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Discussion Starter · #1 ·
Hello- I am new to this forum and looking for some help. Working on a 2004 Focus ZTS w/2.3 motor. Just started having charging issues last week.Battery seems good- holds charge for 2 days w/o issues. Based on initially diagnosis w/ multimeter we suspected the alternator. Replaced it with a rebuilt NAPA unit that failed to fix the issue. We then removed the alternator took it to Autozone fro testing - failed. Went back to Napa and got another that we bench tested-good. Put it in the car and still no charge at bettery(12.2 V).
We also have checked the three prong connector for issues. We get 12V on the red wire- also checked 1 amp fuse in box (#10) all OK. The gray wire from the PCM shows 9V with key on- I believe this is OK. The middle blue wire shows 0 V with key on- also OK?
Next tried to Ohm out main lead to the alternator form battery. Shows 30-60 Ohms. Not sure if we are just not getting a good contact with the tester lead. I have tried scratching the surface to get better contact - still nothing better than 30 Ohms.
Is there a fusible link on that line that could be the issue? Maybe a poor connection at starter end? I will try to bypass the cable with an additional lead from the battery tonight. or could there be an issue with the PCM?
Thanks in advance for your help.
 

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'Battery seems good- holds charge for 2 days w/o issues.'

It really kills me how many people dismiss the battery through one warped point of logic or another to simply tear the works up testing everything else under the sun.

That 'battery good' logic is some of the worst I've ever heard. Even bad batteries can do that.

LOADTEST THE BATTERY. An off battery can toast alternator after alternator.
 

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...tried to Ohm out main lead to the alternator form battery. Shows 30-60 Ohms. Not sure if we are just not getting a good contact with the tester lead. I have tried scratching the surface to get better contact - still nothing better than 30 Ohms.
Is there a fusible link on that line that could be the issue?
Definately check into that! The cable should only be a few milliohms...not ohms. Some Foci have the fusible link and others don't, but you will find any issues with it when you check the ohms again.

BTW: Welcome to FF.
 

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Look at the starter interface there, common to be trouble at it from melting. The plastic cracks and then water gets to the crimps up in there. While the ohms should be as close to zero as possible I do not look at 30-60 as much of a problem. There is a certain length of cable there and there will be small resistance from that. I have never gotten miiliohms on any one of those I've checked, but usually like 10 ohm or less. My happy place............

A battery at 12.2 volt is dead enough to cause troubles, these give trouble at 12.3 or less.
 

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^^^Hmmm....I would be horrified with 10 ohms.

Let's say the alternator was putting out 20 amps (a low amount) and the cable was 10 ohms...the voltage drop in the cable would be 200 volts.

The problem with measuring very low resistances is twofold. First, it requires a good meter to get an accurate measurement. Second, it requires very good connections...a bad connection can be more resistance than the resistance being measured.
 

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Discussion Starter · #6 ·
Seem to have figured this out. Took the battery in for a test- was fine. Cleaned terminals and reinstalled. I put a jumper between battery pos and large wire on alternator. Start motor and measure 14V at bettery. So looks like large wire has an issue.
Plan is to disconnect from the starter and clean contact and retest. If still an issue we may need to replace harness. Looks like we need to remove starter to get good access to harness.
 

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Another thought...

I wouldn't bother with replacing the OEM cable by tearing into the harness. Just cut the cable where it enters and exits the harness and abandon it. Have a new cable made up and ty-wrap it along the harness between the alternator and the starter. You could make the cable yourself or try an audio installation shop. You can also increase the size of the cable a little while you are at it.
 

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Discussion Starter · #9 ·
How tough to replace the cable. I think it is also part of the pos battery harness? We have starter out and hanging. Removed nut holding harness but can't figure out how to get plastic cover off. Seems to snap together but not sure if we need to remove the other connections first?
 

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Yes, it is part of the positive battery harness.

If you have determined with your meter that the cable from the starter to the alternator is bad, then you have nothing to lose by cutting it off. This would leave the battery to starter part of the cable. Then make a new cable to connect alt to starter...you can even go alt to battery positive if you want.
 

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Far easier to tap in a new line like that last post. The whole thing is kinda messy to change out.

'^^^Hmmm....I would be horrified with 10 ohms. Let's say the alternator was putting out 20 amps (a low amount) and the cable was 10 ohms...the voltage drop in the cable would be 200 volts.'

That's what the rules say but the car can't read. I've had and probably have that much resistance right now on mine and charges all day long. And not the first time, I've seen it on other cars. Yes, you probably need to dick around and get lower numbers but I don't bother if it's working fine. Gonna have trouble losing 200 volts with only 12 there to begin with...........I was most likely incorrect with the 30-60 ohm statement though. I'll say again I really don't worry about 10 but I would if issues showed up. I do not and never chase or use all the extra grounds most here do but I know to go there if I have an issue, it's just never been needed. I ran my own positive cable long ago on both cars when the OEM both melted. Flawless since then. Like I said, I haven't gotten milli-ohms on virtually anything I've read but the fix whatever it is goes up and stays up. Absolute zero is just not necessary unless using very low volt circuits. I even get like the up to 10 ohm readings on 5v sensors and no issues again. Maybe I'm not that good an electrician but it seems to work and even did on the computers I built as well. No troubles there either. All I care about is things working and longterm, the rules are great but often can be broken to good effect. I certainly seem to do it enough.

Now if OP thinks a problem there then the ball is in his park of course. One has to accept any ideas they get when they cannot work it out themselves. And of course not saying any ideas given here are bad, they are NOT.
 

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...Seems to snap together but not sure if we need to remove the other connections first?
On my car, that plastic housing does "snap together". Once un-snapped and opened, I was surprised to see how it connects; without any individual terminal lugs! -just a single cable and an in-line type of terminal. Very unique.

Picture explains it:
 

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Discussion Starter · #13 ·
Thinking about making my own harness as suggested above. What about fusible link? Is it needed? What gauge wire should I use? Also should I cut old one out?
 

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Many people make their own and go with larger cables. Search for big-3 upgrade. Use wire bigger than OEM for sure.

Fusible link is not even installed on many, so I would say it is optional anyway. I would go without it.
 

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I did as much research as I could to find the OEM battery cable wire gauge size. It looks like it is 6 gauge. So, 4 gauge would be the next logical bump up (remember that the number goes down as size goes up). If you have a high power audio system, then 2 gauge or even larger should be considered.

Using the chart here (http://www.powerstream.com/Wire_Size.htm) you can see that 6 gauge has about .3951 ohms/1000 ft of resistance and has a recommended maximum chassis wiring amperage of 101. Bump up to 4 gauge and it has about .2485 ohms/1000 ft of resistance and has a recommended maximum chassis wiring amperage of 135 (more than 30% increase).

BTW: There is about 6 feet of wire between the alternator and the battery, so the total ohms for a 6 gauge cable should be about 2.4 milliohms. Some additional resistance would be added by the lugs and the bolted connections.
 

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Discussion Starter · #16 ·
Just installed 4 ga cable between alt and battery. Used 51"length. Now just need to tidy everything up and secure it along the way. I think it is a robust solution. Many thanks to all who helped.
 

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Awesome!!!!!!!

Be sure to pay attention to the places where the cable comes into contact with items. There is a lot of rubbing going on under the hood with the engine vibration, so protect contact areas from damage. Some hose can be used if necessary to place between the cable and areas where the cable might rub.
 

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Watch specifically for rubbing after starter but before alt on back of motor. Fasten cable down, don't let it flop in the wind.
 

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I bypassed my battery to alternator with 2 ga over 5 yrs ago.
 
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