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Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 14324
Experience:  Toyota Master Diagnostic
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I replaced the alternator on my 2015 sienna /c the old one

Customer Question

I replaced the alternator on my 2015 sienna b/c the old one "old, ha!!" Was only putting out 13.7 volts and I was told it should be 13.9-14.2.
JA: Have you checked all the fuses? Do you have a wiring diagram?
Customer: Now the new alternator is supposedly putting out zero Volts!! Which I know is basically impossible.
JA: Are you fixing your Sienna yourself? What have you tried so far?
Customer: I do not have a wiring diagram
JA: Anything else you want the mechanic to know before I connect you?
Customer: Yes, fixing it myself. It was supposed to be a simple part swap!, but now I'm at a loss. I did check all the fuses, and the battery is brand new. It's reading 12.3 volts.
Submitted: 15 days ago.
Category: Toyota
Expert:  Skyvisions replied 15 days ago.

When the engine is running what is the voltage at the battery? What is the voltage of the large cable at the alt? Honestly the 13.7 on the old alt is normal and consider good not sure why someone told you it was not. The voltage is not the issue it is current flow ie AMPS.

Customer: replied 15 days ago.
With the engine running, the voltage of the battery is 12.3 volts. I'm not sure which cable I should be checking from the alternator? There's one large cable which appears to be a grounding cable and then there's a four pin connector
Expert:  Skyvisions replied 15 days ago.

The large cable is the main output cable that goes directly to the battery through a large fuse. Is there any voltage to that large cable with the 10 mm nut on it? Check that with the engine off.

Customer: replied 15 days ago.
With the engine not running the battery reads 12.7 V, and at that large cable on the alternator I'm only reading 2 volts. There's definitely a disconnect somewhere between the alternator and the battery. Could it be that large 140 amp fuse?
Expert:  Skyvisions replied 15 days ago.

Unfortunately I have bad news for you. You have blown the large ALT fuse which is part of a fusible link strip and is incorporated into the main junction/fuse box under the hood. There are no written directions on how to remove that fuse. You have to disassemble the fuse block and remove that fusible link strip which is bolted to the bus bar in order to resolve this problem. That only happens by inadvertently shorting out the large wire from the alternator. Click this link for some illustrations on how it comes apart this is not the exact same fuse block but is similar it'll give you an idea of what you're dealing with. This is not a job for someone who does not have a lot of patience and good at assembling and disassembling things most shops will charge you about two hours in labor to replace this the fuse itself is only about $40.

Customer: replied 15 days ago.
Thank you!!!
Expert:  Skyvisions replied 15 days ago.

You are welcome.

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