New batteries, new altenator, low voltage... Again!

[LiftedBlackHD]

I started a thread a couple weeks ago about a low voltage issue. I replaced the batteries and the problem continued. I then replaced the alternator and my voltage went up to about 13 and all was well.

Here we are a couple weeks later (driven truck maybe 5 times) and the battery light comes on. Voltage is reading about 11.6 to 11.9 on my SCT.

My guess is bad alternator... What say you?

 

[G Racing]

It's not uncommon to get a new or rebuilt bad alternator. I would also double check the hot wire from the alternator where it connects to the battery. Also make sure the found wire at the block is tight and clean.

 

[Fordguy100]

What is the battery voltage at when sitting? I would test batteries and alternator, then do a draw test.

 

[Lethalthreat7.3]

What condition are the battery cables in? The passenger side pos cable is notorious for corroding internally and causing premature alternator failure from excessive charging amperage. Try using an ohm meter on the lowest scale(200) and see if there is resistance in the wire from corrosion.

 

[LiftedBlackHD]

Ok just tested the batteries and alt. with the truck off im getting 12.1 at passenger side battery, 12.1 at driver side battery and 12.1 at the alternaor.

With truck idling passenger side drops to 11.9, driver side drops to 11.8 and alternator at 11.9.

SCT still reads about 11.6.

 

[G Racing]

Alternator is bad. Should be over 13v running.

 

[LiftedBlackHD]

Alternator is bad. Should be over 13v running.

Thanks. Looks like I'm going to have to take it off and go for round #2.

 

[Mdub707]

You should try reading the batteries individually... they're always going to read about the same when they're connected to each other.