Electrical Woes

[Bill Dally]

I recently relocated my 1964 356 SC from my old house in Los Altos Hills, CA (Bay Area) to my new house in Incline Village NV - about 250 miles, mostly on I-80. When I stopped for gas in Dixon, CA - about half way - the car wouldn't start. The battery clearly had not been charging. I push started it and continued on my way. A little while later the generator light came on - with an odd behavior that it would be off at low RPM (idle) but come on brightly at cruising RPM (3500 - 4000). At this point I hoped I would make it to within 100 miles of home so I could get an AAA tow. With the headlights on, I wasn't sure how long the battery would last. I continued driving, with the headlights seeming somewhat dimmer than normal (wish this car had a voltmeter and ammeter in the dash) the generator light was on steadily but things were stable. When I reached King's Beach - almost home - the generator light went out. I made it home, put the car in the garage, and established that the battery was completely dead.

This trip was made right after flying back from East Africa - a 30+ hour journey, so maybe it was a good thing that I had this issue to keep me worried enough to stay awake and alert - much more effective than a cup of coffee.

The next morning I ran some tests and found (a) the generator bulb in the combination instrument had burned out - things had not magically healed at Kings Beach. I also disconnected the B+ lead from the generator, ran the engine at 2,000 RPM, grounded the DF lead, and measured about 4V at D+. So, the generator is bad. I also measured the resistance from DF to D+ to be about 2 ohms. I pulled a brush out and found it to be about 0.49" long and the commutator was showing noticeable wear from the brushes. I also noticed that there are condensers mounted to both the D+ and B+ leads on my voltage regulator. These are not shown in the wiring diagram I have.

Its interesting that the car ran just fine for almost four hours running on about 4V - albeit with the headlights a little dim. That's the beauty of a simple mechanical ignition. Any car with electronic ignition or fuel injection would have died long before the voltage got that low.

Some questions. First, what is the minimum length for the brushes. The slide deck on the website says they are 0.75" new. How much wear is allowable. Would new brushes fix my problem, or do I need to completely rebuild the generator (probably not a bad idea in any case). Second, any suggestions on where to get a rebuilt generator (or have a rebuild done). I'm assuming I can't go to the local NAPA store and find one on the shelf. Third, I can't help wondering if the root of my problem isn't the wacky mechanical regulator. Has anyone designed a solid state replacement for this antiquated contraption? A couple 20V power MOSFETs controlled by a simple voltage and current sensing circuit would be much more reliable.

[Doug McDonnell]

http://www.abcpartswerks.com Owned by Doug Darrah Registry member but maybe now run by his kids.Phone number on website is for Doug in Bonita Springs,Fl but shop is still Wisconsin. They advertise in the magazine or Zims for rebuilt. The condensers are common on the VR They are for electrical noise suppression. PS If day light you can drive all day on a fully charged battery as long as you leave your headlights off. I am assuming you still run 6 Volts.

[David Jones]

Bill and others who may run into this problem. The reason the generator light came on brighter as the revs climbed is because the battery fed more and more current back to the generator field trying to increase the output. The usual reason for this is the brushes and a new set of brushes will often cure the problem. Bill makes a good point about the battery lasting a good long while when the generator fails, but the thing to remember is to run as few electrical loads as possible including bump starting whenever you can. If there is a slope park on the high point. The 356 will roll a lot easier than most cars. When I was younger and did not have any disposable income I once went a month without a decent battery by using the hill start method. My battery would always work for about 4 hours after a charge but overnight it was sure to fail.
It really does not matter what ignition system you have except for maybe a Pertronix which has a definite fail point at about 5.2 volts. They all require the same amount of power to run which is about 6 amps at 4K rpm. I carry a small 6 volt 7 amp SLA battery in my glove compartment which will run the ignition for about an hour plus in fully charged condition. It is also useful when trouble shooting.
I just had a similar issue with my 59 coupe when I noticed it took longer and longer to show a full charge on the charger even after a 1 hour drive. When I checked the generator it was showing a 10 amp discharge at 3K rpm. A new set of brushes cured the problem.

[Greg Bryan]

Bill - There is no updated electronic voltage regulator for the 6 volt system that I'm aware of, but Bosch does make a fully electronic 12v voltage regulator.
P.S. Cheers from South Lake Tahoe! - we need to start a Lake Tahoe 356 get-together.

[Alan Hall]

There seems to be a lot of car events at Tahoe, usually one marque holidays at one of the So. Lake Tahoe casino hotels. There is an MG "gathering of the flock" event going on this week based at the Hard Rock hotel/casino. Bill- good luck sorting out the generator issue, glad you did not get stranded! As Harry Pellow used to say, 356's are very good at getting you home before they give out.

[Brad Ripley]

Bill and Greg -- off the topic of generators -- but no need for a Lake Tahoe 356 group -- we already have a Reno 356 Group only 35 miles over the hill from The Lake. Next breakfast is this Sat, 9 AM at Napa-Sonoma South, 7671 South Virginia Street. Usually 20-25 356ers every third Sat of the month.

[Al Zim]

We have two 6 volt restored generators on the shelf. Each generator gets a new armature, new bearings, new field coils, and side plates that hold the bearings when they are worn out from the vibration as the armature turns. Each generator comes with a warranty. The casing on the generator is plated and the outer housing is lightly finished. The generator is very presentable but probably should not be use for serious concurs vehicles. Zim's is still able to obtain 6 volt regulators new but we feel that soon they will be impossible to find. REMOVE THE COVER ON YOUR REGULATOR and look at the points. If they are not smoothly finished time for a new regulator. Make a careful check on your pulley halves to check for wear on the center and where the screwdriver holds the pulley. Pester our parts guy to throw in our special generator screwdriver in the deal, tell them al said it was OK. The price on the generator is $465.00 with a core of $250.00. 800.356.2964 al zim 2018/09/12 Call me if you have questions.

[Greg Bryan]

Brad - thanks for the meeting info - I'll be sure to attend next spring when I'm back at the lake.
Bill - did you sort out your generator issue?

[Bill Dally]

Brad - thanks for the meeting info - I'll be sure to attend next spring when I'm back at the lake.
Bill - did you sort out your generator issue?

Yes. I found a place in Van Nuys that sold me a rebuilt generator outright (no core charge) for $300 - new bearings, commutator turned and undercut, new brushes. I'm going to find someone with a lathe to turn the commutator on my old generator and then reassemble it with new bearings and new brushes and keep it as a spare - although this is not a field replaceable spare, it was a pain to swap generators - oil filler, post with SN, and oil filter all had to be removed to get the fan out of the shroud.

I drove it over the Mt Rose Highway to Reno and back earlier this week and had no electrical problems. The oil temp was getting a bit hot on the way back. I had to slow down a bit.

I'll try to make it to one of the Reno 356 breakfasts one of these days.

[Steve Hatfield]

Bill Dally,
Please email me your replacement gen source details.
TIA
Steve

[Charles H Jacobus]

My generator runs ~7.6 volts with no load at 4,000 RPM. Is that too high? Type regulator in use shown below.

Chuck

[Paul Lima]

I'd say that is slightly on the high side; ideal is about 2.4v per cell/7.2v for a 6v battery. The regulator can be adjusted this small amount. I'd watch the water/acid level in the battery. This slightly high voltage may be ok, but it may cause your battery to run warm and lose water more rapidly.

[Dick Weiss]

If the brushes (@ least the top one easily seen) is even or a little below the top/end of its holder, it's time for replacement. The bottom brush will be difficult along w/the tight screw connection on the lead, but w/dexterity--and a mirror to R & R in reversed image, it can be done w/o generator removal.
Blow out the dust w/an air gun unless the commutator looks dark from age-wear and needs a refinish.

The tricky part is pulling out the brush spring-tip (w/a wire hook) sideways just enough to allow removal--
and NOT 'popping' off or breaking it. I've done a few replacements over the years successfully--one of which was done in the parking lot during an ECH in Williamsburg, VA.


CAUTION: Don't drop the top screw into the generator's end--a magnetic screwdriver will retain it along w/its washer; Ditto w/the bottom screw or use a short screwdriver having a retainer clips or split-blade end.

[Charles H Jacobus]

I'd say that is slightly on the high side; ideal is about 2.4v per cell/7.2v for a 6v battery. The regulator can be adjusted this small amount. I'd watch the water/acid level in the battery. This slightly high voltage may be ok, but it may cause your battery to run warm and lose water more rapidly.

The reason I was a little concerned at 7.6 was because it's a gel cel Optima. Thanks for the schematic, Paul. I'll pull the cover and see if I can figure the adjustment out.

Chuck

[WilliamVaughan]

regarding " I'll pull the cover and see if I can figure the adjustment out."

Watch it in operation.
Resist the temptation to push any relay armatures while the regulator is in the car and the battery is still connected.
Photograph it and its connections. Disconnect the battery. Take the regulator out. Open it up. Study it. Become intimately familiar with all three relays.
Consider biasing the voltage sensing relay with light finger pressure while the engine is running at 3K RPM while watching a voltmeter.
Then start thinking about making the adjustment.