Checking charging system with a multi meter

Unknown
Unknown
edited November -1 in HUDSON
There was an article (WTN?) on how to check your charging system using a multimeter. My amp light is staying on and I need instructions on what terminals to connect to to see if I have a bad generator, bad VR or bad light.

Help is appreciated.

Pat

Comments

  • RonS
    RonS Senior Contributor
    Check all your conections from the amp light to the ignition switch and to the A terminal at the regulator.Is the bulb burned out on the dash? Is the battery running down? Do you still have the 6v with a generator? Place meter leads, +to+, - to -, on batt terms (Engine off), should read @ 6.2 -6.5 or so. Start engine, raise RPM to @1250( above cutin speed) voltage should rise showing a charge of @7.2v. If no charge , we need to find the culprit, generator or regulator? Put a jumper wire lead to the field terminal on the generator, then ground the other end of the lead. If the meter shows a charge rate increase then the regulator is the problem. No increase in charge rate,the generator is the problem. Also, make sure the regulator unit has a good clean ground to the body via the sheetmetal screws, or however.
  • Park_W
    Park_W Senior Contributor
    Pat, Ron's guidance is good. This in addition: what year model is the car? That makes a little difference in how the GEN lamp works. But in any case, the lamp is powered from the ignition switch and is grounded down at the voltage regulator in one of two ways, depending on the vintage of the car. So one more source of your indications could be that the GEN lamp wire could be grounding against the body or chassis somewhere between the lamp socket and the VR.

    This is more likely on the older cars, which have a separate terminal ("T") on the VR for the GEN light. On the later ones the GEN lamp wire just goes to the "A" terminal on the VR. That arrangement works because when the gen isn't putting out, the armature is pretty much a dead short to ground. Then as gen output rises, the difference between what it's doing and what the battery's doing is less and less, so the lamp gets dimmer, and when the contact ("cutout") relay in the VR closes, the armature and the battery are directly connected, so the GEN light goes out completely.
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