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The Constant Voltage Regulator behind the dash cluster is designed to take the 12V input and reduce it down to a roughly 5V signal. To accomplish that it causes a pulse that if observed with an analog meter you can watch the needle of the meter bounce up and down not quite reaching zero or 12V. It's a fairly quick pulse. I wonder if that might be putting out more than it should be causing the pulse to be visible in the interior lighting and the gauges?
An example of one here on eBay so you can see what they look like. It is possible to pull and test but I use an oscilloscope so I can use the waveform to tell what the 'average' voltage it is putting out is.
I'm not recommending the old analog regulators like that any longer. They make solid-state digital replacements that just put out a steady 5V and can easily be tested. I've run into too many NOS ones that are defective. Probably were tried back in the day and if defective they went back into the boxes and have lingered on shelves for years until someone lists them on eBay!
If your multimeter does True RMS, it should be able to give you an average voltage reading from the CVR. My older multimeter doesn't so I use the oscilloscope - which is really overkill but it does what I'm looking for, and I have it anyway. Plus, it can do so much more...
Update!
I noticed the same color wire going from the fuse box inside comes out to the starter solenoid and then another one goes to the voltage regulator , i also noticed my charging while running was way too low , 11.8 - 12v which i am on a generator but id still too low , so i took it off and back fed the power and seems to not be flickering now , im gonna test the battery and see if its a defective battery. battery is a duralast and its about 5/6 years old if you have any inputs it would be appreciated
I was reading this as well as what others have wrote.
If your not putting out about 14V from the generator at about 1500-2500rpm measured at the battery, this "may" be a part of the problem. When my truck idles, the lights can be on the dim side, then rev it up and I have nice lights when the gen. kicks in. "Maybe" if your regulator for the gen. is cutting in and out, that "may" lead to flickering lights?
Just a thought,
Tom
Last edited by Tom H So. Ca.; Sep 28, 2025 at 02:32 PM.
i don’t think it’s regulator related but i had never known they had a CVR , my boss has a oscilloscope so im thinking about removing it and taking it to work and see if it’s working properly , another thought is maybe the floor high beam switch? do you happen to know if it’s rid into the the other lights? i didn’t see anything on the wiring diagram in the workshop manual
I was reading this as well as what others have wrote.
If your not putting out about 14V from the generator at about 1500-2500rpm measured at the battery, this "may" be a part of the problem. When my truck idles, the lights can be on the dim side, then rev it up and I have nice lights when the gen. kicks in. "Maybe" if your regulator for the gen. is cutting in and out, that "may" lead to flickering lights?
Just a thought,
Tom
I appreciate you responding Tom but i don’t think that’s my situation because i tried with the truck running around 2k rpm and same issue , was one of my first thoughts as well
A little off topic but related, a 67 car I have you can watch the ammeter swing while the turn signal is on. I believe it is an instant on then off situation that causes the alternator ( I know you have a generator) to produce a burst of energy following the sudden draw of the lights coming on and the frequency hits at just the right moment to cause an oscillation of sorts. I know my alt is charging borderline at idle as any increase in rpm reduces or eliminates the oscillation.
another thought is a bad contact in a switch or terminal. This can introduce a resistance and a cir that can handle 10 amps when it is clean, will have a large voltage drop due to the resistance of the bad contact. BUT it will only show up under load.
