Lights go dim and bright

[BIGRED64]

Looking for some help with an issue. When the turn signals or brake pedal is used..all dash and running lights will dim out. The dim and bright will follow the turn signal flash or the on and off of the brake pedal.
All lights work properly untill either of the above actions are taken. Car is a 1964 Polara. Any help would be greatly appreciated. Thanks

 

[67 coronet]

first,do you have a good ground strap for your eng?
second,have you checked alt output?
third,you might switch to solid state voltage regulator if you dont have one already.

 

[440roadrunner]

Start by reading this article:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

more where this came from

http://www.madelectrical.com/electrical-tech.shtml

The next thing is, "the alternator"

The older "roundback" alternators do not put out nearly as well at lower RPM as the newer "squareback" type. You might consider asking for a 45-55 or so and make SURE it is a squareback. This will have TWO field terminals, so to hook this to your old 69/ earlier regulator, you'll need to ground either one of the two field connectors

You can also, of course, add just one wire, and convert to the 70/ later regulator.

example of a "squareback"

The "usual stuff"

You might have one or more bad diodes, turning your 35A into a 15A, or your 45A into a 20A, etc. So test the alternator for output. Read the shop manual

Someone might have put a larger pulley on the alternator slowing it down

The pulley might be glazed, slipping, or the belt might be worn/ loose

Try a few tests

1---Check for voltage drop in the ignition circuit which also supplies the regulator. Turn the key to "run" engine off. Hook your meter to the IGN terminal of the regulator, and to the battery stud on the regulator. With the meter set to low DC volts, you should read a VERY low reading the LOWER the BETTER. Over .3V (three tenths of a volt) shows a voltage drop problem in the harness. This will actually cause OVER charging at higher RPM

2--check the regulator ground. To do that, get engine running at an RPM to simulate "medium cruise" As above, low DC volts, stick one probe on battery NEG post, and the other directly onto the regulator mounting flange. Again, you hope to see almost nothing for a reading

3--With the engine still running, check battery charging voltage. With the engine/ regulator warm, you should see 13.8--14.2, and in no case more than 14.5, nor less than 13.5

4--Check for voltage drop in the alternator output lead. Clip one voltmeter lead to the alternator output stud. Clip the other lead to the starter relay battery stud. Now turn on some loads, lights, heater, 4x flasher. You hope to read less than 1/2 volt. If you get a reading approaching 1 volt, you have voltage drop problems in the charging wire. I defer to the MAD article posted above.

Your top suspects for voltage drop problems in these old girls are A--poor connections in the bulkhead connector, not only the charging line, but the headlights and ignition circuit. B--poor connections at the ignition switch connector or the switch itself. C--Poor connections in the headlight switch or the switch itself, as well as same at the dimmer switch, and again, bulkhead. Also check the headlight grounds out at the headlights as well as condition of the headlight connectors.

 

[Dako]

I agree, in that it is likely 'ground' related. A common thread I see here is that turn signals and brakes are both associated with the dual element bulbs in the tail lights. If you pull one (or both) bulbs, does the dimming go away? Along with what 67 Coronet suggests to look at, look for corroded or dirty bulb sockets, or a defective bulb(s). If not there, then maybe the wires and/ or the connections to them? Not saying this is it...just another thing to check. Good luck!

 

[BIGRED64]

Lights go dim

Looking for some help with an issue. When the turn signals or brake pedal is used..all dash and running lights will dim out. The dim and bright will follow the turn signal flash or the on and off of the brake pedal.
All lights work properly untill either of the above actions are taken. Car is a 1964 Polara. Any help would be greatly appreciated. Thanks

Thanks for the quick reply....

The engine has 3 grounds plus a solid motor mount.

Solid state regulator.

Alternator has been checked to be ok.

 

[RustyRatRod]

With the older alternator and regulator, some of that can actually be considered normal. So, if you check everything out and it's good, you may not have reason to panic. Of course, you can always upgrade the electrical system (not a bad idea on a Chrysler product) to the later alternator and regulator. That will help greatly.

 

[67 coronet]

any added electronics?like fuel pump ,fans,or big radio.could be a bit too much power for your alt.

 

[super-bee_ski]

This data above is "ALL GOOD STUFF"
Thank you...
"super-bee_ski"

PS: I've got a "round back" and a "square back" and I think I'm running the "square back" on my 70 Bee.

 

[BIGRED64]

Lights go dim

Thanks for the quick response to all. I will follow up and report back.

 

[BIGRED64]

Lights go dim

Electric fuel pump, cooling fan, MSD and Mopar ignition box are being used. I did not state that this problem is at at both running and at engine off position....taking the big "loads" off the sys.

 

[440roadrunner]

...........Solid state regulator............ Alternator has been checked to be ok.

So is this the 70/ later isolated field type, and do you have a squareback alternator? How large (amperage) is the alternator?

Electric fuel pump, cooling fan, MSD and Mopar ignition box are being used. I did not state that this problem is at at both running and at engine off position....taking the big "loads" off the sys.

I don't understand, "engine off". If the lights are dim "engine off" it's simply "on the battery." Or do you mean they are actually flashing more on/ off?

This sounds like the breaker in the headlight switch is cycling. IF this is what is happpening, this can be a number of things

Bad connection at the headlight switch connector, causing heating in the connections, which heats up the breaker

Breaker itself going bad, getting "weak" or bad contacts.

You may have larger wattage headlamps, causing more current, and premature breaker tripping.

Is this a rythmic cycling up/ down, or on/ off?