How do I know if I have a bad voltage regulator in my 57 olds. My generator light comes on and off intermittently

 

You have not stated at what speed this anomaly occurs with regards to the GEN light. If the engine is idling, a flickering GEN light doesn’t necessarily mean generator or battery trouble UNLESS the light remains on after the engine speed has been increased. This is the case with my ’57 Ford; this verbiage is taken from the owner’s manual.

 

I’m from a later era Olds, 1966, but will volunteer a couple of things about voltage regulators.

If you have the factory _generator_ & a voltage regulator, everything below may be wrong/irrelevant.

1) The voltage regulator, at least in the mid-60’s, used points to more or less throw away or short the output from the alternator if the system voltage got too high, or if the battery was fully charged. I upgraded my ‘66’s (originally voltage regulator equipped) to internally regulated alternators using the diagram Joe P posted here a long time ago.

2) After many years of use, voltage regulator points can get burned / carboned up / etc which may be affecting your charging system, especially at low RPM’s. All those decades ago, I believe voltage regulators were a service part - expected to be periodically replaced like an oil filter, but at much longer intervals. But as these vintage cars aged into the junkyards, this knowledge may have been forgotten. Also replacements may have gotten harder to find. If you can find a NOS or replacement voltage regulator, that’s a quick (and maybe inexpensive) fix.

3) At the edge of this problem, someone may have built a solid-state or digital voltage regulator retrofit part. It can be built. I just don’t know if it has been. Dig around under the other GM brands from your year/era and see if someone has built something that might work. But don’t just bolt in a Chevy or Buick piece just because it fits. The wiring pin out for those brands may be different from your Olds and could be bad (or very bad) for your car’s electrical system.

My 1st move would be to remove your existing regulator from the car, and use a mild abrasive like 600 to 800 grit sandpaper to file off any carbon burning your original regulator points may have suffered. At least in my ‘66’s, as designed, this was a simple bench operation. About 10 seconds to disconnect the 4 pin connector from the regulator, another 60 seconds to pull the regulator off the firewall. Plus a minute or 3 to open the casing to get a good look at the points & solenoids inside.

My 2nd move would be to confirm the gap size between the points mating surfaces are at factory specifications. You’ll need a feeler gauge. If the gaps are too large, in my years the fix was the bend the arms toward each other just a tick to get them into spec. If the gaps are too small, you do the reverse, you bend the points arms away from each other just a tick. Your chassis service Manual or others here may have the voltage regulator gaps you’re shooting for.

If you like the stock system, keep it. It’s correct and well known, provided that it works correctly. Just know that with a few modifications you can upgrade your charging system to somewhere around 1975 technology with an internally regulated alternator, totally eliminating the voltage regulator as a component. In your year, this may also mean a conversion from generator to alternator. I can confirm the later regulatorless-system, after some wiring changes available here, work better than what Olds had in 1966.

I freely admit your car is a generation or 2 before the ones I know. Just offering what little I know in the case that it helps you.

Cheers
Chris

 

I had one of these built. Here is the reverse engineering drawing from what I received, been running it for over a year now, perfect. https://www.dropbox.com/scl/fi/simed...=zaq6bjmm&dl=0

 

If you decide to replace the voltage regulator, remember, the new one--old style, must be polarized. It's easy, and the procedure is in the maintenance manual.

 

Perhaps I'm nit-picking, but you don't polarize the VR, you polarize the ALT via the VR. ALT needs to know which direction to send the voltage.

 

Perhaps I'm being a bit nit picky. It's a generator. And you do it at the voltage regulator. Just kidding, but you get the idea.

 

Spot on correct, Sir.

 

The generator light will flash on if the idle speed is too low.
This is normal.

What is the voltage at the battery when the engine runs at 1500 RPM with the headlights on?
It should be between 13.5 volts to 14.5 volts.