Charging issues with the Burban...

[SRT41320]

So heres the Cliffs on whats going on...

1996 Chevy Suburban K2500 Diesel
does not charge above 14.0VDC (gauge on dash and batteries read the same) batteries look good and new alternator


The whole story...
The truck used to always show 14.2~14.6 volts on the dash. Last week it had a hard time starting, so i checked my gauges and noticed its was only charging about 13.7~14.0 volts. I checked the battery connections on both batteries and grounds in the engine bay, even cut the rubber off the terminals and replaced the botls and everything. No Change! Hooked up to a VAT40 (old school load tester / alternator tester) and noticed the max the alternator would put out was about 75~80 amps so it was weak but not toast. Also showed roughly a 30amp draw at idle (ac/radio/lights/etc were all on) was on Also had it tested at AdvanceAuto and they said it was good. I replaced replaced the alternator due to the fact that I knew from the previous test it was getting weak. No Change! Batteries look fairly new, and both hold a 12.7 volt charge after being disconnected. Also, when tested with a load tester they show over 1300CCA (they are rated at 700CCA each). So i do not THINK its the batteries. i've done a bunch of searching on this and cannot find anything except for that a lot of people have had similar problems, but nobody has posted the FIX.

Please help as this is getting annoying...

Click to read more...

 

[EmersonHart13]

Have you tried gmt400.com or fullsizechevy.com?

Do you have the big alternator?

 

[hellraiser319]

Sounds like you did most of the obvious, other things to check, grab a DMM, do voltage drop tests along various lengths of wire,, engine gnd to chassis gnd, chassis to - terminal, + terminal to alternator stud, alternator casing to - terminal (would show if corrosion b/w block and alt is an issue), shouldn't be more than say .2v with load, .5v tops. If you find a cable with a huge drop, there's the issue. Another thing, fusible link in the alternator line, but, you'd be getting nothing to the batteries and the gauge, as inaccurate the factory gauges are, still wouldn't show 14v.

Only other thing I can give ya, again, hoping your meter tests current, do a current draw test, key off, doors closed, disconnect - terminal, attach a jumper between - and cable, then attach meter to each as well, then remove jumper as long as the dome lights are off. This keeps the internal fuse from blowing. Do not open doors, do not turn on ignition, just let the truck sit. After it "settles down" after about a minute, shouldn't be reading more than 30-40mA tops or .03-.04A. If it stays high for longer than a minute or so, start pulling fuses. Rejump the connection, disable dome light, then remove the jumper, after it "settles down" again, start pulling fuses one by one until you see it drop. Circuit that makes it drop is the one in question. Could be anything from piece of equip gone bad, glovebox light switch broke, trunk ajar, etc.

 

[SRT41320]

its not the fusible link - i ohmed it out and it was fine - but i also replaced it with a solid 10ga wire just incase with no change. also i dont think there is a draw with the truck off - i can let it sit for a whole week and it will fire up, but i will try and verify that.

 

[Turbocharged400sbc]

is battery voltage jiv'n with the gauge?
hookup a good scantool that will give you the ign voltage at the pcm and compare to the DVOM at the battery and the gauge.

you can use some scanners with bidirectional controls to comand the alternator to full field and see what it can put out...keep in mind charging voltage changes with ambient temp. cold weather usually results in a higher charging voltage than hot weather as the batterys efficiency/resistance changes.

you will want to do voltage drop tests as the side terminal cables and battery cables in general are very good at hiding corrosion where you cant see it (inside crimped connections/insulation/etc.

 

[RICH17]

I was going to say the same as James. GM's seem to like to corrode inside cables. I would run new battery power and ground cables with some 4gauge and also some new ground wires. Made a difference on my Lumina and it has a police spec system with bigger wiring than normal

 

[Eagle]

I had to clean the terminals on that thing a bunch of times, but that would always fix it.

Have you pulled, inspected and cleaned each battery terminal?

 

[Turbocharged400sbc]

i kept doing that to jamies truck, always a low state of charge...even changed the starter...then said fuckit and cut the whole side post cable end boot off (the part that on earlier cables is molded to the assembly...newer vehicles you can remove the sheath by just removing the bolt and sliding the sheath off)

the battery cable was severly corroded where the copper was crimped to the terminal....and 4inches down from it

i cut off 3 inches and scrapped with a razor/sanded the wire and slapped on a universal side post repair.

fucker starts up like it was 1997 EVERY time now

 

[EmersonHart13]

I miss 1997...

OT: What temp does Jamies truck run at?

 

[Turbocharged400sbc]

the 454 sits at 200ish all day long loaded or unloaded creeps up a wee bit with the ac on

 

[EmersonHart13]

Mine sits at 210 all day long, i have read this is not unusual at all....crazy!

No AC, it does not work.

 

[Turbocharged400sbc]

no its not unusual...a motor should run at least 5* over Tstat temp any lower and the Tstat will cycle causing it to get hot/cool/hot/cool and cause wear and tear from thermal cycling.

also remember a hot engine burns cleaner and is more efficient in most cases....nowadays cars can hit over 220 and thats normal

 

[SRT41320]

is battery voltage jiv'n with the gauge?
hookup a good scantool that will give you the ign voltage at the pcm and compare to the DVOM at the battery and the gauge.

you can use some scanners with bidirectional controls to comand the alternator to full field and see what it can put out...keep in mind charging voltage changes with ambient temp. cold weather usually results in a higher charging voltage than hot weather as the batterys efficiency/resistance changes.

you will want to do voltage drop tests as the side terminal cables and battery cables in general are very good at hiding corrosion where you cant see it (inside crimped connections/insulation/etc.

I was going to say the same as James. GM's seem to like to corrode inside cables. I would run new battery power and ground cables with some 4gauge and also some new ground wires. Made a difference on my Lumina and it has a police spec system with bigger wiring than normal

I had to clean the terminals on that thing a bunch of times, but that would always fix it.

Have you pulled, inspected and cleaned each battery terminal?

ok, the battery voltage has been confirmed by a DVOM, Scan tool, and gauge to all be the same...13.8-13.9vdc

that being said, i did cut off all the rubber around the terminals and they looked ok, but as far as actually going further into the wires I have not. So either way i cleaned the hell out of them, installed new bolts for the terminals. Maybe I will do the "big3" upgrade and test the theory...

James, i did notice on my way to work the past couple mornings (when its been like 50-60*) it charges at the normal 14.4ish... is it possible that this is just temperature related? I know the theory behind the voltage/temperature change, but Ive never ran into this with another vehicle though...

 

[RICH17]

Temps will have an affect on the charging system and alternators have overheated before. I would definately do the "big3" just because GM wiring sucks. Also make sure you keep the area around the alternator clean and free of debris

 

[SRT41320]

its spotless + its a new alternator

 

[Stink Star]

It's incredibly rare, but the connector going to the alternator supplies voltage to regulate output... Sometimes this wire can get fucked (corroded, loose terminals) and that could affect output. Like I said its rare and a long shot but worth a look

 

[Turbocharged400sbc]

some have both a red and a grey wire at the alternator connector the red controlling the fiel strength (via pcm) and the grey i believe is a remote voltage sensing lead that not all cars have, the one's that have it typically seem to have alot of optional power accessories (luxury)