Expert: Ernest (Ernie) Kenward - 10/13/2007

Question
QUESTION: Hi Ernie.
I have recently rebuilt a 1970 ford 4000 tractor , don't panic.
The wiring is the same as any 1940-60's car. comprising 12v bat and dynamo with regulator.
I have replaced every elec component except the battery. Though old just holds its charge.
But the problem is the system does not re charge the battery!!! The meter only shows the original battery charge and does not increase / decrease with the throttle movement.

The dynamo has been polarized and shows a   charge when running , against my volt meter and varies with a rev change.Iam at a loss to now what to try next, any ideas.
Martin


ANSWER: Well, I would admit that my tractor experience in the main comes down to taking in and greatly enjoying the annual antique tractor pull at the Agassix Corn Festival. I am into "Heavy-Haul" in its locomotive context and so get a kick out of the torque*speed=power equation in all its forms.  I shall give this a try ...

A big problem with old flooded-type (lead-acid liquid) batteries is that, as they age, they eventually evolve into something that more resembles a load bank than a battery.  Sulphation does that.  Lead-acid batteries sulphate over time to a small extent even under normal maintenance, and the sulphation becomes pronounced if the unit is allowed to sit fully discharged for a period of time.  

There is little point in keeping an ancient battery on a job it cannot do.  However, if you are a purist (understood!) who wants to maintain the period appearance of the tractor, you might be able to find a battery manufacturer/rebuilder who might be able to provide a lead plate system that will fit your (presumably now obsolete) battery case and thus refurbish it for you.  The reliability and performance for the dollars spent would not be up to that of a current battery however.  Such is the cost of keeping true to history!

As to your charging system, I wonder whether the voltage regulator is functioning (or even present!).  A voltage that varies with RPM suggests that the field is being maintained at a constant level, rather than being allowed to vary as needed to adjust the generator field to maintain the 13.8 to 14.2 VDC running voltage.  Excess voltage, as would result at higher engine RPM or light load on an unregulated generator would result in battery gassing, loss of electrolyte, and sulphation.  Is it likely that someone might have, in the need to get a job finished, taken the expedient work-around of simply tying the generator output back to its field terminal?  It might be time to get that regulator going again.  Even if you can't replace it, the chances are that you can make it work again.  

Even as late as 1970, there were many regulators that relied on magnetic coils and interrupting contacts.  Usually, the only problem is pitted contacts.  Cleaning these, filing off the pits (carefully, as you don't want to remove more finish of the good surfaces than you can avoid) and coating them with electrical contact and terminal grease will probably return to you a working regulator.

You may need to adjust it, if the loaded output voltage from the generator is stable, but much above or below 13.8 to 14.2 (max) volts.  This can be done by carefully adjusting the tension by bending the bendable-metal springs that hold the VR contact against the force of the VR coil until the voltage is in the correct range.  The current-limit coil, if equipped, may similarly need adjustment.  One caveat: don't do either adjustment unless you have the evidence given by proper instrumentation that there is a problem!  Avoid the impulse to tweak!  (I always have to!)    

Now, I recognise your apparent desire to keep things original, but consider the following ...

My 1959 Edsel originally had a group 29 battery, now long off the books, and just as well; this was a much undersized battery, even for the relatively light electrical loads of the time.   There was plenty of room at the battery shelf in the engine compartment to mount a modern group 24 tray, and thereby update to modern lead-acid and, better yet, sealed maintenance-free batteries.  Did I chuck the original group 29 tray?  No ... I sandblasted and refinished it, painting it the original gloss black but using epoxy paint, and then put it away for possible reinstallation later should I or a successor eventually want to restore the car to OEM specs and equipment.  

I did the same with the old stationary-field generator (or dynamo, as you correctly termed this DC generator) and regulator, as I modernised the system in 1988 to use the common Ford 65A alternator.  I maintained the appearance of the OEM regulator at least by designing and fabricating a circuit board to fit the regulator case, but using a 338 voltage regulator IC and supporting electronics.  

I was able to upgrade the ignition system as well, to use the electronic modulators used by Ford in the seventies and eighties.  One of the good points about the FE engines used in the late-fifties Fords was that the series evolved into the seventies, and made it possible to get a replacement distributor that, while externally identical to the original, was equipped with the magnetic pickup needed with the modulator rather than points.  As a result, the system appears identical to the original (the modulator being hidden) while providing all the performance and plug life of the later system.

My original distributor and a couple of regulators were put away, after being tested, serviced as required, and refinished.

My own fun experience is with cars, RVs, railway passenger equipment, locomotives, and industrial and commercial systems.  While I have not had the pleasure of hands-on work with tractors, I gain my own confidence from the fact that most systems share a commonality of basic principles, along with the distinctions brought about by their unique applications.  One does one's homework.  Good technical troubleshooting, as does the practice of any good engineering comes down to that.

Good luck with this project ... EGK

---------- FOLLOW-UP ----------

QUESTION: HI ERNIE
Many thanks for your prompt and extensive reply to the tractor  /battery not charging problem.

Having tried out what you had said and many other ideas i still could not get things to work though all parts were new except the battery"!
after several months of desperation i took the REGULATOR back to the supplier and they changed it for another.
(IT WAS A COPY OF THE LUCAS ORIGINAL)
THOUGH IT WAS OUT OF WARRANTY.
And guess what YES THAT WAS THE PROBLEM ALL THE TIME
EVERY THING NOW WORKS AS IT SHOULD !!!??!
MANY THANKS
MARTIN  

Answer
Glad to hear that all is working properly!  All too often, it is the component we set aside, taking for granted that it is not the problem, that turns out to be the key all along.

The reference to Lucas reminds me of (i) the experiences over the years of several friends who have had the pleasure of driving and maintaining Austins and other English cars, and (ii) a tongue-in-cheek story of the "Philogiston principle", a story I often pass along to my engineering students.  Unfortunately, this mode is not set up for attachments, and the story is a pdf document and so I cannot simply copy the text of it via a "control-C" to include it in a reply.  If you would like a copy, get my e-mail alias from the BCIT web site and send me a memo, and I will be happy to reply it to you.

I have been making good headway with my vehicle projects as well, and have just about completed my third program of electrical and PLC-control upgrades on my E250 motorhome conversion.   A tough-built truck is easy to upgrade and also rebuild like new again every few years, although increasing gas prices are now making me think about diesel swap options.  In the time being, my diesel car is saving me lots!

Nice hearing from you again!

Cheers ... EGK