Much better than most. It's made by Premier Gear and the part number is 13969 and there's no core charge. And I'm a Prime Member at lamazon which means no shipping. It's been a week now and it's working great and still putting out more than that Delco rebuilt one. It's keeping the battery at full charge even if I only do short trips. I think that this is a great deal for a quality product. Even the way it's packed in expanding foam, is terrific. I can almost guarantee you this one will work perfect for you. Just passing along a great experience with great results. Good luck!
As a side note you don't want to have too much power/amps. Your system was meant to be run on the stock alternator which is 140 or lower depending upon the year and model. Power surgess are a killer for electronics.