Drag Racing Tech - Not charging nough after battery relocate?




03 BUSA
09-03-2011, 08:41 PM
Any ideas of what to look for? The guage shows right at the 13 volt mark. Needs to be a little higher. Car starts pefrect every time just seems the alt is not putting out 100%. I have seen other use the escalade 200 amp altenator. Before going this route wanted to check in and ask.


Old Geezer
09-04-2011, 08:10 AM
Run the volt drop tests on the charging system. [Better yet, on the entire car]
I'd not rely on the "gauge"...A data log would be much more accurate.

Bluestreak
09-04-2011, 08:20 AM
Run the volt drop tests on the charging system. [Better yet, on the entire car]
+1

Anything over .5v on any one wire... clean up the connections, apply some dielectric paste, and recheck voltage drops. If you have an amp clamp, check your generator output, too.


dtroike
09-04-2011, 11:04 AM
There are a ton of threads on here with your same problem but no answers although a weak ground would be most likely. I have the same issue and all +/- wiring checks out good perfect .1 voltage drop from front to rear under load. I've done everything short of driving a grounding rod into the dirt. It charges perfect when I first start it up but drops lower than it should be after it runs for 15-20 minutes. I bought a 145 amp alternator out of an 03 tahoe off ebay and it definetly helped but it still drops down to about 13.1. I would rather it not ever get below 13.5.

03 BUSA
09-04-2011, 02:45 PM
Mine will charge 14.2 on a cold start and then after driving it will get as low as yours if I have everything on headlights radio ect. But just normal driving it will charge 13.60. Is this enough for all the computer stuff or should it be the 14.2 like it was with the battery up front?

bonnarls1
09-06-2011, 09:12 AM
Mine will charge 14.2 on a cold start and then after driving it will get as low as yours if I have everything on headlights radio ect. But just normal driving it will charge 13.60. Is this enough for all the computer stuff or should it be the 14.2 like it was with the battery up front?

mine does the same thing i'd like to know if thats ok to????

TurboStangJON
09-06-2011, 01:17 PM
Do you have the alternator wire ran from the alternator directly to the battery or did you splice in up front? If you spliced in up front using the factory stuff that might be part of the issue. Another issue is running the battery ground to the chassis. A lot of aftermarket wiring manufacturers recommend running a ground wire from the battery all the way to the front to the engine. Granted this is for optimal conditions an a lot of people get away with doing it another way. I think in your case 13 volts is normal for a charging system otherwise you would be having starting issues. I would just check the connections, drive the car, and if your not having any issues I wouldn't change anything.

03 BUSA
09-06-2011, 01:46 PM
Why does it start out normal 14.2 and drop to low 13's? All factory wiring is gone. This is a clean install with no splicing anywhere. Each location has it's own dedicated wiring.

BlackScreaminMachine
09-06-2011, 02:27 PM
Alternator could be on the way out.

slow67
09-06-2011, 02:58 PM
Why does it start out normal 14.2 and drop to low 13's? All factory wiring is gone. This is a clean install with no splicing anywhere. Each location has it's own dedicated wiring.


Is it still controlled by the PCM?

TurboStangJON
09-06-2011, 04:58 PM
Why does it start out normal 14.2 and drop to low 13's? All factory wiring is gone. This is a clean install with no splicing anywhere. Each location has it's own dedicated wiring.

I consider anything above 13.2V normal for a charging system. It would be nice to load the alternator a couple of times and check the amount of amps it's putting out. If the installation is correct then the only thing to blame would be the alternator. Like I said before I don't think you're having a problem considering it starts and runs fine. If it wasn't charging enough you would be having all sorts of issues.

03 BUSA
09-06-2011, 05:59 PM
Is it still controlled by the PCM?

Yes..

MUSTANGBRKR02
09-06-2011, 06:41 PM
I have noticed the same problem on mine and will be redoing everything in a few weeks in an attempt to fix this. I start out about 13.4 and drop into the 12's but have no starting issues or anything.

03 BUSA
09-06-2011, 07:32 PM
I just ordered the Escalade 145 amp altenator. Should have it in my hands tomorrow. I will post up results. I am starting to think the stocker isn't strong enough for all the extra wire. For $50 + $20 for the core it is worth a shot.

slow67
09-06-2011, 08:16 PM
Yes..

Then it is likely the PCM doing it. My car has the battery up front, and a stock alternator. It drops down into the mid 13s after several minutes (not exactly sure where, because of the stock gauge) and has done it since day 1. If you want to wire it up like a 98 f body, it doesn't use the PCM to command the alternator.

03 BUSA
09-07-2011, 07:24 PM
Installed the Escalade 145 amp and yet I haven't driven it yet just got it fired was charging 14.6 at idle. The only thing I did not like about the larger altenator is the feed wire/positive wire terminal on the 145 amp is for a 10mm nut while factory f body is a 13mm nut so the stud is alot thinner on the larger altenator. Other than that is was a straight up swap that so far seems to be what I needed. I will not get to drive it till saturday but I will post up the final results. $50 for the 04 altenator and $20 core charge I felt was worth a try.

sleeperLT1Z28
09-09-2011, 09:04 AM
Then it is likely the PCM doing it. My car has the battery up front, and a stock alternator. It drops down into the mid 13s after several minutes (not exactly sure where, because of the stock gauge) and has done it since day 1. If you want to wire it up like a 98 f body, it doesn't use the PCM to command the alternator.

So LT1 PCMs control the output voltage? My '93 alternator is a one-wire. I assume the PCM must vary the voltage on that wire? If I wanted to wire it like a '98, would I simply supply a 12V keyed source to that wire?

Fafonfoe
09-09-2011, 10:06 AM
Answer. The PCM controls how much charge the alt. will kick out. If your battery is charged completely and your at higher RPM it can drop to 12 volts easily. Its a system to keep from over charging the battery. Sounds dumb but ran into the same problem where I thought the alt. wasn't charging. I researched and talk to a friend of mine who designs parts for the new ford trucks and this was his answer. It makes sense. You can damage a battery by constantly charging it, you will see the volts changing depending on many variables. I hope this answers your questions. Don't get another alt.

Also I have three other GM vehicles that all do the same. Twp are brand new.
Good Luck.

dtroike
09-13-2011, 09:08 AM
Did you figure out if your problem is fixed now? Also where did you run the ground for your battery? I am using the same alternator and it charges about 14.5 when cold and then drops down to around 13.1 when warmed up. Ive even dried adding a resistor in the ecm wire to the alternator and bypassing the ecm all together and just using a resistor. Nothing made any improvment, and I have tried 2 stock alternators and now the 145 amp that is working the best. Its a very common problem with the battery locate but I havn't heard any for sure fixes for it yet. I dont remember for sure but I think before I moved the battery my voltage whould never drop below high 13's.