check your connections, could be a dead cell in the battery or an intermittent failing alt/voltage regulator.

 

Had the batteries tested recently and was told they check out fine. But they are NAPA batteries, so who knows. The one connection keeps corroding all to hell (drivers side positive terminal), otherwise things are normal. What is the alt/voltage regulator, and how can I check it?

 

alt = alternator. the voltage regulator is apart of the alternator. you can take it to a parts store and have it tested.

 

Have look for crappy ground connections . Batteries and main / ficm harness's . Fuzzy grounds will do remarkable things . Your just coming out of winter and this is when a lot of things start to corrode or build " films " .

 

I read somewhere recently that a corroding positive terminal means the alternator is failing to charge, while a corroding negative terminal means the alternator is over-charging.

I'll try to find a link. It made sense at the time.

 

I love it when people ignore obvious signs and always say "they tested fine"

 

Just passing on what I was told when I had them checked.

 

I hear ya... it happens all the time.

 

Any "obvious " conclusions on this ?

 

I will update when I get the alt tested and the batteries re-tested. In the meantime, does someone have a list of where all the grounds are?

 

Chits obviously broken.

 

I can help with the "big 3" info...

1) Alternator positive cable that runs to the positive terminal of the battery
2) Negative battery cable that runs from the battery to the vehicles chassis
3) Chassis grounding cable that runs to the engine block

http://www.powerstroke.org/forum/6-...forum/6-0l-performance-parts-discussion/278619-lookin-4-big-3-upgrade-pics.html

 

Had the alternator tested and replaced yesterday. Was only putting out 11-12 volts on the bench, intermittently going up to 13. I still have to load test the batteries, as I was pressed for time yesterday.

The various cables looked good, though I re-cleaned the one positive terminal. Looking forward to seeing if it corrodes again.

 

Your alt and or voltage regulator is toast.

 

Load tested the batteries today. Driver's side **** the bed. They tested good at the end of January, so it died between now and then.

What do you figure killed what? Did the batt die and drag the alt down with it, or did the alt die slowly and end the one battery in the process?

Also, would low voltage kill glowplugs?

 

Normally the pass side eats it first. Some people rotate their Batts every 6 months or so. Replace both Batts and alt and you should be good for a while.

 

Yea I rotate mine regularly. The one that died was both older and was a lower tier battery. I was expecting it to go for awhile now, which is part of why I load tested them in January.

I read ages ago that the alt doesn't start charging the batteries right away; and, that there was a way to rewire the charging system so that it both starts charging both batteries equally right away. Is there any credibility to this? Was that the link Heavy posted earlier?

 

The big 3 kit helps especially if you get a higher output amp alt.

When you first start the truck you should see around 14v from the alt. Once the truck warms up and the glow plugs turn off you will see the alt output voltage drop back down to their normal values of 12.5 ish.