Bad voltage regulator?

[Bill Crowell]

So the alternator on my '62 Valiant stopped charging the battery. The alternator was producing charging voltage but the ammeter never showed a charge, only a discharge. I traced this to loose connections at the ammeter, which now reads correctly and the alternator is now charging the battery OK. However, when I tightened the ammeter connections, the oil pressure gauge and the temperature gauge started going off the high end of their scales. I'm thinking maybe the bad ammeter connections were masking a bad instrument voltage regulator, which is now supplying the full 12 volts to the instruments, but I'm not sure. Your thoughts?

 

[Joey4speed]

The Voltage Limiter is behind the instrument cluster, it limits the voltage down to around 5V.

The Voltage Regulator is on the firewall, and regulates the Alternator output that charges the battery with < 14V.

BTW, I wouldn't rely solely on the dash Ammeter to determine if your battery is charging properly. Best to use a volt meter across the battery.
Good luck.

 

[67Dart273]

It could be that over-voltage is blowing past the IVR. Basically, to "full field" test an alternator on the pre-70 cars, just jumper the two VR wires together. This puts full 12V on the field, and it should output full tilt.

If it is over voltage / over charging there are several causes in no real order
1...Most common is hot side harness voltage drop. Low voltage to the VR actually RAISES battery voltage, because the VR is trying to compensate This, generally, is bad connections through the bulkhead, at the ammeter, and at the ignition switch
2....A poor ground (VR and batt NEG MUST be the same zero voltage) can also cause over-voltage
3...Bad VR can cause over voltage, especially the older mechanical ones
4....In a few cases a bad battery will cause over voltage. Swap in a known good battery

 

[Mattax]

BTW, I wouldn't rely solely on the dash Ammeter to determine if your battery is charging properly. Best to use a volt meter across the battery.
Good luck.

Good advice.
The ammeter shows battery and charging and discharging.
But when thats not acting normal, its worth measuring voltage produced at alternator and the voltage at the battery. That plus the ammeter can reveal alot.

However, when I tightened the ammeter connections, the oil pressure gauge and the temperature gauge started going off the high end of their scales

It's possible somehow the IVR was bypassed by something you did. '62 arrangements may be a bit different than what we see in later years.

Need to check the wiring diagram in the FSM but wire G5 may also feed the IVR