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Discussion Starter · #1 ·
1970 standard

1) no dash lights >>> replaced headlight switch >>>> FIXED!!!
2)not satisfied with stock brightness so i swapped for hi po LED kit. Also replaced cluster voltage regulator (low fuel and coolant temp readings FIXED!!!)
3) connected cluster to test LEDs (without car running) WORKING

BUT WITH THE CAR RUNNING

1 of the 5 backlight LEDs (middle) cuts in and out when it feels like it.
Under engine load/accelerating all interior lights flicker rapidly and then work normally at constant load/speed

This is all lights... guage/AC control/passenger courtesy. I even turned on the floor interior lights. they all flicker together.

This could have always been an issue. I think the incandescents are not as noticeable as they have an afterglow, but after seeing the LED's rapid cutoff, I know notice the incandescents as well.
 

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Discussion Starter · #2 ·
After researching a bit... I'm thinking of replacing the main voltage regulator in the engine bay. Gonna see if i can clean up some grounds as well in the battery/ALT/regulator department.

If anyone has any other suggestions, it would help me out a lot. I can already hear my buddies making fun of me.
 

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There is a constant voltage regulator under the dash that may be causing the blinking. You will need to go to a solid state one rather than the factory one. BOB AKA 1969XR7Vert makes them as one source to go to. LED lights use much less current than standard bulbs for one which the constant pulsing of an old school regulator would show up
 

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Discussion Starter · #6 ·
I replaced the original with the one from WCCC. I'm guessing that one is not solid state? Also, i thought the back lights do not go through the VR... just the instruments.
 

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I would also test the alternator for for a bad output diode. If you have a shorted diode in the rectifier, you will induct an AC waveform component into the output DC and can cause a flicker. A quick check is to measure the alternator output voltage using a decent voltmeter in the DC Voltage mode and then do the same measurement with the meter set in the AC voltage mode. The AC voltage reading should be very low---been so long I don't remember the numbers anymore, but if you get any AC voltage, the specs for acceptable levels should be available.
 

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Discussion Starter · #8 · (Edited)
There is a constant voltage regulator under the dash that may be causing the blinking. You will need to go to a solid state one rather than the factory one. BOB AKA 1969XR7Vert makes them as one source to go to. LED lights use much less current than standard bulbs for one which the constant pulsing of an old school regulator would show up


just checked the 70 wiring diagram. Cluster Voltage Regulator only goes through my fuel/coolant gauge. Both working better than ever. Good idea to rule that out though
 

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Discussion Starter · #9 · (Edited)
I would also test the alternator for for a bad output diode. If you have a shorted diode in the rectifier, you will induct an AC waveform component into the output DC and can cause a flicker. A quick check is to measure the alternator output voltage using a decent voltmeter in the DC Voltage mode and then do the same measurement with the meter set in the AC voltage mode. The AC voltage reading should be very low---been so long I don't remember the numbers anymore, but if you get any AC voltage, the specs for acceptable levels should be available.


This makes since. How do i safely put a meter on the alternator with the car running? Kinda of a dumb question i know.
 

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Yeah - your right......I was thinking it was all of the stuff, but just realized light bulbs would have needed more than 5V to go! LOL SO much for that theory. Something must be making loose contact soemhow when it's running......?
 

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This makes since. How do i safely put a meter on the alternator with the car running? Kinda of a dumb question i know.
The most accurate way is to test the voltage at the alternator output terminal. Since this is hard to get to when spinning, check the voltage at the battery side terminal of the starter solenoid. Measure using the meter positive lead to the terminal and meter negative lead to a good ground--preferably the battery neg post. Note the readings at idle and at about 3000 RPM. Should be about 14 volts with the motor at 3000 RPM and no loads. To check for a shorted diode, set the meter to measure AC voltage (typically 20 volt range) and repeat the prior electrical connection steps. Change the meter range to a lower range as needed to get a good reading. A good alternator should should have below 1 volt AC on the output. Turn on all the headlights and recheck the AC measurement again. I also wouldn't rule out the voltage regulator under the hood and also check cable connections at the battery terminals and at the regulator connector also the wire harness feed from the alternator. My regulator connector was corroded and was causing issues. Don't forget to check for a good engine ground.
 

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Discussion Starter · #12 ·
The most accurate way is to test the voltage at the alternator output terminal. Since this is hard to get to when spinning, check the voltage at the battery side terminal of the starter solenoid. Measure using the meter positive lead to the terminal and meter negative lead to a good ground--preferably the battery neg post. Note the readings at idle and at about 3000 RPM. Should be about 14 volts with the motor at 3000 RPM and no loads. To check for a shorted diode, set the meter to measure AC voltage (typically 20 volt range) and repeat the prior electrical connection steps. Change the meter range to a lower range as needed to get a good reading. A good alternator should should have below 1 volt AC on the output. Turn on all the headlights and recheck the AC measurement again. I also wouldn't rule out the voltage regulator under the hood and also check cable connections at the battery terminals and at the regulator connector also the wire harness feed from the alternator. My regulator connector was corroded and was causing issues. Don't forget to check for a good engine ground.
VERY VERY VERY helpful. I will be following all of these tips/steps. I've been thinking about switching over to a 140amp 1 wire anyways. So i'm kind of hoping i get some bad readings :)
 

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Discussion Starter · #13 ·
UPDATE

Replaced stock alternator with a powermaster 1 wire (wanted to do this anyways so i can get a powerful stereo). Replaced old battery as well. I am now getting 12.4 DC volts (engine off), and 14.8 @idle. No more surging of the lights with higher rpms. Great clean looking upgrade.

However, I am still getting flickering lights. (headlights, gauge lights, interior lights) The light that i find the most interesting is the courtesy light. It is not wired through the headlight switch... so i can rule that out i'm sure. They all flicker in syncro.

1. at idle (no flicker)
2. accelerating/constant speed (flicker)
3. deccelerating (no flicker.. rock solid)
 

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Discussion Starter · #14 ·
Another thing that i have noticed that may be of interest...

When the flickering is happening while accelerating/cuise.... The turn signals (solid state) flash faster. when deccelerating... they return to a normal interval
 

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sounds like it's either not regulating very smoothly or there is more draw than the flasher can keep up with. On my truck I had to put in a heavey duty flasher to make up the diff when I put on a trailer......it acted the same way until I did that
 

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Discussion Starter · #16 ·
sounds like it's either not regulating very smoothly or there is more draw than the flasher can keep up with. On my truck I had to put in a heavey duty flasher to make up the diff when I put on a trailer......it acted the same way until I did that

I will definately try disconnecting my turn signal flasher to see. So strange... Doesn't matter if it is 10mph (low rpm) or 60mph (higher rpms). If it is contant or accelrating = flickering.. deccelrating = completely normal. The entire electrical system seems to be affected.
 

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You might want to check your main grounds. I would also check your spark plug wires to make sure the insulation is not cracked.
 

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Discussion Starter · #18 ·
You might want to check your main grounds. I would also check your spark plug wires to make sure the insulation is not cracked.
i replaced Battery - to engine ground cable. I also wire brushed the connection point. I will check spark plug wires tonight. ty sir
 

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Battery ground to engine ..... engine grounds to firewall .... firewall/body grounds to frame .... remove, clean,inspect and reinstall all of them to start with ....
 
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