Bad alternator?

[OneofFew]

I'm not getting any alternator output. I started the car, noticed it was not charging, test drove and it started charging. After restarting engine, no charge. I wiggled wires, checked connections and grounds, no change. I unplugged the 4 prong, 2 wire connector at the back of the alternator (engine running) and I am getting 10.5v on the brown wire, 0.5v on the yellow. Plugged in, the brown wire puts out 1.3v. Battery voltage 12.4, 12v running.
Using a test light from B+ to the pin on the alternator that gets the brown wire, the test light lights up.

Does anyone know any other checks I can do to verify it is not a control circuit?

I do have a SUN Vat60 tester, but have never used it to check diodes.

 

[Big Mama]

How old is the battery? Do you have an advanced or auto zone you can have test it free?

 

[HiHoeSilver]

I'm not getting any alternator output. I started the car, noticed it was not charging, test drove and it started charging. After restarting engine, no charge. I wiggled wires, checked connections and grounds, no change. I unplugged the 4 prong, 2 wire connector at the back of the alternator (engine running) and I am getting 10.5v on the brown wire, 0.5v on the yellow. Plugged in, the brown wire puts out 1.3v. Battery voltage 12.4, 12v running.
Using a test light from B+ to the pin on the alternator that gets the brown wire, the test light lights up.

Does anyone know any other checks I can do to verify it is not a control circuit?

I do have a SUN Vat60 tester, but have never used it to check diodes.

Does your truck have RVC?

 

[Doubeleive]

extremely unlikely to be anything other than the alternator, 12.4v is battery power only, you should be getting 13v+

 

[Big Mama]

Mine’s 14.4 for comparison

 

[OneofFew]

Update: I took the alternator out and had it bench tested. Failed. I chose a reman Ultima unit with lifetime warranty.
The new unit charges at 14v.

 

[Big Mama]

Great thanks for closing the loop for the next guy

 

[89Suburban]

Update: I took the alternator out and had it bench tested. Failed. I chose a reman Ultima unit with lifetime warranty.
The new unit charges at 14v.

Than thanks for the update!

 

[OneofFew]

Follow-up: In my efforts to check for loose wires, I removed to cover off the ECM (next to the power steering pump. Now I cannot figure out how the cover goes on there. can anyone snap a picture?

 

[Fless]

Does this help?