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Replaced Alternator and Batteries. Battery light on.

17K views 11 replies 6 participants last post by  kaya  
#1 · (Edited)
Just the other day my wife called and said there was white smoke coming from under the hood of the truck and she could smell something burning. I got the truck home and tried to start it and the batteries were dead. The smoke was coming from the passenger side which is were the alternator is. So I bought a 200 amp reman alternator from Advanced Auto (Carquest) and installed it. I could see that the original alternator was definitely burnt. I had put both batteries on charge before I started the replacement. Put them back in and tried to start the truck but they were still dead. Took them to Auto Zone and they both tested bad. I purchased two new batteries and the truck starts fine and no smoke or burning smell. But now the battery light is illuminated. With the engine off I tested both batteries with my multimeter and both are over 12V. Started the truck and the voltage goes to 13.5V. Revved engine to 2500RPM voltage holds at 13.5V. Turned everything on to put a load on it (lights, wipers, hazards, seat heaters, ac, etc) and voltage goes to 14.4V. So it appears that the alternator is doing its job. I've read on some other forum that not all alternators are recognizable by the computer? Anyone know if this is true? What else should I look for? Thanks guys.

2008 F250 119k miles
 
#4 ·
Stupid Question

This may be a stupid question, but do you have two Alternators? I had to replace one alternator, bearing was going and while I was in there replaced the second one. I had the Batt light come on at idel and it turned out one of the alternators was bad.
Just a thought.
 
#8 ·
Every week or so I top off my batteries using a good float charger. I like Battery Minder brand, puts out 8 amps but will de-sulfate the batteries and charge them to 100%. In the winter I do this every week. I have a connect wired to the truck and can connect it with the hood closed. Running the charger all weekend.

When I first purchased the truck used the charger worked for hours to get the batteries into shape. Now in a few hours it gets into the float charge mode.

The 2006 vintage truck would eat alternators due to weak batteries. Not as big of a problem with the 2008-10 vintage, but all diesel love to have strong batteries.
 
#11 ·
Yet another alternator thread where voltage is assumed to be the pass factor...

Amperage is totally different, and monitored by the 08+ trucks. My guess is that the new alt although putting out 14v is not putting the amps needed out to keep the charging system going. Seen this serval times with A/M alts and Ford remans. Get a high amp probe on it when running and see what it puts out. The computer has to see the amp load increase or the light will come on. Most of the dead alts on 6.0/6.4 that we see will put out 13v but 0 or very low amps.

I know this is shocking (ha pun intended) but voltage does NOT keep your battery's charged....amps do!!!