My battery has been showing up weak-to-dead after a 25-30-mile cruise, keeping me from restarting after shutoff. So, I'm trying fault-isolate the issue.

I haven't checked the voltage regulator yet (don't know how), but I just finished putting my meter to the generator, in hopes of finding and answer. Here are my readings:

- Battery across the terminals (engine off): 13.68 volts (I keep it on a trickle charger when not driving for longer periods.)

- Generator (engine idling @ 900 rpm): Voltage across red and white terminals: 16+ steady; across red and gray/blue/purple (can't tell the true color) terminals: 7,8,9,10 cascading up, then back down from 10 to 7 then back up, etc.

- Revving engine: red to white: 16+ steady; across red to gray(?): 7,6,5,4 declining until revving stops, then it resumes the above up/down pattern.

Caveat: I know next to nothing about electrical issues. However, does this indicate worn generator brushes? If so, how do you access the brushes? (I once replaced brushes on a 1968 Plymouth Fury's alternator, so I think I know what they look like.)

Do these readings mean that the voltage regulator is okay?

I think my '58 has 27K original miles and this may be a replacement generator. Not sure about actual mileage or generator age, though.

Trivia: The generator is on the driver's side of the engine. I've never seen a '58 with that placement. All others I've seen are on the passenger side. Does anyone know why this might be?

Thank you, guys. I look forward to your wisdom.

Dave

 

Measuring across the battery with a trickle charger attached (engine OFF or ON) is not a valid test of anything... Measure across the battery terminals with engine OFF and no charger - should be like 12.4V or thereabouts. Measure the same way with engine running at fast idle...you should see 13.8V to 14.2V...no more than that...

Very simple "quick and dirty" check....if this shows something amiss there are further checks in the shop manual..

 

Frankie, sorry for the confusion. Obviously, I didn't measure the battery voltage with the charger on the battery. It was off. I just mentioned the charger for background information. As you mentioned, I did measure across the terminals with the engine off and no charger.

I haven't measured the battery with the engine running but I will do that. I'll also check the manual. Thanks for the help!

Dave

 

A fully charged battery that is nevertheless left on a charger can show a high surface charge of over 13 V, that dissipates in a short time.

What is alarming is your mention of 16V output from the gen. That indicates a grounded field, and likely a stuck regulator. Do not run it that way, 16v is about max output and the generator will not tolerate it for long nor will your battery, radio and light bulbs be happy about it.

The best test for a gen is to remove the field lead from the regulator and ground it while observing a DVM set to DC volts and connected across the battery. This will drive the gen to full out put, 15-16 V. If it doesn't, the gen ain't genn'in.

As mentioned above, racing the engine should produce 13.8 to 14.2 V, it all depends on battery state, ambient temp and load.

More likely is the regulator to be munged up. Just went through it with my 60 Electra. Took off the 2nd re-pop piece of crap and put on the original I took off 10 years ago because I thought it was overcharging.

I found a good selection of Delco NOS regulators, even though their were many different part numbers if it will work on a GM car from 56-62 it will work on your car. They are worth the money.

Dan

 

Dan, thanks very much for your keen insights. As I mentioned, I haven't investigated my voltage regulator yet. Maybe you can give me your opinion about what a savvy old mechanic mentioned to me the other day when I mentioned this problem to him.

He said an old trick is to give the regulator a firm rap with a larger screwdriver handle to see if that can "unstick" the relay. (I may be misquoting him some.) From my ignorant point of view, maybe the relay IS stuck and that's causing the generator to "back up" and overcharge. Then again, maybe I have no idea what I'm talking about (more likely).

Thanks again for your help.

Dave

 

The old 'tap' the regulator was an old trick to unstick points.
Just remember to raise the RPM to at least 1200 when doing all your testing as a generator will not put out enough of current to close the current cut-out relay in the regulator.
As stated 16v is way too high and should be somewhere near 14.0-14.5v when the battery is fully charged.
The voltage will be lower when the battery voltage is low and this is why all tests should be done with a fully charge battery.
The regulator I used on my two 61's is Standard Ignition VR22 and is still available, I sell them for approx. $42.00 in my store.
Joe

 

Indeed. Many of us are remiss in not mentioning this more often. Many an unnecessary battery or charging system part has been sold because diagnostics, especially load tests, were performed on discharged batteries. When a charging system problem is suspected the best first course is to slow charge the battery overnight and see that it took the charge by morning, and load test that battery. When good battery health has been established you move on to commanding full generator or alternator output by grounding the field at the regulator (on GM cars with "A" circuits). If the generator will go to full output with a grounded field you know the regulator or the wiring is at fault. 9 out of 10 times its the regulator. Back in the day these were considered consumable parts not unlike belts and hoses. They have a finite life span.

I recommend removing the field wire from the regulator and grounding it. This is because some who might use this procedure on other GM cars may have double contact regulators as used on A/C equipped cars in which grounding the field lug of the regulator while connected to the generator will immediately destroy the regulator.

As for banging on the regulator-this is only useful to point to a bad regulator. As with errant TV sets of yore banging on them is only a temporary fix.

The generator type regulator has three components with contacts. Two of them, the voltage and current regulators can stick and when either do the result is the overcharging you experience. The third is a cutout that opens when generator output falls below battery voltage to prevent the battery current from traveling backwards through the generator. Some original Delco regulators, most often the double contact variety were fused at the generator lug. But most are not. If that cutout should stick after you shut down the car and walk away often a fire is the result. For this reason I run battery disconnects on all my cars using generators.

You need a regulator. You can try the ones on sale at auto parts stores as mentioned above. My experience with them has not been good. The best option, in my opinion, is an NOS Delco regulator. There are many on eBay. Make sure you get a 12 V unit to work on a 56-62 GM car, but do not buy a "double contact" unit. These are identified by printed warnings (red or white print) on the cover never to ground the field terminal.

Danny Plotkin

 

Joe and Dan ... Thank you for your thoughts on this. I'm going to observe what you said and attempt to isolate the problem. I'm concerned about the steady, high voltage reading on my generator. I'll check the regulator next and see what's going on with that.

>>If that cutout should stick after you shut down the car and walk away often a fire is the result.<<

Dan, I do disconnect the battery after every run. Otherwise, I would be lying awake thinking, "Are my C1's wires melting?" Not conducive to sleep.

Thanks again, gentlemen.

Dave