I have an issue with my charging system:

The battery warning light comes on and sometimes stays on although i show 13.50 - 13.85 V. I have a voltmeter hooked up in the cab.

Searched this forum and got a pretty good idea of whats going on, but still have a question, but at least I found an answer to why, for the first few minutes after starting, my alternator doesn't provide a charge at all (glow plug circuit).

But I can't find why the battery light comes on even though my voltage is in the OK range.

Here are the specs:

• 2003 F250 6.0 Diesel
• 149k miles
• Batteries less than 8 months old
• Replaced alternator 1 year ago with Autozone reman unit (I wish I had research that before doing that. Now I would buy a new Ford unit.)
• Replaced serpentine belt and tensioner assembly 3 weeks ago.
• Replaced alternator 1 week ago because of complete failure (Autozone life time warranty exchange)

After the most recent replacement the battery light would come on. That's when I installed the volt meter to monitor charging voltage. But it is intermittent and I would like to find out if you think I am on the right track and learn how to test for it properly.
The indicator light doesn't typically come on in the morning (36 degrees), but comes on on my drive home (50-60 degrees).

I drive about 20 min twice a day (to and from work). Is this not enough to fully charge the batteries?

So, after reading what I could I narrowed it down to either a pigtail or a weak diode in the rectifier. I don't want to go and buy another alternator if I can avoid it, since I have the Autozone warranty.


Also, I read that a weak battery can destroy the FICM. Could some one provide a technical explanation why that's the case?

Thanks,

Patrick

 

Take it back to AZ. Unless you want to pony up for a diff. brand, You and AZ are tied together at the hip.

 

Alot on here would agree that DC Power Alternators are the way to go especialy if you have Big stereo or any extra electronics

The FORD reman alternators seem hit or miss on a good one

And with the 6.0 or probably any newer vehicle theres all kinds of electronics So its best to Have a Very Good and reliable charging system with Good Batterys A bad alternator or batterys will take out a FICM in a heartbeat. When your not producing clean good power it just makes the elctronics work harder to do there Job


Check them out if you can swing it these alternators are very well built
https://www.dcpowerinc.com/


I havent seen anybody have an issue with one of these DC Power alts yet

This is not an area you want to go cheap in either

 

the symtoms point to a bad alternator when there bad they usually have a hard time making power when they get hot

But have you cleaned all the connections and the 2 main grounds one by the A/C pump and the other by the Power Steering Pump

A bad ground will cause the alternator to run basicaly non stop then it gets way hot and wears it out quicker

One thing is for certain if that Battery light is on theres a Problem in the Battery/Charging system that light is Dead On the Money from my experiance

heres some other tests you can do with a DVM

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Fig 4 - Checking Ripple Voltage

Ripple voltage or (AC voltage) can be measured by switching your DMM to AC and connecting the black lead to a good ground and the red lead to the "BAT" terminal on the back of the alternator, (not at the battery). A good alternator should measure less than .5 VAC with the engine running. A higher reading indicates damaged alternator diodes.

Fig 5 - Alternator Leakage Current To check alternator diode leakage, connect the multimeter in series with the alternator output terminal when the car is not running. Leakage current should be a couple of milliamps at most; more often, it will be on the order of 0.5 milliamps. Use care when disconnecting the alternator output wire; make sure the battery is disconnected first
</TD></TR></TBODY></TABLE>

 

I would suggest double checking the plastic harness on the alt making sure all the wires are pushed in and making connection. Ask me why I say this, personal experience on this exact thing.

 

That's funny. The only things that are safe there are wiper blades and oil IMO

 

I use their brakes on my cars. Lifetime so every two or three years you get new ones free. It's time to flush the brake fluid at that time so you get two birds at the same time.

 

I have no luck with their rotors/drums ever. They always end up pulsating...

 

Auto-Zone, what a crock of KA-KA!

 

The oil and wiper blades are good! LOL

 

I have never had any luck with the "remans"
Check for a good reliable auto electric shop in your aria
Maybe have them bench test it
I second Blade's advise on checking ground connections including battery connections first
A bad ground seem to be the #1 killer of electrical components

 

+1 on the local shop repair/rebuild. They know you can just bring it back if there's a problem and they don't want to work on it twice. Local shop for me are a good bunch of guys and I like spending local when I can anyway.

 

Thanks all for your help. I wound up taking the alternator back to AZ. I installed the replacement unit and test drove for 20 min to make sure everything was warm. Seems to be good now.