Dim lights on idle

[canuk]

Can anyone help me with my low voltage on idle problem? when my 68 charger 440 idles , the lights dim,I tried setting idle higher , helped a bit but it should be much better than it is. the battery is good and so is the alt, All is well over 1100 rpm, thanks

 

[69 Runner]

I don't mean to not answer your question, but if you take a look around, you will find that this issue has recently been discussed. You'll get some ideas for this, and other issues you may be having.

 

[1badstroker]

This may help.

The headlights (and all of the other lights on the car) go dim for only one reason, that's because the system voltage drops below the normal voltage of 14 volts. Voltage is electrical pressure just as water pressure makes the water come out of a faucet. The greater the pressure (voltage), the faster the water comes out. Loose the pressure (voltage) and the water come out slower. Loose electrical pressure and the lights get dimmer. Amperage is electrical volume and since your headlights and standard electrical options are less than the amperage (volume) capabilities of the alternator, voltage should remain in the normal range (14 to 14.4 volts). So, why does the voltage go below normal? First thing to be sure of is that the wiring is not restricting the flow of current to the system. This can be done using a digital voltmeter. Connect the positive(+) of the meter to the battery stud of the alternator and the negative (-) of the meter to the POSITIVE of the battery. Run the car with the lights on (to create a load) and read the meter. You should not read more than .3 to .7 (that is tenths) of a volt. Do the same with the negative side of the charging system. Connect the negative (-) of the meter to the alternator case and the positive (+) of the meter to the NEGATIVE battery terminal. More than that and you have wiring that is not allowing normal flow of electricity. (Hint, did you check the bulkhead connector for a hot or burned connection?)

Now for the more probable cause of your problem. The same type of Chrysler alternator was used for many years and all had the same physical shapes. However, the electrical characteristics changed over the years. Before 1969 the alternator was a rather low output (37-42 amps) and was used with a mechanical regulator. The rotor installed in these alternators had a field current of 2.3 to 2.7 amps. In the later 70's the windings in the rotor was changed and had a much higher resistance. Over the years the alternators have been rebuilt so many times that the rotors generally don't get tested for the correct application and a higher amp rotor could be installed in an alternator that it was not designed to be in. A higher output alternator will give you more amperage capacity, but only at higher engine RPM's and will usually not do as good as a lower amp alternator at low engine RPM's. Later model high output alternators are designed to give good output at low & high RPM's and the engine idle is usually 200 -300 rpm's higher than your classic car. So the moral of the story is that there is a good possibility that the alternator on your car was not rebuilt with the correct parts to operate as it should on older cars. If the same alternator was installed on a 70's car with an electronic regulator and a few hundred higher engine RPM's, you would never have a problem.


I hope this helps with your problem.

 

[canuk]

Thanks again

Was looking at some old threads and came across your response again. I didnt see a thank you anywhere . I must have opened it read it and forgot to thank you. I feel terrible about this . Your advice helped a lot and took care of my problem. Your time and effort were greatly appreciated and I would like apologize . Vern

 

[Cranky]

Wow...all these years I've been messing with these cars and had no idea about that...thanks for the info!

 

[SUPERSTOCKRACER]

I have ADD so i didnt read that last long thread but if you want to have steady voltage and no more dim headlights. Go to autozone and get a new electronic solid state voltage regulator. problem solved for $25.00