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04 Avy voltage flux, help needed

Aerohokie

SM 2020
PM 2017
Full Member
Joined
Apr 16, 2006
Messages
249
Location
Pensacola, FL
2004 Avalanche... When I bought it, I noticed the voltage gauge was hanging out solid at 13.5V but everything worked properly. I converted to electric fans with 05 fans, a painless wiring controller, new 145 amp alternator, and a new Red Top. I also sent the cluster off to get rebuilt with new stepper motors including trans temp.

When I got it all together I noticed the voltage would drop from 14.5 to 12 with fans activating and fluctuate between 12.5 and 14.5 under normal driving. I replaced the battery ground cable and cleaned all my grounds. Now it fluxuates between 14.5 and 13.5 with a noticeable flicker in exterior lights and interior lights. The flicker has been there since I did all the work.

I cut the fans out of the system and it still does it. If it's warmer than 60 degrees it never reaches 14.5, but the colder it is, the more stable the voltage is at 14.5. I also noticed that as it warms up and voltage drops, the temp gauge also drops below 210. My scanner shows no change in temp, but the needle is less. Voltage at 14.5=temp at 210, voltage <14.5 = temp <210.

So, my question is where does the voltage needle get its input from? What could explain the commonality of temp and voltage? Ground issue at the block? Any ideas would be most helpful! The other electric issues may not be related, but every now and again the unlock button on my remote won't work and then start again, but lock always works. Sometimes the driver side rear door won't unlock with the rest of the doors. I doubt they are related, but mentioning them anyway.

Future work is cutting all the ring terminals off the ground wires and installing new ones. If anyone can help me isolate this to a particular circuit or ground location I will be much appreciative!

Dave
 
Did you retro fit GM fans or go aftermarket.
 
Do you have the original alternator?

Sounds like you have a bad alternator or a bad wire connection somewhere.

What size alternator did you have before?

If you increased the size of your alternator you likely have to also increase the size of the wiring you used as well. I would suggest checking out the big three upgrade and doing that on your truck. Assuming that the alternator and battery are good this is likely the issue.

the data the cluster shows is read off the databus and not driven directly.

 
It had the 105A alternator to start. I added the 145 for the fan. Researching the 145A, I found that GM used the same cable from alternator to battery block in all of them. The alternator has been tested at Auto Zone 3 times. Twice in the car, once on the bench and on 2 different machines. Each time it's passed the test. I suppose I can put the 105A back in, manually shut off the fans and observe the flicker. I'm afraid it would kill the truck if the fans clicked on while driving.
 
You could try running a negative battery cable from the alternator mount down to the negitive battery cable on the lower engine.

See the picture 4 in that other post.
 
Ok, run from on of the bottom 2 alternator bolts to the main ground cable connection? I plan to hit all the grounds on the block this weekend and the G203, I believe, on the driver interior a pillar.
 
Doesn't matter if you have same cable sizes as was factory. You will still benefit from big three upgrade. No such thing as too big a wire... But too small, corroded or damaged and you will see what you are seeing.


 
redheadedrod said:
Doesn't matter if you have same cable sizes as was factory. You will still benefit from big three upgrade. No such thing as too big a wire... But too small, corroded or damaged and you will see what you are seeing.

I don't disagree with you. Too small should be a constant behavior though and wouldn't have been present in the stock set up. i did put a 4 gauge power wire I had left over from an old amp, but it didn't make any difference. The negative cable is new and the fan grounds to the battery post. The positive cable is possible. I haven't seen signs of corrosion in it yet. I plan on going over every single ground location this weekend with a wire brush and maybe even some solder.

The braided ground strap from firewall to block is corroded as all get out. I haven't been able to change it yet, so I moved the 4 ga from the alternator and put it from firewall to block. Another thing I want to do is remove the underhood fuse block and thoroughly clean it.

 
Do NOT solder the main battery cables... It will create a resistance in the wire. They should only be crimped or "welded" on. (GM Welds their wires that aren't crimped)

The ground strap you mention at the fire wall is the main one for the vehicle. Simple rusting of the strap is not a big deal but have to insure it is solidly connected to the bolts.

 
Aerohokie said:
I plan on going over every single ground location this weekend with a wire brush and maybe even some solder.

DO NOT solder them. That will make your fluctuation worse. Crimp, if you are not confident, or don't have a good crimper, they can be stick (arc) welded at the back of the crimp if you have aluminum stick and person that can do it properly. Soldering as Rod mentioned is only going to add resistance to the cable in a non-uniform manner

Adding a ground strap to the alternator itself is where I would start. (as MS03 mentioned)
I run a twin charging system and one side was showing fluctuation. Added a secondary cable from the alternator down to the frame rail where my ground for the first battery is on that side is and it disappeared. I think having separate ground locations for the alt (the bracket itself) and the battery was throwing the system for a loop.
 
Thanks for the solder info. I didn't want to do that anyway. To be fair, the ground strap at the firewall/block isn't rusty. It's blue/green corroded. I have the new one, I just have to get back there. When I do, I'll move the 4ga backup wire I have there now to the alternator bracket and see if that works.
 
If you have a new ground strap I would suggest leaving the old one on but put this new one on under it. Also use star washers between them. The surface corrosion won't affect the electricity but unless at the connections. Star washers put a bite into the surfaces and insure they conduct electricity better between them. Especially copper washers if you can find them.
 
Good to know. I tried valiantly, but I couldn't get to that darn bolt. Even with the flex wrench, I couldn't get a good angle. I wish I had addressed this when I had the intake off for the knock sensors. I also couldn't find the ground on the left front frame rail in the wheel well. The 2003 grounding locations showed it as a 4wd harness ground, but I didn't see it.

Ended up replacing my steering wheel buttons and doing the cabin air filter mod. I did ground the alternator though. It seems a little more stable, but still dropping down to 13.0v when the fans kick on.
 
The ground is on the outside of the frame by the body mount.
Right under the footwell.
 
Working on your grounds.
Are your fans stepped to come on in progression to high?
Do have dual fans that are stepped to come on?
You mentioned heat seems to have an affect, have you tried the
old alternator and bring it up to temp?
Something in new/rebuilt alternator with heat and under load?
One of the fans is bad drawing excess amperage?  
Bad fan controller, I have had good lock with PianLess support.

In the jeep days if I overloaded the alternator it would not recover
until I turned off some lights. Burned a few up even some costume
made for me. 

 

 
MS03 2500 said:
The ground is on the outside of the frame by the body mount.
Right under the footwell.

I know that ground. Using the 2003 ground locationn thread
http://chevyavalanchefanclub.com/cafcna/index.php/topic,103136.0.html

I am talking about location 6 on the transfer case harness routing graphic. It looks like the shock mount, but says its G110. The next graphic is under the driver door and says G110 also. Thus my confusion.
 
JVZL1 said:
Working on your grounds.
Are your fans stepped to come on in progression to high?
Do have dual fans that are stepped to come on?
You mentioned heat seems to have an affect, have you tried the
old alternator and bring it up to temp?
Something in new/rebuilt alternator with heat and under load?
One of the fans is bad drawing excess amperage?  
 
Fans come on at 50% and then step up in 10% increments to 100, at least they are supposed to. The logic does have an AC turn on which goes to 100% when the compressor engages. This is how I test it. Tomorrow I will change the alternator to the 105 OEM one. If I can get my multimeter on the fan line, I'll check their draw. If this doesn't work, I'll try to talk advanced into exchanging the alternator despite it passing their tests. I'll call painless too.
 
Today I put in the 105 alternator and the flicker went away. I went to advanced auto and the manager let me return it for a new one. The flicker is greatly reduced. It held 14.0 solid in warm up. 13.8 with fans on. 13.0 fully loaded at idle. This is from in cab odb2 scanner. Under the hood was about .5 higher. So I do have a voltage drop between charging circuit and the obd2. I guess back to checking grounds, calling Painless, and inspecting wires.
 
 One other thought my wife has 2004 PT Curser that came up with a flicker.
This was still under warranty. Chrysler knows of this. It?s one of those dose not
cost lives so too bad no help. The dealer had a rep out and they were even going
to the forums to see what people were doing.
To shorten this up they did all the ground up grades. Still there. I have a friend that
has his own shop use to work at this dealership. He contacted them for me they listen to him.
Found the computer was receiving full voltage but was not putting out full voltage.
Then they fried the new computer and had to put in another one.
Would someone of the guru's know where to check out puts?
Maybe not a concern?
 
Interesting. I am thinking of getting a black bear tune. Perhaps I'll see about getting a different core to send them. I would also like to get the wiring to have PCM controlled fans and ditch the controller altogether. The dual controller controls both, but not independently. So with ac on and fans on full, that's 50 amps at idle
 
Aerohokie said:
Today I put in the 105 alternator and the flicker went away. I went to advanced auto and the manager let me return it for a new one. The flicker is greatly reduced. It held 14.0 solid in warm up. 13.8 with fans on. 13.0 fully loaded at idle. This is from in cab odb2 scanner. Under the hood was about .5 higher. So I do have a voltage drop between charging circuit and the obd2. I guess back to checking grounds, calling Painless, and inspecting wires.

I don't think a 0.5 V drop is much to worry about.  100 amps through 0.005 ohms of resistance creates a 0.5 V drop.
 
Have you check into Nelson Performance for your tune and harness?
 
Another consideration since your 105 amp alternator is not causing flickering...

What brand is your alternator. I have heard of some high output alternators putting out an excessively "noisy" output. Could be just a cheap alternator not putting out consistent output? If you have a 1farad capacitor you could check this by putting it at the battery from your alternator line and see if it smooths out the flickering... Would really be telling if you could put a scope on the output and see what it is doing.

Rodney
 
JVZL1 said:
Have you check into Nelson Performance for your tune and harness?

I was going with blackbear because they will send me the harness to data log it then make the tune more personalized for my truck. Nelson was more one size fits all unless they offer that service now.
 
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