So as some of you may know I previously reported a voltage issue where the car would run for about 20 mins then it eventually stalls out if I don't keep revving the engine to bring the volts back up.

Well tonight I took the car to a shop and had them test the battery and alternator. The result was like this:
With the car shutoff the battery tested 12.65v
The car tested at 13.6 on the alternator with it running and nothing turned on - It passed every single time 10 times in a row.


Then we tested it with just the headlights turned on
It dropped from 13.6v immediately to 13.1v - It also failed the voltage reg test every single time we ran it with the headlights turned on. Could this be an electrical short in the headlight connectors themselves?
When I turned the headlights off and re-ran the test it passed again and again.

When I turned the lights off again it went right back up to 13.6 again.

Does this sound like its an alternator issue or could there be somethingelse that I am overlooking?

In my previous post I stated voltage being shown on the ipc/dic that fluctuated from 11.9 to 13.6 almost constantly. As I would rev the engine or drive with high rpms the voltage would increase from 12.2 back up to 13.5, but the voltage would drop if I was sitting idle or waiting at a traffic light. The voltage would drop really fast once the car had ran for 20+ minutes, but it would drop slower if the car wasn't running for long. The voltage would keep dropping until the car eventually just stalled out.

My buddy told me if the alternator can't keep charging the battery properly you will have close to 30 minutes before the car will die.
This seems like what is happening so my question is will I be fine running a 2001 z06 with a 110 amp alternator that only has led headlights?


Thanks

 

Take your car to Auto Zone and have them (for free) put your electrical system on their tester. You will know in minutes if your batter or alternator is defective.

 

I had a similar issue when I bought my c6. A copper wire in the alternator came loose and would touch inside the alternator. Caused the volts to drop as the car warmed. Had it fixed and no problems since. 80 dollars and i removed it and took it to the shop and then reinstalled it.

 

I had a LESS than 2 yr old Delco Pro battery crap out on me a couple of weeks ago. It wouldn't hold a charge....I'd charge it up, start the car, shut it down and the battery would be dead. As silly as this sounds, to prove out it was the battery and not the alternator I disconnected the positive lead on the battery while at engine idle. If the alternator / voltage regulator was bad the engine would shut down or run like crap until it shuts down. Give it a try. What do you got to lose ?

As for your comment " Then we tested it with just the headlights turned on
It dropped from 13.6v immediately to 13.1v - It also failed the voltage reg test every single time we ran it with the headlights turned on. Could this be an electrical short in the headlight connectors themselves?
When I turned the headlights off and re-ran the test it passed again and again.

When I turned the lights off again it went right back up to 13.6 again. "
I doubt it's a short , you are merely putting a load on the alternator and that's what causes the voltage drop.

You can also try putting more load on the alternator with the positive lead disconnected by putting on head lights, rear defroster, radio, etc, etc. If the engine dies it's time for a new alternator.

 

Two things, whatever you do, DO NOT:

• Turn-in your alternator as a core
• Disconnect the battery with the engine running

Keep your alternator, even if it seemingly fails tests. Plenty of horror stories here, and keeping it you can always have the options of rebuilding it or replacing the voltage regulator yourself.

​​​​​The alternator provides a 3-phase full-wave rectified output, as can be seen in the following graph (green trace):



The battery acts as a capacitor to "smooth" it out. When the battery is disconnected, the filtering effect is lost and the "wavy" output plus any surge or spike that may occur is passed to all circuits, which could result in damages.

Losing voltage when the load is increased and as temperature goes up might be an indication of a bad contact in the alternator-starter-battery chain. Check, clean and tighten connections at the starter solenoid.

It would be good if you provide a link to your previous thread as well.

 

The first thing I'd do is load test the battery...was that done ??
I'd also do a voltage drop test between battery positive and the "Bat" terminal of the alternator and between the negative post of the battery and the alternator case. Here is a video from Eric O, a sharp
diagnostic technician from South Main Auto...a Legend...this might help...like he said he checks for that 400 Hz frequency on the alternator control wire to see if the PCM is telling the alternator to turn on if you have a DVOM yours might have a frequency setting....GOOD LUCK !!

 

If you have a meter. Start it and turn on the headlights. Connect the meter leads with 1 lead on the battery positive post and the other lead on the alternator output stud. You should have <0.5V. If this fails, you likely have a bad connection at the solenoid.

The C5 alternator turn-on signal isn't 400Hz. It's simply 10V on the L terminal.

 

DO NOT disconnect the battery while car is running!

I would think measuring the voltage at the battery while car is running should be at least 14 volts, I usually get like 14.2 volts.
I concur with post 2, take it to AutoZone or Advance Auto Parts. They'll test the battery and alternator for free.
I concur also on post 6, if your alternator is bad, do not turn your alternator in as a core. Take it to an alternator repair shop and let them rebuild it.

 

Ok, why not , please explain.

 

GCG already answered that.
The alternator is not there to run the car's electronics, the alternators job is to charge the battery.