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Alternator Question

Old Sep 19, 2018 | 09:29 AM
  #21  
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Car started up this morning without issue. Do not have a volt meter but dash gauage was reading 13.9 for battery once vehicle is on. This means it cannot be the alternator correct? Wouldn’t it read around 12 if it was the alternator?
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Old Sep 19, 2018 | 09:34 AM
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Originally Posted by stilambo07
Car started up this morning without issue. Do not have a volt meter but dash gauage was reading 13.9 for battery once vehicle is on. This means it cannot be the alternator correct? Wouldn’t it read around 12 if it was the alternator?
Voltage reading on DIC is not true battery voltage at the battery !!!...circuit testing MUST be done at the battery...DVOM's are dirt CHEAP...get yourself one !!!
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Old Sep 19, 2018 | 09:38 AM
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Originally Posted by rwobs777
Voltage reading on DIC is not true battery voltage at the battery !!!...circuit testing MUST be done at the battery...DVOM's are dirt CHEAP...get yourself one !!!
This was the first thing done. Battery is good!
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Old Sep 19, 2018 | 09:45 AM
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Originally Posted by stilambo07


This was the first thing done. Battery is good!
When you get a DVOM !!....you can crank the engine without it starting by doing a "clear flood crank"...pedal to floor while cranking...engine won't start !!...less than 1/2 volt drop...and check alternator side also !!....MANY DIY’ers have problems understanding current flow on the negative side of circuits !!


Last edited by C5 Diag; Sep 19, 2018 at 09:58 AM.
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Old Sep 19, 2018 | 10:06 AM
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Originally Posted by stilambo07
Car started up this morning without issue. Do not have a volt meter but dash gauage was reading 13.9 for battery once vehicle is on. This means it cannot be the alternator correct? Wouldn’t it read around 12 if it was the alternator?
Correct, the alternator is charging correctly to show that much voltage on the display. Now, you need to dig further to find the issue. Either you have a bad battery that self discharges when sitting, there is an intermittent alternator connection issue causing it to quit charging at times so the battery ends up dead when you park it, or you have a drain in the car that kills the battery while the car is parked.

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Old Sep 19, 2018 | 11:19 AM
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Exactly what I feel it is. A drain somewhere. I know this car is notorious for that!

How do do you feel about starting here and seeing if it solves the issue!



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Old Sep 19, 2018 | 12:02 PM
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Originally Posted by stilambo07
Exactly what I feel it is. A drain somewhere. I know this car is notorious for that!

How do do you feel about starting here and seeing if it solves the issue!...
I suggest you get a multimeter so you can troubleshoot instead of "feel"

If indeed you have an abnormal battery drain, installing a battery switch is just a palliative, not a solution.

To check the drain, disconnect the cable from the (-) battery post and insert a multimeter set to read current in the 10A range. Connect the multimeter's negative lead to the (-) battery post and the multimeter's positive lead to the negative battery cable you just disconnected. Wait for the car to go into sleep mode and check the current. Normal reading should be around 25mA.

Here is a cut and past of a Bill Curlee writeup on C5 current drain issues. He suggests that between 15mA and 30mA (0.015A and 0.03A) is the correct expected draw:

The correct BCM current draw should be 30 Milliamps or less. Most C5 run around 25ma
but I have see some as low as 15 ma.

Leave the engine compartment fuse box for last and start with the passengers compartment box first. Pull the power seat breakers FIRST! The power seats have a tendancy stay on and cause this issue.

Also pull the fuses for the Bose system amps.

Examine the car in the dark for lights staying ON.

Once you prove the interior circuits good,,, check the headlight circuits, and then test the current draw of the alternator.

Look at my electrical stickey. I think I cover this in detail in that post.

There are several COMMON things that cause excessive current draw

- Seat multifunction switch & Lumbar Switch
- Bose Amps relay stuck on
- Alternator didoes bad and drawing current
- Headlight control module bad
- Interior light on (check in the dark)
- Added aftermarket accessory not shutting off

Last edited by GCG; Sep 19, 2018 at 01:18 PM.
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Old Sep 19, 2018 | 01:43 PM
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Thank you for all of the suggestions. Just got back from auto zone. Battery test is good. Turned car on and at battery read a little low. Went to alternator and connected positive and ground. Alternator was good. However, losing power going from alternator to battery. The power was much greater at the alternator than at the battery with vehicle on. This would be a connection, terminal, etc if I am not mistaken. Going to dig further.
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Old Sep 19, 2018 | 01:46 PM
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Have you made any modifications to the car? Stereo, amp, lights etc?
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Old Sep 19, 2018 | 01:50 PM
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Originally Posted by JR-01
Have you made any modifications to the car? Stereo, amp, lights etc?
Hid Conversion
Headunit
qtp cutouts
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Old Sep 19, 2018 | 02:02 PM
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Originally Posted by stilambo07
...Alternator was good. However, losing power going from alternator to battery. The power was much greater at the alternator than at the battery with vehicle on. This would be a connection, terminal, etc if I am not mistaken. Going to dig further.
Those are precisely a couple of things I suggested you to test, back in Post 12. I also told you how to proceed.

Last edited by GCG; Sep 19, 2018 at 02:05 PM.
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Old Sep 19, 2018 | 02:08 PM
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Originally Posted by stilambo07


Hid Conversion
Headunit
qtp cutouts
My last Corvette had an aftermarket amp installed by previous owner. That turned out to be the source of my battery drain.
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Old Sep 19, 2018 | 02:21 PM
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Originally Posted by GCG
Those are precisely a couple of things I suggested you to test, back in Post 12. I also told you how to proceed.
Yes. Thank you! Going to check those connections.
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Old Sep 19, 2018 | 03:52 PM
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Originally Posted by stilambo07
Thank you for all of the suggestions. Just got back from auto zone. Battery test is good. Turned car on and at battery read a little low. Went to alternator and connected positive and ground. Alternator was good. However, losing power going from alternator to battery. The power was much greater at the alternator than at the battery with vehicle on. This would be a connection, terminal, etc if I am not mistaken. Going to dig further.
It's most like the connections at the starter solenoid. Remove the big nut and the wires, clean the terminal ends up and re-install everything.
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Old Sep 19, 2018 | 04:32 PM
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Originally Posted by lionelhutz
It's most like the connections at the starter solenoid. Remove the big nut and the wires, clean the terminal ends up and re-install everything.
i cant find this^^^^ can anyone post a pic or deceive how to get to this solenoid.
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Old Sep 19, 2018 | 04:39 PM
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Follow the red and black cables from the battery going towards the engine. You pretty much have to get under the car to reach it.
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Old Sep 19, 2018 | 05:00 PM
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Originally Posted by stilambo07
i cant find this^^^^ can anyone post a pic or deceive how to get to this solenoid.
The starter solenoid is physically attached to the starter. As you can see in this picture, it is the cylinder-like device on its side, where the electrical connections are made:


This is a view from below, passenger's side:


This is another angle:


And another one:


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Old Sep 19, 2018 | 05:12 PM
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From the top I traced down and found this loose connector. But I’m the pic above it looks like it is disconnected as well. What is this and should this be hanging unconnected?

could I have found my issue?




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Old Sep 19, 2018 | 06:29 PM
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You need to jack up your car or put it on ramps, so you can work from below:


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Old Sep 19, 2018 | 06:57 PM
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Originally Posted by GCG
You need to jack up your car or put it on ramps, so you can work from below:

Wouldn't it be wise to disconnect the neg cable on the battery while working on this? I remember changing the starter on my C3 and I made some sparks when I didn't.
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