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Thursday, January 27, 2011

Alternators, Models and Design, Part 2, Delco 10SI

Next in the Delco series is probably the most popular alternator of all time, the Delco 10 SI.  This alternator was the simplest in design, easiest and cheapest to repair and very versatile in it's applications.  GM started using this unit in all their vehicles in about 1972 and has been widely used in all sorts of vehicles, trucks, tractors both agricultural and industrial, and marine applications, up until the early 80's.  This unit is still in wide use today and is being rebuilt and/or reproduced even now.  I've built or rebuilt and sold a lot of these units myself, over the years!


Lots of you might recognize this unit, as the one they built a lot of 'one wire' units out of.  Many have used this unit as a replacement for equipment with bad wiring, on street rods, replacing generators on both vehicles and tractors, or any application that doesn't have all the proper wiring to operate wired units.  It's great for people who don't understand wiring and need something simple to hook up.  All that is needed is a wire connected to the battery post on the back of the alternator to the positive post on the battery.  That's it!  It's just that simple!  The unit grounds through the case, so if external grounding is necessary, there is a threaded hole in the back for a bolted connection.  I have never seen an isolated ground on this unit but that doesn't mean one hasn't been produced!

Converting one of these units to a one wire application is fairly simple, but sometimes not easy.  The only component that needs to be changed to make it a one wire, is the regulator.  The problems you can encounter is the properties of the stator and rotor.  There must be a tight clearance between these two components or it will have trouble self starting.  Another factor is the ability for the rotor to hold residual magnetism.  Some alternators will still work with poorer components, but you have to race the engine up to get it to energize.  In my experience, it's about a 50-50 shot, that changing the regulator will make one work as a one wire unit, without changing other components!  Usually if the unit is a one wire, there will be a black rubber plug capping off the two spade terminals. leaving only the post to hook the battery wire to.


In most applications, the terminal connections are easy to identify and are always the same.  The only exception is if the unit is built for an external regulator, which I will cover in the next post on variations.  The 'BAT' or battery terminal is of course the insulated post.  The two spade or regulator terminals are as follows, the number 1 terminal is the exciting and indicator light terminal.  This terminal must be connected to a switched source, meaning hot when the key is on and dead when the key is off.  It generally is also connected through an indicator light (or dummy light as it has been called), or usually some sort of resistor needs to be inline with this terminal.  It should not receive a full 12 volts as it was not designed that way.  The light bulb serves as a resistor which is inline with this terminal so sometimes if the bulb is burned out, the alternator won't charge!

Warning; If you connect this wire to the ignition coil, the alternator will feed back into the coil and you won't be able to turn off the vehicle, without grounding out this terminal or unplugging the harness plug from the alternator!

The number 2 terminal is a battery sense terminal, which senses the amount of charge that's in the battery and tells the alternator whether to charge more or less, controlling the output of the unit.  If you are wiring this unit up to something that doesn't have the proper harness, you can route this wire back to the battery terminal on the unit.  Though it's a viable solution, this is not the best way to hook it up because if there is any resistance in the battery wire, it may tend to run a bit hotter and overcharge a bit.

Testing the unit doesn't leave you many options.  Of course using a voltmeter across the battery terminals is the best way to check if it's working, reading a fully charged battery at 12.5 volts and then after starting the vehicle, it should read a volt higher.  Getting the alternator checked by a qualified technician is the best way to determine if it is good or not.  If the alternator is not charging, with the engine running, one test you can perform is to take a small screwdriver and poke it into the small 'D' shaped hole in the back of the unit (Illustrated below) to bypass the regulator, which will put the alternator into full charge.  The grounding tab is about 5/8 of an inch from the back surface of the unit.  Don't poke it in too far or you can hit the spinning rotor, damaging the unit!  You do have at least an inch of space before hitting other components.  While grounding that tab, if the alternator charges, then the internal regulator is bad and will need replaced!



Thursday, January 20, 2011

Alternators, Models & Design, Part 1, Delco 10DN

With this post, I'm starting a series of posts to help you identify the type and model of popular units and some advice on how to check them.  I however, will not be going into how to repair them.

I will start off with the Delco series of alternators and the earliest popular model, the 10DN.  The 10DN was the first widely used alternator on passenger cars and trucks, up until about 1971-72 and was an externally regulated unit, (no built in regulator)!






As you can see from the photos, it looks a lot like the next series of the most popular internally regulated units (next post) and though some of the parts are interchangeable, some are not.  The best way to identify this alternator is by looking at the back of the unit.


As you can see, the two wire plug in goes straight into the back of the unit and not around the edge like later units and is more squared.  You have, of course the 'BAT' or battery terminal on the left and a ground terminal 'GRD' on the right.  The ground is not often used as the alternator is internally grounded to the case.  There are however some applications where an isolated ground is used and that terminal is insulated from the case.

The two spade terminals where the wire plugs in, are the 'R' or stator terminal on the left and the 'F' or field Terminal on the right.  In most applications both of these wires go to the regulator.  The field terminal is where the regulator controls the output of the alternator.  Though it's not recommended, you can unplug these wires on the vehicle and get a short jumper wire and cross it over to the battery terminal, to check the alternator.  (Leave the battery wire connected!)  By doing this you are putting the alternator into full charge and run the risk of damaging a weak unit.  The battery terminal must have 12 volts going to it for the alternator to work.  If that wire does not show battery voltage then you have a wiring problem and need to trace it down!

To check to see if the brushes are functional, you can use an ohm meter to check for continuity from the field terminal to ground with the plug unplugged.  This won't tell you if the brushes are worn out or if the alternator is good.  It'll just tell you if that circuit is functional.

There are a couple of variations to this alternator, but are generally somewhat rare.  In a marine application, there are stud connections instead of spade terminals and it has an extension protruding from the rear bearing area.  There is also an agricultural application that has a mechanical tachometer drive, which is mounted on the back of the unit.  I've found these mostly on Allis Chalmers tractors, but have seen them on other applications.

There is also an optional external regulator available, that can be attached and bolted to the back of the unit, but it is generally more expensive than buying an internally regulated unit, so I don't do many of them.  The next series internally regulated unit is a better unit to work on anyway and is more economical too!

Wednesday, January 12, 2011

Need It Fixed Cheap!

In today's world of a declining economy, many people are forced to save money anyway they can.  This is also one of the reasons my business is off too.  I'm currently only working half days and closing my shop early in the afternoon to save on utility costs. 

Now I 'm getting more and more customers who say they need it fixed as cheap as possible.  They don't care if it's done right, just as long as it works for a while.  I really don't want to fix units that aren't properly repaired, because a lot of times they will come back to bite you.  So I usually state that by fixing it that way, I won't warrant any of my work on the unit, as some of the worn parts may damage my new ones.  On the other hand, if I want to fix it right and charge accordingly, I won't get the job or the money for the repair, because they don't have the money to spend.  So now I'm forced to take on more and more of these types of jobs.  Beggars can't be choosers!

Today I had a starter come in that the customer wanted fixed cheap.  The commutator on the armature was chewed up pretty bad and the brushes were worn out.  Those parts I had to fix!  The other parts that should have been replaced were the bushings, drive and solenoid.  The customer didn't want to replace those parts, due to the extra cost and they were still working and usable, so I reused them.  How long they will last is anyone's guess, but if the unit were mine, I would have replaced them.  Although, if I were in his financial condition, I might have done what he did!  So all I could do is repair it to his wishes and hope for the best! 

Tuesday, January 4, 2011

Does Checking Voltage Tell You If Your Alternator's Charging Properly?

In a word, No!

Now lets back up a second and say yes, you can tell if it is 'charging', but the question is, is it charging properly and does it have full capacity.  Checking voltage alone won't give you those answers.  You need to know the current output with and without a load to tell you if it is working properly.  There are even more sophisticated testing procedures that can be done, that tells you condition of various internal parts, but I won't go into that.

Usually I tell my customers, after I've checked or repaired their unit, to charge their battery fully.  Then check the voltage of the fully charged battery across the terminals and it should read about 12.5 volts.  Then start the vehicle and check again and the voltage should read about a volt higher or 13.5 volts.  Once the alternator has re-charged the battery, for what the starter used starting the vehicle, and if all unnecessary electrical loads turned off, voltage should approach the regulators set point of around 14.5 volts.  If you are still only reading battery voltage, then you may have a wiring problem, which is not connecting or energizing the alternator with the system. 

Getting back to our example of why checking voltage won't tell you what the alternators condition is, here is why.  On two separate but identical vehicles with 100 amp alternators, with regulators that have a set point at 14.5 volts, one of them is putting out 13.0 volts and when the current output is checked, it is shown to be putting out 20 amps.  The second vehicle is also putting out 13.0 volts, but the amperage output is 90 amps.  Both of these alternators are charging, but the one only putting out 20 amps is defective.  Why?  Because at a lower voltage, the alternators current output should be much higher to help build the battery closer to the regulators set point.  This lower output would indicate a bad stator or bad diodes in the rectifier and the alternator would need repaired.

I might also mention that if that 100 amp alternator is putting out 90 amps continues output and doesn't regulate down, it indicates either a bad regulator or a weak or bad battery.  If it is the battery, that alternator or it's replacement won't last long, because even though it is a 100 amp alternator, it can not continually run at that high of an amp output very long without burning up!  Alternators are only designed to run continuously at 75 percent of their rated capacity.  So a 100 amp alternator can only produce 75 amps of continuous output.

So just checking the voltage output may tell you that the alternator is working, but won't tell you if it is good!