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Discussion Starter · #1 ·
Yes, so i've had that before with other old cars but never really looked into it. At dark, when engine is on at idle, both the dash lights and the headlights flicker. If I race the engine, the flickering intensifies. What is it and should I be alarmed?

Thanks!
 

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Rosko said:
Yes, so i've had that before with other old cars but never really looked into it. At dark, when engine is on at idle, both the dash lights and the headlights flicker. If I race the engine, the flickering intensifies. What is it and should I be alarmed?

Thanks!
That sounds very much like a problem with the voltage regulator unit at the back of the alternator. It's possibly just worn brushes and not a defective voltage regulator itself, but you can check what the voltage reg is doing by measuring the voltage at the battery terminals when the engine is running.

With the voltage regulator 'enabled' (charging light in the dash above the left-hand gauge off), you should measure between 13.5 and 14.5 volts at the battery terminals, and if you get a helper to move the throttle plate by pushing back on the spring holding it in the idle position on the side of the throttle valve, check that the voltage doesn't go outside that range.

When you turn the engine off, what is the terminal voltage on the battery? Does it decay quickly below 12.5 volts or stay around the 12.5 to 13.5 volt range? I've seen one instance where an almost new battery developed a 'collapsed cell' (basically one cell of the lead-acid battery was short circuited) and the battery would never retain any charge. The result would be that the charging circuit worked fine, but the regulator output was quite erratic (though not much off the correct range), but the battery voltage fell down to about 10 volts almost immediately.

The other possibility is that the alternator itself may had a defective diode and it might be resulting in the voltage regulator not being able to produce a 'flat' DC output. That's a lot less likely than a problem with the voltage reg (or it's brushes) though.

Craig.
 

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What was it finally?

I'm having the same problem, but it only flickers when the engine is running.

Am I right to assume that it should be related to the alternator/voltage regulator since everything is normal when the engine isn't running?

I'll have that checked next Monday by my mechanic since I need to get my Winter tires installed.
 

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Discussion Starter · #4 ·
It was the voltage regulator and it's pretty simple to install a new one yourself. It is also cheap - $10-12. The brushes wear off, but you replace the whole voltage regulator. Screws on the back of the alternator, 2 screws, one of which is hardly accessible though. Fitting the brushes in place is also a bit tricky, but if you are patient and stubborn you will get it right.
 
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