Low voltage during idle and when reving.

[68wanabee]

I have 68 Dodge Coronet with 440 and HEI etc. I do not have the power that I think the car should and after looking at carburetor, wires, plugs etc. I began checking the charging and at idle I am barely making 12 volts and when it revs it does not change much. The alternator is new and I have read on many other posts that the bulkhead is a culprit in many posts. One of the checks is to disconnect the battery while at idle and the car should still continue running and what should the voltage be when battery disconnected assuming it should be over 13.6 or more? Also, what else can I disconnect that might help to determine what could be drawing down or not allowing the charging system to operate properly.
Another issue is the ballast resistor get extremely hot. What sort of voltage should I see on either side of the ballast resistor. What voltage should I see on the voltage regulator on either side? What about at the + of the coil?

 

[68wanabee]

I disconnect the battery while car is running and the car dies, so I have some charging issues. Replaced alternator with a known good alternator and still having the same problem. I am surprised that no one has any feedback, I have seen other threads with common issue and everyone talks about grounds, I have checked grounds and cleaned all connections on the firewal to bare metal with no luck. Would replacing the voltage regulator fix this problem? Also, thinking about disconnected the after market Volt/Ammeter to bypass in case it is drawing something down in the circuit.

 

[Pops1967GTX]

Ballast resistor get extremely hot. That’s normal......Are you burning out the resistor? the wrong coil, or a damaged coil can cause excessive heat....Also smoke is normal for a new resistor when replaced....If you're not charging, then you need to do some checks , don’t change parts until you test.....
Does the ballast resistor have 2 pins or 4 pins. ?Is it matched to your electronic ignition? 12V to the coil while cranking & then going through the resistor for about 9V while running?


information sites.........
http://www.classicwinnebagos.com/forum/index.php?topic=3424.0


http://books.google.com/books?id=rt...1#v=onepage&q=ballast resistor testing&f=true

http://randysrepairshop.net/interpr...chrysler-charging-system-1978---1990-fwd.html


http://www.moparmusclemagazine.com/...110_ballast_resistor_guide_ballast_blast_off/

http://www.youtube.com/watch?v=6IJKCOlTywg&feature=related
http://www.youtube.com/watch?v=Oitv2djx_Wg&feature=related
http://www.youtube.com/watch?v=aYfkGx2vIrY&feature=relmfu

TROUBLESHOOTING---BOOK----
This test will determine whether or not the system is charging the battery and, if not, whether the alternator or regulator is at fault. It requires a voltmeter capable of measuring at least 16 volts, down to tenths of a volt.
If the charging system on your car has an externally mounted regulator, warm up the engine before performing the following test:
1. Turn off the engine, lights, and all other accessories.
2. Attach an engine tachometer according to the manufacturer’s instructions.
3. Connect the voltmeter to the battery by attaching the positive lead to the positive terminal and the negative lead to the negative terminal.
4. Note the voltmeter reading. If it is less than 12 volts, charge the battery. Then note the voltage reading again and record it.
5. Start the engine and slowly increase the speed to 1,500 rpm.
6. Note the voltmeter reading again. If it exceeds the engine-off voltage by more than 2 volts, the system has a faulty regulator, a poor regulator ground, or a short circuit in the wiring between the alternator and regulator.
7. If this voltage reading exceeds the engine-off voltage by less than 2 volts, perform a load test.
LOAD TEST
1. Keep the tachometer and voltmeter connected as they were for no-load test.
2.Note and record the voltage reading.
3. Start the engine and turn on the heater (or air conditioner) at high speed. Turn on all lights and accessories.
4.Increase the engine speed to 3,000 rpm and note the voltmeter reading.
5. If this reading exceeds the engine-off voltage by 1/2 volt or more, the charging system is functioning properly.
6. If his reading exceeds the engine-off voltage by less than 1/2 volt, perform a full-field test.
FULL-FIELD TEST
When the regulator’s control function is bypassed, the alternator runs full-field. The method of bypassing the regulator differs, depending on the type of vehicle. For this reason, Step 1 of the full-field test changes from car to car, while the remaining steps are the same for all models.
1C. Chrysler models. Turn of the engine. Locate the green wire connecting the alternator field terminal to the regulator; disconnect this wire from the alternator. Connect a jumper wire from the alternator field terminal to a good ground.
2. Once the regulator has been bypassed, repeat the load test.
3. If the full-field voltage exceeds the engine-off voltage by 1/2 volt or more, the regulator is defective and must be replaced.
4.If the increase in the voltage is less than 1/2 volt, either the alternator or wiring is faulty.
5. Inspect the wiring for signs of wear or heat damage.
6. If the wiring looks good, the alternator is probably the faulty component.


The Quick and Dirty Charging System Test

Remove the (+) FLD wire from the alternator.
Put a temporary jumper wire from the same (+) FLD terminal to the large output post on the alternator (battery +).
Start the car and see if it charges. If it does… good alternator. If not … bad alternator. If it did charge, then the voltage regulator is the problem child.
Turn the ignition key to the on position. Check for power on the small IGN terminal of the regulator. If there is, then see if there is any power on the other voltage regulator post to the alternator. A bad ground on the voltage regulator case is a very common problem. If not then you need to chase down the IGN power issue.

 

[68wanabee]

Pops,
Thanks for the information and I will follow through these tests. I have changed the alternator based on being tested at the auto store, but after replacing still same problem. But now I have something to go by and will run through and post my findings or the fix to the problem. This is most excellent information and appreciate your time in responding.

 

[68wanabee]

I forgot to mention the ballast resistor I have is currently a 2 Pin resistor with the electronic ignition upgrade.

 

[Photon440]

Do the suggestions from Pops, but don't do what you earlier mentioned - pulling a battery cable while the engine is running. That was a workable idea long ago when electrical systems were simple and cars used generators, but it's hard on your alternator. An open circuit spikes the voltage and you run the risk of blowing some or all of your alternator's rectifier diodes.

And while you're not in danger as you would be on a newer car of damaging the cpu or any of the other sophisticated electronics that are now used, you still run the risk of damaging capacitors or transistors in your dash. A newer stereo system, if you have one installed, would be at risk as well.

One of the uses of the battery, besides the obvious storage of electricity, is that it acts as a giant capacitor or buffer for the system and smooths out the half waves that the rectifiers are churning out as they convert AC power to DC. Leave it hooked up.

-=Photon440=-