Strange alternator behavior? 5.3L swap

[kingtal0n]

I've had this swap running for over a year. about 5 months ago I put a 525CCA (pretty large footprint) batt brand new in the car and didn't think anything of it since then.

Recently I've been having starter cranking problems. I attributed this to aging starter.
Then I accidently left my headlights on, completely killing the new battery.

Well I got it jumped, and drive it around 30 minutes to re-charge.
However there was very little charge in the batt after 30 minutes. I think the alternator is barely charging the battery.


I disconnect my batt. cable and the engine dies after a moment, also making me realize there is an alternator problem.

I see fluctuations in voltage sometimes with a tester. The voltage usually rests around 12.6 to 12.8 on a tester, so I know the alternator is working still. At least some. Also I see CONTROL MODULE VOLTAGE in the Hptuners scanner as 13.5V to 13.2V Most of the time
hptunerlog9-18-17.jpg


And I've never heard of an alternator "sort of dying"? It makes me think the problem is TRULY with the L-terminal wire, or the wire that turns "on" the alternator. I think it might just be not fully turning on. Or that part could be going bad. It is an original 1998 alternator from an LS1.

So here is how mine is wired. I made this schematic a while back for the swap
alternatorfinal.jpg

I put the brown wire into pin B. My next idea before replacing the alternator is to remove the computer control and try a typical 500ohm lightbulb lamp (is that right? iirc) to 12v and see if it will put out 13.5 or so on my meter full time instead of the 12.6 to 12.8 it does now. Is there alternatively anything I can do or my have accidentally done in Hptuners to affect this issue...

If anybody has any other comment suggestion (besides change the 25 year old alternator lol) I would love to hear it. otherwise this is simply an diagnostic events thread for records.

Update: 10-6-2019
sometime last month I finally realized that I have removed and never replaced the engine -> chassis ground cable.
Somehow the engine has been starting, charging, and running.... fine... I guess. All this time (maybe 1.5 years?!) without the cable attached.
Then I swapped the cam. And I think the extra spring pressure, just pushed it over the edge. The engine would no longer turn over anymore, even with a very strong battery.
The day after that happened I realized the cable was missing and... its been @*&@#*&$ing fantastic ever since, the motor cranks like it was hit by a bolt of lightning now.

[Mangonesailor]

Even though you said you don't want to hear it:

Recharging a dead battery on just an alternator can kill and alternator. I'd have a couple of parts stores test it.

[B52bombardier1]

Get your battery "load tested". This will be a much better test than simply checking the battery voltage. My engine at idle makes 14.2 volts DC at the battery so your alternator / regulator is quite low.

Rick

[kingtal0n]

Even though you said you don't want to hear it:

Recharging a dead battery on just an alternator can kill and alternator. I'd have a couple of parts stores test it.

I think this is a myth actually, I used to think this as well but over the years many engineers have commented that there really isn't anything inside an alternator to 'wear out' besides the bearing support system.

Get your battery "load tested". This will be a much better test than simply checking the battery voltage. My engine at idle makes 14.2 volts DC at the battery so your alternator / regulator is quite low.

Thanks, unfortunately I just put another brand new battery in tonight. I think my old battery tested fine but I insisted on a new one because I have no way to charge it. As you say it seems there is an issue, the question is whether the alternator itself is bad or if the control side of things is wired wrong. Maybe I forgot to put a resistor in the signal wire or something? I think I will try a 250ohm or 400ohm resistor in the single signal trigger wire?

[castorjames]

i recetly noted that on my 1st gen LS swapped truck, stays at 13-13.2 V,, looks like it needs 2 wires, one ignition and the other is 12v with the ressistor, im about to try it tomorrow and ill let you know..

take a look
https://ls1tech.com/forums/conversio...or-wiring.html

[kingtal0n]

theres def something strange going on here. I too will need to experiment with the 12v and resistors involved and get back to you guys about this because NUFF is ENUFF! lol

[doctorbigblock]

Alternators are not bullet proof.

There is a spinning rotor which is computer controlled on this series, and a stator which takes the magnetic field generated by the rotor and creates the 3 phase ac output which gets rectified by the rectifiers and sent to the battery. the rotor gets its variable control from a psudo regulator which as noted earlier is controlled by pulse from the ecm. Since the rotor spins it has slip rings and brushes to maintain the electrical connections as it spins. it spins on two bearings.

Slip rings and brushes wear out.
Bearings fail.
Rectifiers can short and become leaky.
internal regulators can fail.
stators can overheat and fail.

Bottom line CHECK the alternator.

I would be very careful about putting a fixed resistor into the control circuit of these alternators as you could cause damage to either ecm or internal controller if pushed to hard.

hope this helps.

[mymonte666]

I would go ahead and remove the alternator and get it tested, but be carefull with the testing. I had an 02 duramax that the alternator was showing weird readings, like sometimes it wouldn't charge my batteries and sometimes it would take it up to a minute to come online. Did some pocking around and found some corrotion on my + terminals. These gm terminals are terrible for corrosion. While i was at it took the alt to the parts store to get it testes. It checked ok.
I put it back on with fully charged batteries.
Few days after im sitting in traffic at night and and noticed my stereo volume had gone up. At the same time all my lights became way brighter. When i glanced at the dash, my volts were pegged out past 19v. Then a puff of smoke and the truck shut off.
The voltage regulator had failed and the aftermath was my 2 batteries (optima red tops)litteraly exploded shooting acid everywhere. About 75% percent of my fuses were burned and the inline fusible cable) the black one comming from the alt was burned.
Put a new alt and batteries on there and was gtg.

[kingtal0n]

WOW guys thanks for the awesome responses. Extremely detailed breakdown of alternator insides is VERY appreciated, I will save that for the future reference! My (our) question would be (was), are there any parts in the alternator in particular which could be worn excessively by having to re-charge a battery? This is what I was told was negligible, charging a dead battery doesn't hurt an alternator anymore than charging a live one. Running the engine without a battery for example, what sort of additional wear and tear would the alternator experience? My assertion was that there would be no additional wear, thus the existence of the myth that it would which is still a question on the table.


The Incident with the high voltage is definetely a wake up call of what is possible! I try to be careful, I have 200Amp fuse between starter hot 12v and the battery for example. I wonder if that would prevent a fire? Or what else I can do to prevent one?


In any case. I went outside just now and pulled my alternator plug off.
I cleaned the contacts with some brake cleaner (prolly not a great idea but eh)
Then I noticed the plug wire has 2 wires in it. Of course only 1 was connected. However, I must have seen this coming, because I found a little piece of white tape on the harness, which usually means I left a wire there un-plugged. So Sure enough, I took my white tape off and found the 2nd wire was simply disconnected. I must have read that only 1 wire was necessary and left the other one free in case I needed it later.

Well, it took me all of 5 minutes to re-connect and heat shrink that 1 other wire, making both of them complete. I really have no idea where that second wire goes, didn't check the schematic just assumed I had this planned a year ago as a contingency and crossed my fingers. Fired up the engine and sure enough- 13.89V on the meter immediately.

I checked my mystery wire (Pin C: generator duty signal?) just to see what it was carrying and it turns out to hold about 7.77v on the running engine! LOL.
No clue where it goes... it must run to the pcm through some kind of variable resistor that the computer controls? anyways it seems to work for the moment I'm excited to see if the car drives different, being that it isn't uncommon to hear how a car "perks up" with an extra 1-2 volts sometimes. I've been driving it like that with 12.8v for over a year! I thought the starter was going bad, because everytime I came to the car it would just barely turn over. I had a spare starter sitting in the car for a while but the original just never seemed to die. Huh! The freakin alternator must have been maintaining the battery at a ultra low charge! I am going to try disconnecting the battery again and make sure the engine stays running, just to put the nail in this coffin.

Last I should i mention the alternator in my swap is actually not easy to get to. There is a turbo crossover tube that comes kind of close to it, I would probably need to remove that.
I should have thought about this when making that crossover, but I figured it was all V-bands it wouldn't be that big of a deal if I had to anyways, I keep them clamps anti-seized up and pretty loose so they will fly right off. Still, not something I'd do just to check an alternator when something was clearly wrong with the wiring I was able to fix, luckily, THIS TIME. Ahaha vehicles

4:40pm I just looked in the wiring schematic and found this:
Red Connector:
Pin 52 GRY Generator Field Duty Cycle Signal

I bet that is the wire that I just added to the alternator. I didn't check (too lazy, might not ever check) but it has to be that one right?!

[kingtal0n]

The plot thickens.

I drove it today 30minutes~ and watched as the voltage dropped back to around 13.0v

I reasoned maybe the battery was topped off.

but then I parked for 20 minutes and started the car to see the same 12.8v on the meter.

I think the heat has something to do with it. Will re-evaluate tomorrow when its cold and try some more tests.

Ultimately it looks like I may need to either move, or move and replace the alteran... altrenan... altrernantor. aler oh forget it

[cobaltssoverbooster]

i could not for the life of me figure out our what was going on with my wideband readings. one day i decided to try something stupid and perform a free test to check loaded alternator condition. all i did was disable the injector voltage offsets from 11-max volt.
this caused my wideband to damn near stop swinging and made it super easy to tune. i took the alternator off and shelved it for rebuilding as a spare for my dragster. In its place i installed a powermaster alternator and upgraded the alternator feed wire and ground wires from the heads.
i would take some tools with you to remove the belt and alternator and head to a parts store like oreilly's that can test the battery stationary and loaded. They should also have a bench test rig for alternators (my local oreilly's has both which is why i brought it up). Since you brought your tools pull the current and have it tested. if its bad you already have the tools and core in hand so you can put the new one in.

[kingtal0n]

Well I wish it was that easy. To get my alternator off though I probably need to pull my radiator, and exhaust crossover. Probably take me 30-45minutes to get in there. I don't want to do all that without having a brand new alternator waiting to go on so I will do a bit more testing first to ensure I won't just put on a new alternator and have the same exact issue. And if I do buy an new alternator I'd like to get a brand new or refurbished AC delco unit (I noticed they are the same price? Weird right?), not some auto-store junk.

My plan for now:
1. First find out where that second wire goes.
2. see what the voltage is in that wire with and without it connected.
3. Then find out what happens if I remove the computer control and run a charge lamp in that wire instead.
4. Next see what happens to voltage when I disconnect and re-connect each wire in turn

I'd like to build a little list of confirmed behaviors. My installation is unique. There is a very long alternator wire running to the rear of the car, through a fuse box, then to the other side of the car to the battery. It may be that the alternator is simply unaware of a voltage drop. I notice that the ECU shows 13.2-13.5volts where the actual voltage in the car is 12.8 usually. This makes me think the computer is "under-commanding" the alternator load, which might have something to do with how my system is installed. maybe the computer is getting a better voltage being that it runs off the 0-gauge battery cable that feeds the starter, whereas the alternator sends its voltage back to the battery from the other side of the car. Actually now that I think about it, the constant 12v supply for the computer is coming off the 0-gauge starter cable, but the switched +12v for the computer comes from the chassis, which gets its power from the fuse box which is in the trunk. So I don't know which "control voltage" HPtuners scanner is reading from, inside the ECU, I must assume the constant side of things. So it would be an interesting experiment to change the +12 constant supply over the chassis harness temporarily to see if the control voltage reading in the scanner drops.

Not quite sure how to deal with this one yet. But it might be something like... running a 12v wire from the back of the car by the battery to the L-terminal through a charge indicator... I would try that before a new alternator.

[jsf55]

Alty wires are easier to wire separate, grey to exciter feed wire, rewire brown wire toexisting warning lamp, which needs ign live feed. Not controlled by PCM
I made this note when i wired mine hope it helps, I've had no charging issues. john

[kingtal0n]

see that grey one is messing me up. What is an exciter feed wire, the factory schematic for the LS1 98-02 alternator does not use this wire and that is the alternator I have. Yet, both of my wires go into the PCM because apparently the truck alternator does use this second wire. My alternator is currently controlled by PCM. And its only supposed to take 1 wire. lol

my theory right now is that the grey wire coming out of my ecu is providing 7.77volts for the truck alternator which I do not have. So it does nothing.
And the LS1 side of things is working, but poorly, either because the alternator is just 25 years old and failing or the computer isn't commanding enough output. 13.8v at startup tells me at least something is turning it on at first. The fact it dies without a battery (not a great test but eh) also seems to point to weak output of an aged failing alternator.

Also, I'll talk about it 6 hours a day for a couple weeks, discussing theories and procrastinating, and then it will take me like an hour to change when I'm in the mood -.-


theories.... yeah

[doctorbigblock]

There are more alternator configurations than you would imagine. As a work around for race cars there is a one wire alternator option which has an aftermarket regulator and provides its own excitation once the engine speed is brought up high enough for the residual magnetism in the rotor to start the build up process. Handy and functional but quirky. another earlier generation used the two pins with an internal regulator which used one wire to excite the rotor via a light to provide a dash light for a charge indication which went out when unit started charging. Or if you had a gauge used a resistance in the harness to replace the light. The other wire was used as an indication of battery charge level to tell the alternator how hard to charge. This system required no ecm and could be easily tested with test light or resistor.

The newer systems use only two wires. One to control charging and the large output wire to the battery.
The ecm already knows the battery charge level if all the proper wiring is in place. if this system has worked for over a year with out the other connection you don't need it and since your not sure where it goes to in the dash I would not hook it up. I know you don't want to hear it but alternators do go intermittent and from what you describe I would highly suspect it due to its age.

One thing you will want to be sure of is that you get the correct replacement. Or better yet if you have a good repair option at your location as I do, just have your original alt rebuilt with new parts which usually provides best results. Another test you can run and I am not sure if HP tuners software has the option. I know my Tech2 does is to take over the control line and very the command for charge rate to check internal status of alt. However if brushes and slip rings are worn very bad it's not a conclusive test. They can be intermittent before completely failing.

Ps
I know that I have not been specific about part numbers and pin numbers because you have to be sure of which unit you have. That is why I suggested a good repair shop if you can't be sure of its identification.

If swaps were easy everyone would do them. Good luck.

[jsf55]

The grey wire is just a 12v feed into it, mine was a truck alty 2003 suburban

[kingtal0n]

Some results are in!

I made a video to help show results hopefully it will work (sometimes windows movie maker causes them to freeze, if anybody knows why...)

If it freezes you can usually fast forward it through those spots


The 'yellow wire' (pic C which says GRAY but mine is YELLOW) does some weird stuff. It puts out voltage from the alternator that oscillates between 2.5 and 7~ volts while not running.

If pic C wire is cut, voltage appears to be coming from within the alternator, still oscillates, however seems to oscillate high as 8.16 volts instead. This also causes the brown wire oscillation to be raised to the same higher voltage.

On the running engine it changes from 7.65 to 8.7 when disconnected/connected.

The Pic C Yellow wire disconnected I see 13.6~ volts on the cold running engine so the alt appears to be "working without it"/

There are only 2 wires my alternator plug, but the plug might be from a truck and this is an LS1 alternator. So who knows (not me lol)

The external temperature of running engine alternator approaches 212*F~ when the voltage is dropping, and 212*F should be well within specification of the alternator?

Anyways. hopefully you just watch video and determine the alternator is WIRED normal, but the alt itself is BAD and needs to be replaced. Thats my best guess atm because it doesn't seem to want to charge a dead battery (the whole reason I noticed this problem to begin with was I had a batt die and wouldn't re-charge barely anything) which lines up with the drop in voltage on the warmed engine.

Im going to try couple more things. I will try apply 12v to the yellow wire with engine running then compare charge current with yellow wire connected/disconnected with 12v applied.
And finally if I can find a freaking indicator lamp (the one I was going to use turned out to be bad -.-) I will try brown wire to 12v through the indicator trick with and without the 12v applied to the pin C.

10 hours later:
Here is the latest result. I connected the brown wire to the charge lamp in the car, the factory bulb like it was wired for a factory KA engine. The voltage output appears to be the same but the charge lamp does not light. I confirmed the alternator is "working" by disconnecting the wire and seeing the running engine holds 11.x volts on the meter, compared to the 13.0v at the alternator. So I guess the alt is "good" just not good enough to really charge a battery back up. Ill swap the alternator then swap the battery one more time and start fresh in a couple weeks, thanks for all the support everyone

24 hours later:
Now that I've got the meter in the car all the time I can clearly see what is happening. When I flip on headlights and wipers in the rain especially the system drops to around 12.2v, and the normal battery charge level is 12.6-12.7v so I can see that the battery isn't even charging under these circumstances due to poor alternator output. What I find interesting is that the charge lamp still does not illuminate, the bulb is still off so the driver would never know the alternator wasn't fully charging.

I ordered an ACDELCO alternator from rockauto so I should have it changed soon enough, they ship pretty fast. I looked at it again on the engine and I think I might be able to change it easier than I thought.

[kingtal0n]

LMAO today I pulled the radiator and changed to the AC Delco alternator. It sure is pretty.

However- WHAM SAME ISSUE it gives me 12.2volts with headlights on driving at night.

@)#*()@($*&()$ LOL at changing out a perfectly good OEM alternator. My worst fear has been realized ;D rofl

only thing left is the wire coming off the back. I'll admit it isn't huge at first, and it should be 20 years old, so I am sure this will cure the issue when I change it.

I'm wondering- can't I just check the voltage coming out of the alternator at the back manually directly to verify it is putting out 14v and that my issue is a voltage drop?
What happens when I check the back and it tell me 12.2 or 12.5v after warming up? I get 13.8v on startup and it tapers off 13v 12.8 12.6 as if the battery is getting fully charged. The batt sits at 12.6v with engine off so it must be. It looks like everything is working fine, however, the voltage drops with headlights on to 12.2v sometimes 12.0 I think. And the system will not charge a dead battery i.e. if I run this batt down to dead, then jump start and drive the car around for 30 minutes, there is no charge in the battery after all that, it won't restart the car the next day. Although I did drive the next day with headlights on to walmart for a next battery and it restarted right there in the parking lot. So... not sure what is going on here just yet. Last thing is the engine won't stay running when I disconnect the alternator. As if the alt is just too weak, I feel that it wants to stay running for a split second then just dies as if somebody cut the ignition itself, it maybe losing its 'turn on' signal somehow through the oem wiring. I haven't tried this yet with the new alt but I feel the same result. The reason this is all so strange is the car is still wired like factory, I am using all the OEM fuses and wires for the charging/battery system connections. So the source for the charge lamp in the fuse box is the only wire 'turning on' the alternator, and it's source is the OEM solution, its not like I wired in a custom bulb or resistor or something.

[Mangonesailor]

What's your output amps of your alternator? Can you post some data of your idle/2krpm charging output voltages and amps with and without loads? Wh

If you need to get a meter the craftsman clamp-on multimeter is accurate... the one that measures DC and AC amps.

Before you question it's accuracy, we have several fluke meters and a japanese-made clamp meter that we use at work to measure current draw on various 3ph motors and DC bus-powered Lenze drives. I brought my craftsman in to work and compared all of the flukes and the Kyoritsu meter. The little craftsman measured the same as all of them within .02 amps. So I'd trust it.

My own 454 has an ad244 that I put on there, and I added a much larger, separate, charging wire to the battery and upgraded the ground. I put out about 20amps at idle with 14.4v at start-up, but that dies down to 13.x after the engine has ran for a specific period of time as commanded by the ECM (o411).

Also, how's your grounds on the car? Have you poked around and taken any readings?

You mentioned that you have a sensing wire terminal (I can't read through all your posts). You could very well connect it way downstream of the alternator and put it in the fuse block to ensure its putting out what it needs to (hell, if you really feel froggy you can put a pot in series and force the alternator to pump out everything it's got all the time.... which can also fry your alternator if you turn it up too high). I run with no remote sensing and my Optima
yellow-top charges just fine.

[kingtal0n]

I don't have any data or any fancy meters. I can't measure amps. The alternator is for an original 5.7L 2000 LS1, I think 120-130Amps.

HPtuners does report the voltage over time. I starts at 13.8v and drops to 12.8-12.6 after 10~ minutes from a cold start. Then if I flip on headlights it will be 12.2v~


For grounds I have a couple big wires in the trunk by the battery. I've tried adding temporary grounds all over the place, one from the batt to ECU, the engine to chassis, various supports but I think the battery is grounded really well. The single charge-sense wire coming from the OEM fuse box and runs the entire length of the car to the alternator right now. I get the same result using the ECU to charge sense wire.