1970 Cadillac electric light flickering-FIXED

[Scot Minesinger]

For the nine years I have owned my 1970 Cadillac the lights flicker.  That is according to my voltmeter the voltage goes from 13.7 to 13.9 VDC and the lights vary slightly in brightness.  It is noticeable easily when car is driven into garage at night.

It got bad lately and according to volt meter it was varying 13.5 to 15.5 Volts, and so I replaced voltage regulator and it went back to 13.7 to 13.9 volts.

The car is fairly stock electrically.  I have the voltmeter on it, an alternator rebuilt to provide more amps at idle so voltage stays 12.5 when top is raised or lowered.  It seems that about every 18 months I go thru a voltage regulator, which no big deal almost consider it maintenance.

Still I'm sure it is not right.  Does anyone know why this is happening and how to fix it?

[chrisntam]

Scot, can't help you too much, but would like to clarify your question.

Are the headlights flickering or all the lights in the car flicker (dash lights, courtesy lights, etc.)?  Does the flickering only occur when the car is running?  What about disconnecting the alternator (electrically) and start the car to see if that changes anything?  Not sure if there are consequences in running the car w/ the alternator disconnected or not.  Just brainstorming to try to rule some things out.

You might call these guys or look in their FAQs to see if they can help:

http://www.lectriclimited.com/mainpage.htm

scroll down on the left hand side under the "technical" area.

I looked thru their website and my take away was that automotive wiring has a useful life and the wiring in our car's useful life is long over............But this is info provided by the folk that sell the wiring.  Much like asking a barber if you need a haircut.  Of course you need a haircut!

chris.

[Jeff Rosansky CLC #28373]

Great suggestion to check it with the engine off.  Do you have a points type regulator?  My guess is that is the points opening and closing.  The question is what is causing it.  Ground issue somewhere I would think.

See if it does it when the car is off.  If not then disconnect the regulator and try it, then disconnect the alternator.  Need to isolate what is causing the problem.
Jeff

[Glen]

From the clues provided we can rule out the regulator as it has been replaced and we can rule out the alternator as it has also been replaced.  All that is left is the wiring.  Check all the connections to be sure they are clean and tight and pay particular attention to the grounds. 

I find the system works best when the regulator is set to 14.2 volts.  But if you are driving more long distance maybe the lower voltage is OK. 

[Scot Minesinger]

Great suggestions to get me started, any more would be appreciated.

To clarify problem it is all lights, headlights, glove box and etc. 

The problem has been there with different starters, alternator, and voltage regulators.  The voltage regulators tend to fail (voltage fluctuates 2 volts instead of 0.2 volts) after 1.5 years or so, supposedly got a good one this time-we will see.  I will add that replacing the voltage regulator does not change the flickering, and only makes my volt meter show an improvement.

The car has always had electronic ignition, points removed.  I must say that it made no difference in the way the car ran contrary to advice of people who installed it, and probably would not do that again.

Further, just replaced battery cables and cleaned up all the grounds.  Ground form starter to frame cleaned and re-done, ground from engine block to sheet metal cleaned and re-done, ground from battery to sheet metal cleaned and re-done, and ground from battery to frame cleaned and re-done.  Also installed one of those real good rotary 750 amp disconnect switches to interrupt ground from battery.  All this ground work made no improvement. 

[joeceretti]

Sounds like not much left except maybe the light switch.

[chrisntam]

Sounds like not much left except maybe the light switch.

But the light switch only controls the headlights, running lights, dash lights and sometimes, the courtesy lights.  Pick a light not controlled by the headlight switch (trunk light) and see if that flickers.  The common denominator is the headlight switch for most of the lights we see at night though.  Are there other circuits that have lights on it not connected to the headlight switch?

Not really adding anything of substance here, just brainstorming.

[TJ Hopland]

Not sure when they made the changes or the exact routing on a 70 but a little later they used the big terminal on the starter/solenoid as the main power junction.  That is an area that gets some road grime and heat and often not the easiest to work on so its a good place to start looking for electrical quirks.   Some years in the early 70's they also had a connector about a foot up in the harness from the starter.  Again a good place or issues due to location. 

Its been a while since I dealt with an external regulator but I would look at where / what it uses for a 'sense' signal and its ground.   If its not got a good ground or a good sense signal it can't do its job properly.   

Grounds are always a place for issues too.   Since this is apparently fairly consistent try using jumper cables to add grounds between the body, engine, and battery.   IF adding those grounds helps you know where you have to look.   

[Scot Minesinger]

The starter power connection is very good, because when starter was replaced, connections were cleaned.

The lights do not do this when car is off

Need to investigate further, will keep you all apprised, I'm sure this is not the first car collector this has happened to.

[Coupe Deville]

Did the lights do this before you had the altranator rebuilt?

[76eldo]

It's going to be bad diodes in the alternator.
Alternators make AC current and the diodes and a bridge rectifier and other things in the circuit change it into DC to charge the battery and run the car.

If its rapid flickering its the alternator. Replaced does not always mean fixed.

Brian

[dplotkin]

Your problem is in the alternator. one or more defective diodes, worn slip ring/brushes or a bad winding in the rotor or stator.
Had the same problem on an Impala. Put a Power-master alternator on it (exact replica).

Dan

[Jeff Rosansky CLC #28373]

Actually, I don't think you can rule the regulator out--Per se.  In other words, I think flickering is caused by the regulator's points opening and closing.  The question is, why.  It could be the alternator as stated above.  I don't think there is a problem with the regulator, but some draw on the system that is causing this.  At idle, with the lights on, the system is drawing more than the alternator is putting out.  We all see this when we are at a stoplight and the lights, blower, etc show signs of low power.  Then when we hit the gas, they all go back to normal.  This happens every day.  What, however, is happening here is that the regulator is not allowing the battery to 'trickle' charge.  It is charging well, or not at all--- This is what we need to figure out. 
The fact that you keep going thru voltage regulators shows that there is a valid problem here.  The alternator may be spiking.  How old is the battery?  Is there any resistance in your cutoff switch?  Excessive resistance in the battery or its cutoff switch may be an issue.
Disconnect the charging circuit and run the engine.  I bet the lights don't flicker. 
Jeff

[Scot Minesinger]

The lights do not flicker when car is off and lights are on.

The lights appear to flicker at same speed as alternator, so when you give it more gas it flicker so rapidly it is more difficult to notice (say 2,500rpm), it is noticeable easily at 2,000 rpm and less.

This has been going on with different combinations of regulators, alternators and batteries. 

Note that although the voltage regulator was replaced because voltage was varying by 2 volts just last week, and after replacement voltage fluctuation went back to 0.2 volts fluctuation, the flickering remained about the same.

Internet search yields either bad fuse-able link, which is easy to check (and I hope but doubt this is it), or bad wiring-which makes sense, because it will be a pain to find.

[Jeff Rosansky CLC #28373]

Just run jumper wires to/from the regulator and see if that helps.  Bypass the wiring harness altogether. 
Just for grins, can you switch batteries between cars?  A battery issue would cause resistance when trying to charge.  Maybe enough resistance to prevent a trickle charge.
Jeff

[Scot Minesinger]

Finally found it thanks to Lynn Gardner (his suggestion as to where to look via private message).  It was the connection of the crappy gray connector into the alternator.  My car had been converted to internal regulator and I converted it back.  I bought the gray connector as an aftermarket part (not original), and whine, whine, whine, - it was bad.  This fried my amp in the dash climate control, so now I can fix that too - yes another rich experience.  No more flickering!

[joecaristo]

Glad you fixed it. Thanks for posting the solution.
Joe