Hi -- my alternator pulley sheared off a few months ago. I replaced the pulley and belt on the old alternator but I am only getting 4 volts of output on the B+ terminal at the alternator. Testing the battery with a multimeter, and getting 12.5V reading before and during engine running. Old alternator was tested at autozone and the machine said it was giving out 14.5V. I even bought a used alternator (OEM BOSCH alternator) and still the same output of 4V at the terminal. Any ideas on how to troubleshoot this? BTW, I had to take off the front bumper, remove the headlamps and put into service mode. Battery light still coming on. Thoughts? Thanks!
Alternator issues with 2014 TDI Jetta sportswagen
- Thread starter RED-VA
- Start date
prsa01
Veteran Member
(nowhere NEAR expert) I have read here that a signal needs to be received at the alternator on one of the other wires for it to produce voltage. I'm also pretty sure these new ones are "smart" and don't just produce a flat 14.5v all the time, or maybe just vary the amperage.
We'll wait for someone knowledgeable to chime in.
We'll wait for someone knowledgeable to chime in.
prsa01
Veteran Member
I would pm Mozambiquer. He does quite a bit with alternators and I think he's been pretty good about helping folks out.
If your get 12.5v at the battery and only 4v at terminal B+ you have a high resistance fault on one of the cables. Check them for corrosionHi -- my alternator pulley sheared off a few months ago. I replaced the pulley and belt on the old alternator but I am only getting 4 volts of output on the B+ terminal at the alternator. Testing the battery with a multimeter, and getting 12.5V reading before and during engine running. Old alternator was tested at autozone and the machine said it was giving out 14.5V. I even bought a used alternator (OEM BOSCH alternator) and still the same output of 4V at the terminal. Any ideas on how to troubleshoot this? BTW, I had to take off the front bumper, remove the headlamps and put into service mode. Battery light still coming on. Thoughts? Thanks!