2000 S70 can't identify fuse for alternator

lwaldman · Post by **lwaldman** » 03 Sep 2014, 09:43

I am trying to identify the fuse associated with the alternator in my 2000 Volvo S70. Alternator does not appear in the service manuals. The electrical diagrams are difficult to decipher. Does anyone know which fuse in either the main or supplementary fuse boxes is the right one for the alternator? Thanks.

Post by **jimmy57** » 03 Sep 2014, 12:23

There is no alternator fuse for output. The fuse for the D+/61 exciter supply which also serves as charge warning lamp signal would be the fuse for instrument cluster on that car.

Post by **tryingbe** » 03 Sep 2014, 12:45

The main positive battery cable goes from the alternator to the starter, then from the starter to the battery. The is no fuse in that main cable.

What is the issue you're experiencing?

lwaldman · Post by **lwaldman** » 03 Sep 2014, 14:06

Thank you jimmy57 and tryingbe. I put a brand new fully charged battery in yesterday. The alternator appears to be putting out zero current. A mechanic and I are getting the same 12 volts out of the battery as we are out of the alternator. From Volvo manuals and electrical wiring diagrams, I am seeing that 6 of the 9 fuses in the row of fuses designated as 11A appear to be wired indirectly to the alternator, but I'm no expert in reading these diagrams. The other 3 go elsewhere. But, maybe the 12V symbol I'm seeing right next to that row of fuses in the diagram is actually the battery, not sure. If so, it sounds like both of you are right, and we have to replace the alternator. Thanks again.

Post by **regent** » 03 Sep 2014, 16:23

Like it was earlier pointed out, the output from the alternator to the battery bus is hard-wired (not fused) since the alternator has the capability to protect itself from overload or short.

I am assuming the main bus is where you are reading the 12V. What about the voltage at point D+/61? You should check for exciter current with ignition ON to rule out 'hanging' (worn) brushes, or more likely a bad voltage regulator (it is much easier to replace than the whole alt). If the exciting circuit checks good, look for an open in the stator circuits or the rectifiers (replace the alt).