Alternator/Battery Question

[RandyH]

On my truck, it appeared I lot my alternator, voltage across the batteries (still tied together)was about 12.1, no difference engine started or not. I took the alternator off and had it tested at a starter/alternator rebuild shop and it tested good. Put it back together, still no charging voltage.

I also diconnected the batteries from each other and charged them separately and one took a charge fine, the other appears to not be taking a charge and is staying around 10.8 volts meaning I probably have a bad cell.

Even if the battery is bad, why would the alternator not be putting out? Is there a fuseible link in the system that might be blown? If so, where?

Did the battery cell short and take out a fuse link?

Any thoughts?

Thanks.

 

[rammertide07]

Does it still not charge with a new battery? If a battery is shorted out, it will KEEP everything drained. How do you know the altenator is not putting out when you have it hooked up?

 

[RandyH]

Just getting ready to put two new batteries in. Before, I hooked up just the one good battery and started it with the bad one disconnected, still didn't see anything over the same voltage I had without the alternator running.

 

[Zmann ARGH]

starting with one batt is not smart don't ever do that again ,, in a normal good system the voltage will not jump untill the glow plugs go off ,, typically replace batts in a pair ,, they are not isolated and the weak one will pull the stronger one down

 

[RandyH]

New batteries are in, and everything seems to be working. It was acting funny where I wouldn't see the elevated charging voltage, then I would, then not again. I was starting to wonder whether my voltmeter leads were flakey. I'm guessing that maybe the regulator (in the alternator) is turning off and on as needed to peak the battery.

I also originally thought the batteries were the originals from my Nov04 build date but once I got them out they are apparently the second set of Motorcraft batteries this truck has seen (I've only had it for 2 years) as they are dated 2007. That means that at least one battery in each set only lasted about 3 years. Interesting.

What are the possible risks involved with starting on just one battery?

Zmann & Rammertide - I appreciate your input.

 

[DaveBen]

The single battery can't supply enough current to start your truck under all circumstances. This will cause a large voltage drop and will burn out the starter and other electronics. What you really have is one battery in two places. Replace them in pairs. This is not a place to cheap-out on.

Dave

 

[rammertide07]

I didn't even think it was possible to start a diesel with one battery....or maybe its just the 6.0 that can.

x2 on everything Zmann and Dave said

 

[Ezzie]

I just had to replace both batteries in my 2006. Seems to be the normal lifespan of these things. I checked around for something better to replace them with but even had an independent auto electric guy send me to the dealer to buy the Motorcrafts since they have been the best for this application in his experience.

 

[RandyH]

Wasn't planning on trying to get by on one battery. I've always replaced both batteries at the same time and was just using the one to start it this one time to see if the known bad one was causing the load on the alternator. It actually turned over pretty easily. I put a pair of Die Hard Gold's ($230) in like I had in my '99 previously. We'll see if they last longer than the Motorcrafts. Thanks everyone!

 

[DaveBen]

I tried Die Hards and found they lasted about the same time as the stock Motorcraft batteries. I have not found a battery that will last significantly longer than the Motorcrafts.

Dave