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Charging issue

B

bhiggs89

Veteran CEG'er
Joined
Dec 23, 2007
Messages
706
Location
Peoria, IL
Need some help diagnosing this.

2 days ago I was driving to work and the battery light came on. Luckily my mom's house is on the way to work, and she happens to have a nice big spare garage in the backyard. After pulling into the garage I grab my multimeter and test the voltage at the battery whole it was still running, I get ~11.9. So I'm thinking alternator, I had to replace it about 3 years ago with similar symptoms.

Fast forward to today, I replaced the old alternator with a new re-manufactured one from advanceautoparts. Go to start the car and the battery light is still on, the voltage at the batter is the same 11.9V. Now I'm a little mad, I take the old alternator to them and it tests good. I go back home and double check the connections at the alternator and they are ok. I check the mega fuse and it's ok. I have battery voltage at both sides of fuse. I've checked the wiring and I don't see any obvious signs of wear.

Where does the charge wire from the alternator go to?

Anything else I need to check?
 
I'd double check the wiring at the plug on the alternator..for a long while mine was wonky and would cause my system to not charge. Pushing the connector firmly into the alternator would cause mine to start charging again - eventually I just bought a replacement from eBay and spliced a new one on (my alternator ended up dying anyways).

As far as I am aware the 2/3 wire (not sure if SVTs use a 3 wire? my 99 2.0 uses 2 wires) runs closely behind where the alternator is into a large bundled connector piece - it clips into the plastic piece that the mega fuse sits ontop of and is on the passenger side - i'd make sure that connector is tight as well and no issues with the wiring there.

Beyond that - you may have wiring problems with the positive cables running in and out of the mega fuse - I know some people (myself included) just add an extra 4 gauge wire from the battery positive directly to the charge post on the alternator. The positive cables are a bit of a pain to get to (unless maybe if you have a professional lift or remove the intake header).

Also if you have an SVT I know some people mentioned cutting the sense wire and routing it to the B+ terminal on the alternator as well - there is forum posts here about that.
 
Check to see if the fog lamps work. If they are not turning on then the fuse needs to be replaced. This is also the fuse for the alternator voltage reference. And this is where the wiring mod comes in, cutting the reference wire from the harness and connecting directly to the B+ terminal on the alternator.
 
Fog lamps haven't worked in a few years due to an accident, just never got around to replacing the lamp assembly. So I assume that's not the issue.

On the 3 wire connecter I've got battery voltage on the red wire (12.1 V) , and less than battery voltage on the green/black wire (11.47 V) . Is that voltage difference normal? Or is that indicative of a bad green/black wire?

The wiring "mod" is to cut and splice together the red wire on the 3 wire connector with the bigger red wire coming from the mega fuse, correct?
 
bhiggs89 said:
The wiring "mod" is to cut and splice together the red wire on the 3 wire connector with the bigger red wire coming from the mega fuse, correct?
Click to expand...

The voltage sensing wire from the fuse box, which runs through the fog lamp fuse, is cut and then attached to the main B+ wire on the alternator.
 
If not done already, fully charge your battery, many try to use one severely run down and the alt will make no/little charge as the output is based on the field input going in from battery. Best way to shell a new alt there is, they overheat from trying to charge too much at one time.

Any battery under like 12.3 volts is an issue, you got no real power under that. I commonly found starting and running issues at 12.2 volts or lower on all sorts of cars when I was in parts. A good battery has and holds at 12.3 -12.8 volts.
 
Just replaced my alternator with a heavy duty unit..The last one replaced 6 yrs ago. My dash lights had started to flicker and even reving the engine didn't fix issue. Found the failing unit made the pos battery cable so hot the covering had started to melt a bit.With our Canadian dollar worth about half US dollar try not to look at the classifieds anymore lol
 
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