Voltage Regulator Testing?

[mopowers]

Is there a way to test this single field voltage regulator?

 

[KitCarlson]

Yes. If you have a variable power supply here is a simple way to bench test. Place a 12V bulb test wires on field terminal of regulator and case ground. Place the + supply lead to ignition terminal of regulator, - to case ground. Start at 12V, the bulb should light, increase voltage to 14.5V, the bulb should go out. By slowly changing the voltage you can determine the operate point.

 

[mopowers]

Yes. If you have a variable power supply here is a simple way to bench test. Place a 12V bulb test wires on field terminal of regulator and case ground. Place the + supply lead to ignition terminal of regulator, - to case ground. Start at 12V, the bulb should light, increase voltage to 14.5V, the bulb should go out. By slowly changing the voltage you can determine the operate point.

I don't have a variable power supply. This may be a stupid question, but could I instead hook a lead from my truck battery to the top ign terminal with the truck not running and test it, then start the truck and test it again since it will then be about 14.2V?

At what voltage should the VR not turn the test light on.

Lastly, I assume I touch the light to the field terminal on the VR? Is that correct?

 

[67Dart273]

Best way is just test it on the car

1.....What makes you think it's not?

2....Start by getting car warm and battery "normal." You still have an ammeter? It should settle down to "0" after charging up, at a fast idle. Then still on fast idle, hook a meter up right to the battery posts. Should run no less than 13.5, and no more than 14.5. Optimum is 13.8-----14.2

3....If voltage is low in above test, might be alternator. Try unhooking VR, and jumpering the two wires previously hooked to the VR together. This will "full field" the alternator causing it to charge maximum

Start engine, watch ammeter and voltmeter. Slowly bring up RPM. Voltage and amperage should go up. Try to keep below 15V. Turn on headlights, heater, any heavy load. Bring up RPM to fast idle or a bit more. Voltage should climb back up, and you should be able to come up above 14. If not, you have alternator or WIRING troubles

4....If charging voltage of a normally hooked up system is HIGH there can be several causes

Most likely is voltage drop in the ignition harness, "the path" from the battery to the VR IGN terminal.

Also, could be voltage drop in ground circuit. VR MUST be grounded to "same as" battery negative.

Could be VR out of calibration

Rare, but a bad battery can cause this as well

 

[KitCarlson]

I would follow what Del suggests, it is good way, and it tests the whole system with what you have.

 

[mopowers]

Best way is just test it on the car

1.....What makes you think it's not?

2....Start by getting car warm and battery "normal." You still have an ammeter? It should settle down to "0" after charging up, at a fast idle. Then still on fast idle, hook a meter up right to the battery posts. Should run no less than 13.5, and no more than 14.5. Optimum is 13.8-----14.2

3....If voltage is low in above test, might be alternator. Try unhooking VR, and jumpering the two wires previously hooked to the VR together. This will "full field" the alternator causing it to charge maximum

Start engine, watch ammeter and voltmeter. Slowly bring up RPM. Voltage and amperage should go up. Try to keep below 15V. Turn on headlights, heater, any heavy load. Bring up RPM to fast idle or a bit more. Voltage should climb back up, and you should be able to come up above 14. If not, you have alternator or WIRING troubles

4....If charging voltage of a normally hooked up system is HIGH there can be several causes

Most likely is voltage drop in the ignition harness, "the path" from the battery to the VR IGN terminal.

Also, could be voltage drop in ground circuit. VR MUST be grounded to "same as" battery negative.

Could be VR out of calibration

Rare, but a bad battery can cause this as well

Thank you! I actually sent you a PM before seeing this post. You can disregard my PM. I appreciate it help. I tested the battery voltage while running and it was low at 12.9V.

I don't have an ammeter hooked up. I bypassed it. I will try the full field test and see if that changes anything and report back.

Thanks again, sir.

 

[BillGrissom]

For the future, a cigarette lighter voltmeter is good for diagnostics while driving, to help insure you aren't stranded on long trips. I use in all my cars. $15 Amazon, $5 HF. You should see ~14.3 V on the highway. I also have a Black & Decker charger with an "alternator test" button. I think it simply looks for a pulsing sine wave that indicates "alternator alive on the wire", so is just a screening tool.

Unlikely your Vreg is bad. More likely is wiring and connections. One common problem is that the case of the Vreg doesn't have a good ground to the body (thru mounting screw). I use a separate ground jumper. A multimeter can check all those things, looking for unwarranted voltage drops.

 

[mopowers]

Last night I connected the 12v ign wire at the VR and the field wire at the voltage regulator. When I brought the RPMs up, voltage at the battery went up past 15. So I guess that means the alternator is working.

I also checked the battery voltage at idle which was 12.8. When I brought the rpms up, it went up to 14.5. Looks like everything is working, right?

Maybe there's a draw somewhere in the system.

 

[Sedanman]

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