[Blas]

17.5-18v is pretty high and would toast a battery if it got to it. You would smell the battery boiling in the trunk when you opened it (off-gasing)
Easist thing to do is call me. I'll send my daytime/ evening phone numbers in a PM. Too early to type - no coffee yet.

Ok, I had coffee:
Short version: If all else is in order, (grounds, connectors, etc) replace the diode on the fuse panel - (radioshack)

Quote from my Wiring Diagram Note:
Diode function: (type IN5408)
The Diode allows power to the blue w/white tracer wire going to the regulator.
Symptoms:
The car just quits charging.
Testing: "A jumper wire can be used to test operation but disconnect the wire before shutting the car off or you could get a backfeed through the ignition switch and the car won't shut off."

As to the comment about rewiring your car.
This wiring has been done 2 ways.
The early design: The power came from the alternator via the voltage regulator via a 4mm red wire which connected to the hot side of the starter solenoid on firewall. This sent charging power on to the battery by way of the BIG red cable under the car connecting to the battery. Another 4mm red wire came from the hot side of the starter solenoid on firewall and went to the AMP meters input , all of which passed thru the AMP meter (so the meter can sense the cars amperage use) and then into the cars wiring harness - feeding the cars power users. Note: there is no fuse in this early design. This applies to cars up to chassis #1039.

Now a redesign of the wiring harness occurred (cars #1040+) and the addition of a drop down fuse panel (among other things) Now included on the new drop down panel is a post where the above mentioned alternator/voltage regulator power supply 4mm red wire connection was relocated to. (from the starter solenoid on firewall) From this new post, one 4mm red wire went back out to the starter solenoid on firewall, which sent charging power on to the battery like the earlier design, and a second 4mm red wire when on to feed the car thru the AMP meter as it did in the earlier design. But note the addition of a master 80 AMP fuse in the new design.

The difference being where the wire from the alternator/voltage regulator is connected. And this is what I believe to be the difference in your wiring and the wiring diagram is related to. I never saw the logic in coming into the car and then back out to the engine compartment with the charging wire. But both ways work.


Another person commented:
"...The ohm meter reads 0.00 ohms." Odd...that's an open circuit. No power would be going to feed cars harness thru that fuse???

Another person commented:
Great: 12.7v is a fully charged battery with engine NOT running. should have the same voltage at hot side of starter solenoid on firewall too. Now with the car running both of these voltages should go up to 13.8v-14v max at 2500rpm. Much less and the car won't charge properly - More and you'll toast the battery.