News:

Due to a technical issue, some recently uploaded pictures have been lost. We are investigating why this happened but the issue has been resolved so that future uploads should be safe.  You can also Modify your post (MORE...) and re-upload the pictures in your post.

Main Menu

1958: Generator Light stays on...

Started by Caddy58, July 22, 2014, 10:52:15 AM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

Caddy58

I need help identifying a problem on my 1958 Sedan de Ville.
Admittedly I am a little "electronically" challenged, but in the last 17 years my car has never given me electric problems; well, until yesterday...

We did a short cruise (about 8 miles), parked the car for about an hour and when we started it again the "Generator Indicator" light stayed on. We drove back home, hitting 60 mph at times, but the light was still on.

I measured the voltage at the Battery:
Engine Off:  12.39 Volts
Engine at slow idle, 12.18
Engine at running speed:12.20

So it appears the generator / regulator are not charging the battery. I have cleaned the contacts in the regulator, but no change.

I have an A/C car, so it uses a "Double Contact Regulator". I also have the 1957 and 58 Shop Manuals, but I find them more confusing then helpful as they do not specify how I can measure voltage at the generator.

Questions:
How do I best identify if it is a generator or a regulator issue?
How do I measure the output of the generator?
Which contacts do I need to measure? Generator "A" to ground?


Any help is much appreciated
Cheers
Dirk Warwel
Driving a 1958 Cadillac Sedan de Ville in Germany

Dave Burke

Hi Dirk,

As the owner of a '57 with some electrical issues (well, former ones), I'll pitch in.  Yeah, it's a pain in the tuchus.  First, take a look at your regulator.  When you run the car, does it get warm?  Same question for the generator.  Take the cover off of the regulator - do the contact points look oxidized or burned?  I have gone through both single and double-contact regulators and favor the latter.  Of course the doubles are about 3 times the cost of the singles.  Anyway, after looking at them, if it looks burned, it probably needs to be replaced.

Between the battery and the regulator should be a wire that is actually a fusible link.  Is it solid?  If it has burned through, the generator cannot charge the battery.  As to measuring the output of the generator, I use a multi-meter and connect the positive lead to the "Bat" terminal (NOT the field terminal) and the ground to ground - but what you really want to check out is the amperage.  I suggest that you contact the local automobile starter and generator repair places nearby - they should be able to test it for you.  I did that recently in Auburn, AL and the guy even did it for free.  I had reason to suspect the generator because I had recently rebuilt it myself, and there are usually few problems greater than those I cook up for myself!

Finally, I broke my own rule about not drilling any holes in the car (to be fair, the previous owner had done some, so I didn't feel as bad as I might) and mounted a voltmeter in the car.  It runs off the accessory circuit and generally hovers between 12 and 14.8 volts - right where it should be.  Of course, my car is a driver and if you are doing a real resto, you will certainly want to do something else.

Good luck - believe me, those electrical bugaboos are for the birds!

Dave Burke
1957 Sedan Deville
1963 Series 62 - Project LUX
1983 Maserati Quattroporte

"Who loves ya, Baby?" - Kojak

Caddy58

Hello Dave,

many thanks for the hints.

I have checked the wires, they look all solid
I have checked and cleaned all connectors
The regulator looks surprisingly good inside: No burn-marks, deposits or crud. I had previously cleaned the contacts in the regulator.

To measure the voltage of the generator I disconnected the "Field" at the regulator and measured between the Generator Battery terminal (not marked on my generator, but the other terminal is clearly marked "F") and ground: I got 0.1 Volt.

I conclude that the generator is "kaputt". Does that seem like a plausible conclusion?

Many thanks
Dirk
Driving a 1958 Cadillac Sedan de Ville in Germany

dplotkin

Dirk:
A non-functioning charging system needs to be diagnosed as per the shop manual. Looking at a regulators contacts or feeling its cover or the generator for heat will tell you little that is valuable. You have already established it is not charging.

1. Cleaning regulator contacts with anything other than crocus cloth or a dollar bill is a mistake.
2. A generator can be momentarily full fielded by jumping field and batt terminals on the regulator while watching the voltmeter you have connected to the battery. While jumped the voltage should rise significantly if the generator is working. This test must be very brief and you should not perform it if you are unsure of yourself.
3. Generators use carbon brushes to conduct its full output from the armature's commutator. That is their weakness over the alternator that replaced it. If the generator has failed it will likely be because of open field coils or worn brushes, both easy and quick fixes. The regulator is even easier.

My best advise, since you admit to being a novice in this area is to take the car to a automotive electrical shop which most cities have. He can test both and if necessary refurbish your generator with new brushes, field coil if necessary, and a cleanup of the commutator.

Dan
56 Fleetwood Sixty Special (Starlight silver over Dawn Grey)
60 Buick Electra six window
60 Chrysler 300 F Coupe
61 Plymouth Savoy Ram Inducted 413 Superstock
62 Pontiac Bonneville Vista
63 Chevy Impala convertable
63 Ford Galaxie XL fastback
65 Corvette convertable 396
68 Chrysler New Yorker

Caddy58

Hello Dan,

many thanks for the additional feedback.

1. I have cleaned the contacts with a 800 grit emory paper, specifically designed for copper contacts. Though it is a little more abrasive than a dollar bill it will typically do a very good job cleaning contacts without scratching them.

2a. I have followed the guidance in the 1958 shop manual and disconnected the Field terminal at the regulator. I have measured the generator battery terminal and got 0.12 to 0.17 volts, the engine running at 1500 to 1800 RPMs (well, educated guess)

2b. After a call with my Garage (specializing in old Cadillacs and Jaguars, but unfortunately100 Miles away) I have grounded the generators field terminal whilst performing the test 2a. The voltage at the generator battery terminal only increased to 0.22.

3. So based on these tests we concluded that it is most likely to be a failure of the generator. The order for a generator overhaul kit is going out, but the overhaul will be done by my garage (that would be waaayyyyy over my head....)


Cheers
Dirk
Driving a 1958 Cadillac Sedan de Ville in Germany

bcroe

Mine was always the brushes; I'd check them before anything else.  Bruce Roe

Dave Burke

Brushes are cheap and easy to install too.

Dave
1957 Sedan Deville
1963 Series 62 - Project LUX
1983 Maserati Quattroporte

"Who loves ya, Baby?" - Kojak

Caddy58

I am not sure about the "easy to install". I think it would not be easy for me... :-)
But I am sure my garage can handle it.

Many thanks for the advice and help!
Cheers
Dirk
Driving a 1958 Cadillac Sedan de Ville in Germany

Walter Youshock

I'd check the regulator.  I had a similar problem with the '57 and I readjusted the regulator with the correct ammeter.  The dash light never glows and there's barely a drain with all lights and radio on.  An old mechanic buddy of my dad said most of the time it was the regulator, not the generator.  And DELCO regulators were the best on the market.  If you buy a replacement regulator, it needs to be adjusted on the car.  You can't hook it up out of the box.  It's like a carburetor for your electrical system.

A regulator is a series of contacts that are on/off; off/on constantly.  The generator will supply power as it turns.  The regulator is the "brain" that controls what goes back into the battery.  Too much current and you'll fry the battery.  Too little and you'll drain it.

CLC #11959 (Life)
1957 Coupe deVille
1991 Brougham