Bobcatthewise

Hey. I have a 1994 z28 camaro 5.7l v8. My problem is I am having a low voltge charging issue with my battery. As long Im driving the car the battery charges fine, but as soon as I stop for a sign/light/etc... the voltage drops to the point where it is barely enough to keep the car running. Checked the voltage while the car is idiling and its only charging to 13.48 volts. I have just replaced my alternator, cleaned the ends/connections to the battery, and have a new battery. The problem still persists. As long as I do not put a load on the system the voltage stays good. Any thoughts?

Kevin Blown 95 TA

Is it 13.5V at the battery or alternator when the car is idling with accessories turned on? Or does it drop way down if have some stuff running? 13.5V isn't great, but the car isn't going to sputter and die from that. You turn the car off and the battery will eventually drop to 12.6V which is nominal for a charged 12V battery. So at 13.5V, it is still charging the battery and powering the stuff that runs the car like fuel pump, computer, ignition, sensors...

Do you have an aftermarket pulley set by any chance or is your car idling too low from a mechanical problem?

Bobcatthewise

When I have everything on I getting 12.4 volts and the small wire on the alternator is getting 10.5 volts. Orginal pulley set and no other mechanical problems. When the car goes up to 2500 rpm it stays the same.

90rocz

This is my son's car.
The battery doesn't go dead but it only measures 12.4v-12.7v with the headlights on, engine running 2000 rpm+...which should ask for max alt. output. The meter needle is in the top area of the red...13.5v no load....spec is 14.2v-15v
Autozone tested the in car output at 30 amps....passed all tests on the bench.
I'm a mechanic so I checked and cleaned all connections, voltage drop tests on all connections and large wires...good.

My Questions:
1)what voltage does everyone have on the small red wire first, Key On Engine Off?
2)Then, also with engine running everything hooked up?
3) If undersized pulleys, what are the stock diameters?

90rocz

Some background:
Recently bought the car, don't know if performance pulleys were installed but it had K&N CAI, Air Foil, Electric water pump, Lakewood LCA's, 2 performance chips.
I had to replace OPTI to get it running, then found out it had a knock that I was assured it didn't have. I pulled the engine and tore it apart and found the #1 rod was spun(.020"wear on crank and rod).
I totally rebuilt it, runs strong.
Harness was melted on the EVAP/AIR PUMP, so I repaired the harness but removed the AIR Injection set up, plugged the exhaust.

Guest47904

With KOEO the little wire going to the "L" terminal should be higher at around 12.6. Up that voltage with a temporary jumper wire to the battery. If the problem still occurs than it most deffinitely is an underdrive pulley issue. The equivalent of a low idling engine putting out less power from it's alternator.

Also be sure you have a sufficiently powered battery. Something like 700 CCA's.

sleeperLT1Z28

Is the alternator you put on a totally new piece or is it a Reman? I just swapped out my Duralast reman (since it crapped out) for a 'new' reman from Autozone. After installing it, the voltage would start around 14 at the battery and then slowly drop to 13 with no load. After much frustration, I decided to tear it apart. I found an old, original GM voltage regulator in there. After replacing it with a new one from BWD, I get 14.4 V at idle, irregardless of load. I'd say this might be your problem too.

90rocz

Thanks all,,,,been cold and put off troubleshooting til now.
I installed a good used and finally a reman. alternator.,,no change.

I get 14.4v cold and there is 12.6v on the "L" wire.@idle.
AS it heats up I get 13.2v @Bat. and 11.6v on the "L" wire.@idle.
If I rev it to 2,000 rpm it will come up to 14.0v
Fully warmed up I get 12.4v @Bat.and 10.9v on the "L" wire @idle.
Revving it to 2,000 brings it up to 13.0v max.
At which point the car begins to stumble, slow down and stall.@idle

Traced the "L" wire from the alternator past the PCM (not to)into the pass compartment to the dash. Almost "0" resistence.
Removed the IP
Resistors and diodes good, cant check the transistors and IC

Arrrrggh.

90rocz

Sleeper,,,,everything still good on your Z??
If so I will try replacing the Reg.

Bobcatthewise

Now has a brand new alternator and battery, and found out the old battery was bad. This has fixed most of the issue. Still has a gradual drop in voltage when let idle but slow.