Bill,

Yes, earlier (in post #13) the readings at the battery and alternator both read 12.67V. I double checked today after replacing everything and they match exactly again now at 12.70V.

My new ignition switch arrived earlier than expected from Gene, so I installed that last night. Here is what the one looked like that I removed...






The above photos are the original factory installed ignition switch after almost 8 years, 37,000 in-town DD miles.

After replacing this switch I had a noticeable increase in overall smoothness in the way the car idled and accelerated - somehow it also seems to have more power?

I did the Idle Relearn again today and it has been running great all day today so far.

The Voltage still dips on both dash meters when I come to a stop, but if the car had no meters, I would say it is operating at peak efficiency.
Today, the voltage was usually 12.9 - 13.0 driving at 45-60 mph dipping to 12.1-12.4 when coming to a full stop and then quickly recovering to about 12.9 - so I guess this is normal?

Thanks Bill for suggesting the Ignition Switch... looks like that was a big piece (if not the whole piece) of my puzzle!

 

No PROBLEM! Happy motoring!

BC

 

mine always reads low like that also. I even put a new alternator on and it was the same. I finally checked it with a multimeter and it's really charging at 14v. My gauge and on the DIC both read low.

 

WOOHOO!! add to your mod list!!

 

Hi,
I don't know if this is possible, but if you brought the car pre-owned, could you maybe have an under-drive pulley on it they forgot to tell you about? Just a thought.

 

Nope, bought it new in 2000.

 

Bill,

I just posted this in response to another thread, but do these numbers look right to you?

In the past two weeks I have:

• Checked/Cleaned Reconnected ALL my grounds (all of them looked good to begin with).
• Installed new Optima Red Top
• Installed new GM Alternator (under warranty)
• Installed new Ignition Switch
• Cleaned/Tightened Starter Pos Post nut

Car seems to be running fine now but here is what I show...

On Digital Multimeter Engine OFF:
at Battery 12.90V
at Alternator 12.90V

On Digital Multimeter Engine idling in neutral at operating temp:
at Battery 13.95V
at Alternator 14.12V

On DIC Engine Running idling in neutral at operating temp:
13.1 - 13.4V

Here is a pic of the Alternator they installed...
http://forums.corvetteforum.com/show....php?t=2089794

 

One more thing...

Last night, I finally got around to checking the Starter Post circled in red below. I was able to easily turn the nut at least half a turn (without the post moving), so I took the nut completely off, cleaned all the connectors, reassembled and reinstalled nut. I know the book calls for a torque value of 71 in-lbs on this nut, but there was no way to get any of my torque wrenches into that tight space (even my 1/4" Snap-On electronic) - so all I could do was tighten the nut by hand using an open end wrench. I noticed on my last small amount of pressure that the post started to turn as well (maybe 2-degrees) so I stopped tightening.

So have I ruined my starter because the post starter to move?

 

Today the voltage started reading really low again?

11.7 - 12.1 while stopped and a high of 13.0 while driving on the highway (based on the dash readouts)

Came home tonight and at idle in park the gauges showed 13.0
Voltage at battery with multimeter 13.57
Voltage at alternator with multimeter 13.76

So what do I believe?

 

The reading at the BATTERY and the alternator is all that matters. The battery is getting the correct voltage and (correct me if Im wrong) hasnt given you any issues.

If I were you, I would disconnect the battery, take a resistance reading from:

The alternator field terminal to the POS battery cable connector
The alternator to ground
The alternator case to the negative battery cable connector.
Engine Block to the negative battery cable connector

Post the results of the readings.

Your dropping voltage somewhere, we just need to find out where.

There is also a B+ connector on the Under Hood Fuse center. The feed comes from the POS battery terminal and from that terminal a wire feeds the passengers foot well fuse box.




Compare the VOLTAGE readings from ground to the B+ connector and the 12 VDC supply wire at the Pass Foot Well Fuse box.

BC

 

Bill,

I will take some readings tonight.

You are correct in that the car "seems" to be operating fine.

One other thing, the voltage readings at both the alternator AND battery are identical (12.9V) with the engine turned off - the discrepancy is only with the engine running (if that helps).

 

OMG So if you put EXPERT in the title you get 3000 replies and if not you get a "do a search" makes since...

Check your plugs..one is slighly loose

 

Bill,

Here are the readings from tonight...

Engine Turned Off:
Battery 12.45V
B+ Terminal 12.45V
Alternator 12.43V
Fusebox inside passenger footwell 12.42V

Engine Running in Park A/C Off:
Battery 13.72V
B+ Terminal 13.71V
Alternator 13.92V
Fusebox inside passenger footwell 13.71V

Resistance Measurements (Battery Disconnected):
Alternator to POS Battery Cable Connector 3mV
Alternator to Ground 361mV
Alternator Case to NEG Battery Cable Connector 3mV
Engine Block to NEG Battery Cable Connector 3mV

Just the one reading in bold looked strange to me, but maybe that is the way it is supposed to be?

 

You're showing voltage measurements where BC asked for resistance measurements. Resistance is in Ohms. Funny thing though, I was going to chime in and mention that it is good to measure voltage drops between ground points as this will indicate deficiencies in circuits while they're operating. 361mV is only 1/3 volt. In a vehicle, absolute ground is the alternators' chassis. Any significant voltage drops between the alternators chassis and any grounding point will reflect a problem. So far, I don't see any significant voltage drops. Need to keep digging.

 

I was scrolling to the end to tell you about the starter post when I saw you post about the tightening causing the post to turn. A friend had the same symptoms as you have with a Z06. The dealer replace the alternator and battery. Same thing. Sometimes it wouldn't turn over. I wiggled the battery cable and it started. When I turned the starter nut (red wire) it turned with my hand. As I used a wrench to tighten, the post turned and make a crackly noise. We took it back to the dealer, they took the starter off and the post was blackened inside and the bakelite insulation was charcoaled. A new starter fixed his problem.
On my 03, the voltage always reads within a couple of tenths of a volt on the DIC of 14 volts. At start up 14.3 and then after running a while, 13.9. It doesn't vary at all unless I turn on the lights or tap the brake, then it dips slightly and immediately back to 13.9.
I think you need a new starter, the post shouldn't turn. If you can't torque it down, it will build up heat and continue to get worse.

 

Sorry, I am still new to this electrical thing. The new $100 digital multimeter I got a few months ago still has some settings that I have to figure out - it was set to Ohms, but the readout was in mV? Anyway, this is what I got today measuring Ohms (and reading in Ohms)

Resistance Measurements (Battery Disconnected):
Alternator to POS Battery Cable Connector 0-Ohms
Alternator to Ground 2.7-Ohms
Alternator Case to NEG Battery Cable Connector 0-Ohms
Engine Block to NEG Battery Cable Connector 0-Ohms

 

I agree!!! Good recommendation!!! That connection needs to be perfect!
A NEW solenoid can be purchased from a reputable starter alternator repair shop for about $35-40 bucks and its easily replaced. I had intermittent NO START issues and replaced mine. FIXED! I had to purchase a very small deep well socket to remove the 3 small recessed screws that secure the solenoid to the starter.

I had some resistance between my alternator to ground also (4 ohms).

I added a 12 Ga stranded wire from the alternator case to ground G-101.

You can see the eyelet connected to G-101 in this pic.



In this pic you can just see the bolt for the case that I used to attach the other ground eyelet to:





Now I have ZERO RESISTANCE! Just purchase some eyelets and wire from Walmart and solder the eyelets on the short piece of wire and secure the alternator eyelet to one of the bolts that hold the case halves together!

 

Thanks Bill,

I will add the ground wire and see if that helps.

Regarding the starter, I spoke with a couple parts people at O-Reillys and said that it is not uncommon for the post to "slightly" move like mine did when tightening. They showed me how they are put together
and it is easy to see why. Of course, if you could turn it maybe a quarter turn it would be toast. They wanted to sell me a new started, but both agreed that I probably did not have a problem there? I also have not experienced any start issues at any time (yet).

I am a little confused as to why an auxiliary ground wire would help? Isn't the alternator case grounded to the block with the mounting bolts? Is that the ground we are suspecting is not solid?

 

Bill,

I just added the 12 Ga wire. I used the same Alternator case bolt that you did. Do we know what the torque value is for those bolts? It "feels" like it would be easy to strip the threads, but I also want to make sure they are tight enough.

Checked Alt to Ground Ohms and it is now zero as well.

Gauges in car still read low tonight and still dip to 11.9V-12.2V when coming to a stop and then come back up to 13.1V. Tonight it is sitting solid at 13.1 as long as the car is in motion.

I think I may have two problems (maybe related)?
(1) The DIC Voltage readout and the analog gauge seem to agree and both are incorrectly low by the same amount all the time.
(2) The voltage appears to dip by about 1V or so when stopped at stop signs and red lights - sometimes recovers while still stopped, sometimes not, but always comes back up (to 13.1V tonight) when accelerator pressed.

Problem (1) - It has been mentioned that a Tech II can re-calibrate the dash gauges to the correct values? Is that maybe what is wrong?
Problem (2) - I am beginning to wonder if maybe the serpentine belt or tensioner may be causing problems at idle? I am guessing that would maybe cause the alternator output to fluctuate? I am not getting any sounds from the pulleys and I replaced both belts about a year ago (3,000 miles ago) to be on the safe side.

I keep reading posts of people who get dash readings of 14V+ (and I used to), but I have not seen anything above 13.8V since I started replacing everything a few weeks ago.

 

I give up. I tried. That connection to the starter has to be torqued. If the post turns, it's loose inside. Keep on looking at other things and then post what finally fixes your voltage fluctuations.